3116 TA 300hp heat exchanger temps? Port running hotter than Stbd.

[inquisitivej]

My port engine runs a few degrees hotter than starboard according to the gauges at both helm and fly bridge (doing 1800 rpms 175 degrees starboard and ~178 for port). Infrared thermometer says the engine blocks are pretty much the same temp. The engine heat exchanger (as opposed to the transmission oil heat exchanger) on the port read 10 to 15 degrees hotter than the starboard. I've not yet taken the temp of both transmission oil exchangers (on the todo list next time I'm underway for long enough). The flow rate out of the exhaust is unchanged from what is normal.

I've noticed no starting problems. No responsiveness or power issues of any sort. They perform almost identically. The port engine alternator charges the house battery bank so its alternator load is very often higher than starboard (only charges starting batteries).

I pulled the impeller out of the raw water pump. It was intact and in good shape as was the cam that forces the fins to flex (I've been told those can break or wear out and are often missed as a cause of cooling issues).

The coolant tank is full, the coolant looks uncontaminated and the same color as the starboard engine. The coolant pump belt is fine and same tension as starboard engine. All 4 heat exchangers (2 main and 2 transmission oil) were removed and serviced 3 years ago (not that long ago!).

The sea strainer is clean. Zincs are checked/replaced every 3 months.

I've discovered the raw water pumps are slightly different on each engine. The port engine pump is the white one in the pictures, the unpainted in the starboard. They use the same impeller, which means the GPM should be the same, yes? The raw water pumps on the 3116 are gear driven (can't imagine the gear size is different given the fixed attachment point of the pump (not like you could use a smaller or larger gear unless you could mount the pump in different spot).

These are very well maintained engines with around 3300-3400 hours on them. The prior owners did a great job, only been mine since December.

During survey haulout no issues were noticed with the thru-hull inlet for the port engine raw water intake.

I'm reluctant to take apart the heat exchangers since they were serviced so recently and I'm told they are quite hard to reassemble and have be water tight. I have not yet pulled supply side hose of the oil heat exchanger to see if i can see anything in there blocking up the whole flow of water. Seems thats the next easiest thing to check that could be playing a role. Seems low probability to me given the way water flows in this system. If something is blocking in the oil exchanger it would have had to make it past the impeller, through the engine exchanger, and to the intake side of the oil exchanger. Maybe the diameter of the tubes in the oil exchanger are much narrower?

If you have a 3116 TA 300hp I would love to hear what your infrared readings are for the main exchanger and the transmission exchanger. IIRC, on the starboard it was in the 115 degree range and the port was 125-130 ish range.

Once engines are up to temp I see no obvious exhaust from either engine while cruising at 1800rpm or when at idle after cruising.

Its not a problem, and maybe its normal? My concern is that its the beginning stages of something that *could* become a big deal, so I'm trying to listen to what the engine is telling me so it never becomes a surprise or big deal.

Hopefully thats enough detail to get some good suggestions from all of you and some good questions. I'm sure there are 3116 experts here, I am a novice still.

Thanks in advance!

 

[heysteve]

Getting to know a new boat is always exciting! From what you've described, it doesn't seem like anything to crazy is going on but understanding the current state of things is always a good idea. So kudos for that!

The one thing that does seem kinda off is the difference in heat exchanger temps give that both blocks are the same temps. Did you measure the temperature at the heat exchanger at the same place on both sides? It's important because the engine coolant coming into it will be warmer than the coolant going out.

If you don't already have one, a thermal imaging camera can be a good way to visualize the heat flow in your engine. Some also allow you to take pictures so you can have a record of it over time.

The gauge reading difference isn't a big deal and is likely just a variation in the sending unit.

 

[High Wire]

Are these gauges digital? 3 degrees F difference is well within normal variance for normal boating instruments. 3F is less than the width of the needle of a typical analog gauge.

 

[ranger58sb]

'm reluctant to take apart the heat exchangers since they were serviced so recently and I'm told they are quite hard to reassemble and have be water tight. I have not yet pulled supply side hose of the oil heat exchanger to see if i can see anything in there blocking up the whole flow of water. Seems thats the next easiest thing to check that could be playing a role. Seems low probability to me given the way water flows in this system. If something is blocking in the oil exchanger it would have had to make it past the impeller, through the engine exchanger, and to the intake side of the oil exchanger. Maybe the diameter of the tubes in the oil exchanger are much narrower?

If you have a 3116 TA 300hp I would love to hear what your infrared readings are for the main exchanger and the transmission exchanger. IIRC, on the starboard it was in the 115 degree range and the port was 125-130 ish range.

15° variance at the heat exchangers seems different enough to warrant research.

You might try flushing the port engine with something like Barnacle Buster or Rydlyme... to see if maybe that makes any difference without having to disassemble...

I could imagine the partial remains of a pencil zinc or old impeller vanes or whatever being in there... maybe impeding flow enough to make a temp difference but not enough to be visible in the discharge. If temp drops, could have been a zinc. If temp doesn't drop, could be impeller bits and disassemble might end up being the right approach.

???

-Chris

 

[BB-marine]

A few thoughts that I have. The gauge readings seemed to be normal. It is not unusual to see a fluctuation in engine operating temperature of 5F Degree when comparing a thermistor sensor and gauge. Checking the temperature with a IR gun in different locations on the engine will be more accurate if you have concerns. I would not be concerned with a 3F degree differential between a port and starboard engine.

The heat exchanger temperature will change with ambient water temperature. Example: If I am running my marine engine in Florida waters the exchanger temperature average temperature may be higher than if I am operating the engine in the PNW where water ambient temperatures are lower. The proper test for a heat exchanger is check the temperature of the exchanger at the intake side of the exchanger (up stream raw water intake side) then check the temperature at the exhaust side of the exchanger ( down stream raw water discharge side) . The temperature differential should be between 10F to 20F differential upstream to downstream. If it is higher there may be an obstruction in the exchanger, obstruction in the reverse gear cooler if down stream of the exchanger, obstruction in the exhaust elbow. A reduction in raw water flow from a raw water pump, through hull.......

If the exchanger was serviced it may be clean but at some point when cleaning and testing the exchanger a tube may have been determined to be defective, leaking and plugged. 10% of the tubes can be plugged and the exchanger will still function properly. If the port exchanger has a few tubes permanently plugged it may cause a slight change in exchanger cooling . A thermostat can cause a difference in engine temperature of 3F degrees . Thermostats have an accuracy close to set point but 3F degree would be acceptable in my opinion.

It is a good idea to watch this discrepancy in temperature but I would not get to concerned. I would recommend recording operating temperatures in your log and if you see a slow increase in operating temperature and a larger differential between the starboard engine and port or a increase in port engine exchanger and exhaust riser (at the mixer location) continue to troubleshoot.

You stated you checked the volute eccentric for wear. The end cover and volute interior wear plate if worn will reduce water flow. Air can get trapped and the pump can loose prime if worn bad enough. Any wear in the volute will reduce flow.
Brian

 

[inquisitivej]

Getting to know a new boat is always exciting! From what you've described, it doesn't seem like anything to crazy is going on but understanding the current state of things is always a good idea. So kudos for that!

The one thing that does seem kinda off is the difference in heat exchanger temps give that both blocks are the same temps. Did you measure the temperature at the heat exchanger at the same place on both sides? It's important because the engine coolant coming into it will be warmer than the coolant going out.

If you don't already have one, a thermal imaging camera can be a good way to visualize the heat flow in your engine. Some also allow you to take pictures so you can have a record of it over time.

The gauge reading difference isn't a big deal and is likely just a variation in the sending unit.

I measured the heat exchangers at the same position. However I just realized I measured the blocks from different locations (one from port one from stbd). Another thing for me to check next time I’m out.

What do you think about the different pumps playing a role?

I haven’t looked at IR cameras, last I checked they were super pricey, but that was a while ago, maybe better now.

 

[inquisitivej]

Are these gauges digital? 3 degrees F difference is well within normal variance for normal boating instruments. 3F is less than the width of the needle of a typical analog gauge.

Yes, analog. The needs are not that wide on these gauges. The point is less about the gauges and more about the heat exchangers differences.

What temp variance on the gauges would get you concerned? 5? More?

 

[inquisitivej]

A few thoughts that I have. The gauge readings seemed to be normal. It is not unusual to see a fluctuation in engine operating temperature of 5F Degree when comparing a thermistor sensor and gauge. Checking the temperature with a IR gun in different locations on the engine will be more accurate if you have concerns. I would not be concerned with a 3F degree differential between a port and starboard engine.

The heat exchanger temperature will change with ambient water temperature. Example: If I am running my marine engine in Florida waters the exchanger temperature average temperature may be higher than if I am operating the engine in the PNW where water ambient temperatures are lower. The proper test for a heat exchanger is check the temperature of the exchanger at the intake side of the exchanger (up stream raw water intake side) then check the temperature at the exhaust side of the exchanger ( down stream raw water discharge side) . The temperature differential should be between 10F to 20F differential upstream to downstream. If it is higher there may be an obstruction in the exchanger, obstruction in the reverse gear cooler if down stream of the exchanger, obstruction in the exhaust elbow. A reduction in raw water flow from a raw water pump, through hull.......

If the exchanger was serviced it may be clean but at some point when cleaning and testing the exchanger a tube may have been determined to be defective, leaking and plugged. 10% of the tubes can be plugged and the exchanger will still function properly. If the port exchanger has a few tubes permanently plugged it may cause a slight change in exchanger cooling . A thermostat can cause a difference in engine temperature of 3F degrees . Thermostats have an accuracy close to set point but 3F degree would be acceptable in my opinion.

It is a good idea to watch this discrepancy in temperature but I would not get to concerned. I would recommend recording operating temperatures in your log and if you see a slow increase in operating temperature and a larger differential between the starboard engine and port or a increase in port engine exchanger and exhaust riser (at the mixer location) continue to troubleshoot.

You stated you checked the volute eccentric for wear. The end cover and volute interior wear plate if worn will reduce water flow. Air can get trapped and the pump can loose prime if worn bad enough. Any wear in the volute will reduce flow.
Brian

Thanks for the reply! The 10-20 degree drop from one side to the other of the exchanger is very helpful.

 

[heysteve]

I measured the heat exchangers at the same position. However I just realized I measured the blocks from different locations (one from port one from stbd). Another thing for me to check next time I’m out.

What do you think about the different pumps playing a role?

I haven’t looked at IR cameras, last I checked they were super pricey, but that was a while ago, maybe better now.

Give they use the same impeller, it seems unlikely the waterflow would be different.

Notwithstanding the difference in block temps, my guess is that the engines have different temperature thermostats. Just by coincidence, I recently order thermostats for my Cat 3208 N from the Cat dealer and received thermostats that are 10 degrees hotter. It's certainly compatible but the marine engine uses a cooler thermostat.

 

[inquisitivej]

Thanks!

If it’s thermostat related I should notice a clear difference in the coolant line infrared temps.

 

[High Wire]

Yes, analog. The needs are not that wide on these gauges. The point is less about the gauges and more about the heat exchangers differences.

What temp variance on the gauges would get you concerned? 5? More?

At least 10F if verified by an IR instrument. Analog boat gauges are just not that precise. It's an upward trend or large unexplained change that would get me concerned.

 

[Sax]

Give they use the same impeller, it seems unlikely the waterflow would be different.

Notwithstanding the difference in block temps, my guess is that the engines have different temperature thermostats. Just by coincidence, I recently order thermostats for my Cat 3208 N from the Cat dealer and received thermostats that are 10 degrees hotter. It's certainly compatible but the marine engine uses a cooler thermostat.

Did you use the hotter thermostats or exchange them for lower ones? When I replaced my regulators (Cat speak for thermostats) a few years ago, I was told that Cat switched to hotter thermostats (192 degrees) to keep oil temperatures higher to better burn off impurities in the oil. I have seen various articles by Steve D’ and Max Parker about the need to maintain oil temps (not water) up around 200 degrees. Just curious what you ultimately decided to do with your engine.

 

[heysteve]

Yeah... I haven't drummed up the motivation to replace them yet as the heat exchanger needs to be removed for access and gallons of coolant drained etc. I will probably use the hotter regulators for the reason you say - especially since I typically only run at 15-1800 RPM (2400 is 80%).

 

[Sax]

I typically cruise at 1300 - 1500 RPM, 8 - 9 knots, with twin Cat 3208 TAs. The boat starts pushing up against hull speed around 1600 RPM. The hotter thermostats make sense for the way I operate the boat.

Getting back to Inquistivej’s original concern, my two engines with 4500 hours, operate with a water temperature difference of about six degrees on the flybridge gauges and 0 degrees difference at the lower helm. Both gauges use the same sender. When measured in various locations with a handheld IR gun, water temps are a couple degrees different between engines.

As others have mentioned, this type of gauge error is less important than looking for changes in your normal readings, either occurring quickly or over time. A consistent three degree difference in your two engine water temperatures would not concern me at all.

 

[luna]

I think IR guns are good tools, but I would not rely on them to be very accurate.

For about $100 you can get from Amazon or others a 4 Channel Data Logger (looks like a multimeter) and a handful of Type K Thermocouples which are just a wire with what looks like a pin head at the business end.

Use some foam weather stripping and tape the pin head onto the heat exchangers and with the logger read the temperatures accurately to within about 2º C.

If you want more accuracy you could place the thermocouple in boiling water (not touching the pot) and read what it shows as the temperature. Record what ever the difference is from 100º C and adjust your records to suit. Do the same thing in ice water if you want.

 

[Greg QS]

My port engine runs a few degrees hotter than starboard according to the gauges at both helm and fly bridge (doing 1800 rpms 175 degrees starboard and ~178 for port). Infrared thermometer says the engine blocks are pretty much the same temp. The engine heat exchanger (as opposed to the transmission oil heat exchanger) on the port read 10 to 15 degrees hotter than the starboard. I've not yet taken the temp of both transmission oil exchangers (on the todo list next time I'm underway for long enough). The flow rate out of the exhaust is unchanged from what is normal.

I've noticed no starting problems. No responsiveness or power issues of any sort. They perform almost identically. The port engine alternator charges the house battery bank so its alternator load is very often higher than starboard (only charges starting batteries).

I pulled the impeller out of the raw water pump. It was intact and in good shape as was the cam that forces the fins to flex (I've been told those can break or wear out and are often missed as a cause of cooling issues).

The coolant tank is full, the coolant looks uncontaminated and the same color as the starboard engine. The coolant pump belt is fine and same tension as starboard engine. All 4 heat exchangers (2 main and 2 transmission oil) were removed and serviced 3 years ago (not that long ago!).

The sea strainer is clean. Zincs are checked/replaced every 3 months.

I've discovered the raw water pumps are slightly different on each engine. The port engine pump is the white one in the pictures, the unpainted in the starboard. They use the same impeller, which means the GPM should be the same, yes? The raw water pumps on the 3116 are gear driven (can't imagine the gear size is different given the fixed attachment point of the pump (not like you could use a smaller or larger gear unless you could mount the pump in different spot).

These are very well maintained engines with around 3300-3400 hours on them. The prior owners did a great job, only been mine since December.

During survey haulout no issues were noticed with the thru-hull inlet for the port engine raw water intake.

I'm reluctant to take apart the heat exchangers since they were serviced so recently and I'm told they are quite hard to reassemble and have be water tight. I have not yet pulled supply side hose of the oil heat exchanger to see if i can see anything in there blocking up the whole flow of water. Seems thats the next easiest thing to check that could be playing a role. Seems low probability to me given the way water flows in this system. If something is blocking in the oil exchanger it would have had to make it past the impeller, through the engine exchanger, and to the intake side of the oil exchanger. Maybe the diameter of the tubes in the oil exchanger are much narrower?

If you have a 3116 TA 300hp I would love to hear what your infrared readings are for the main exchanger and the transmission exchanger. IIRC, on the starboard it was in the 115 degree range and the port was 125-130 ish range.

Once engines are up to temp I see no obvious exhaust from either engine while cruising at 1800rpm or when at idle after cruising.

Its not a problem, and maybe its normal? My concern is that its the beginning stages of something that *could* become a big deal, so I'm trying to listen to what the engine is telling me so it never becomes a surprise or big deal.

Hopefully thats enough detail to get some good suggestions from all of you and some good questions. I'm sure there are 3116 experts here, I am a novice still.

Thanks in advance!

Ok I am not an expert on the engine you have. However all the cooling system work in the same way. You said you just had the HE done on both engines, right? What about the fuel and trans coolers? They are before the HE and either can cause a restriction and create the problem you are having. When was the intercooler done last? Can you measure the load on the engine or fuel burn accurately? A wacked prop can put more load on an engine, thus more heat, more load, more fuel consumption and create you symptoms.

 

[inquisitivej]

Did you use the hotter thermostats or exchange them for lower ones? When I replaced my regulators (Cat speak for thermostats) a few years ago, I was told that Cat switched to hotter thermostats (192 degrees) to keep oil temperatures higher to better burn off impurities in the oil. I have seen various articles by Steve D’ and Max Parker about the need to maintain oil temps (not water) up around 200 degrees. Just curious what you ultimately decided to do with your engine.

They have thermostats that came with them when I bought the boat in December. Have not changed them and don’t know which ones they have. I’ve never seen these engines go above 180 (usually 175ish) on the helm gauges.

It’s a really interesting idea and I can imagine lots of pros and cons to be considered in this choice. Something else to add to the list to research.

 

[inquisitivej]

Ok I am not an expert on the engine you have. However all the cooling system work in the same way. You said you just had the HE done on both engines, right? What about the fuel and trans coolers? They are before the HE and either can cause a restriction and create the problem you are having. When was the intercooler done last? Can you measure the load on the engine or fuel burn accurately? A wacked prop can put more load on an engine, thus more heat, more load, more fuel consumption and create you symptoms.

The water raw water flow on these is pump to main engine exchanger to transmission hex to exhaust. My understanding is the coolant that also flows through the jacket of the main engine hex is what is involved with intercooler and engine block cooling.

I don’t know when the intercooler was last done. All 4 exchangers (2 on each engine) were done 3 years ago.

 

[Greg QS]

Intercoolers are after you HE for the engine. They cool the air from the turbo that is entered into you engine. It makes the air more dense oxygen rich witch increases combustion. The intercooler creates condensation on the air side and get plugged with a mixture of oil and water condensation. This plugs the air side , Increases the air temp into the engine. increases exhaust temps, increases the work of the HE on the engine.

In salt water Cummings ( my engines ) recommend a 2 year service on the HE, oil, and trans coolers. I flush with fresh water and do a 3 year tear down service. Cummings recommends 1000hr service on the intercooler. I really don't believe in using hours for service. A buddy of mine was ready for his 1000hr service. 10years since the last service. He blew up the engine before the service. Time is a better gauge. I think I am going to do them again at 3 years to get a gauge on there condition. I did a full cooling service all coolers and HE and intercooler when I purchased the boat my first winter in 2023 to have a 0 hour point on the service. My next service will be this coming winter in 2026-26 .

I do not believe in Barnacle buster. Does it work ? yes. But there is no way to pressure test the system. If you create a hole in the intercooler you get salt water on the air side and destroy you engine. I used it on my last boat. The winter after using it, my coolant leaked out into the sea water side. This was due to the cleaning of the HE opened up a hole and allowed the antifreeze and the salt water to mix. It went un noticed until the winter when my coolant level dropped while out of the water. If the intercooler had that problem, I would have destroyed the engine.

I would recommend to do a full cooling service. All coolers and the intercooler. You will get a good gauge on the condition of the coolers since its been 3 years. Get the intercooler done ! The biggest problem on the cats is the disassembly of the intercooler due to corrosion because of the salt water. There have been a bunch of posts of people ruining there cooler because they could not get it apart.

 

[inquisitivej]

Intercoolers are after you HE for the engine. They cool the air from the turbo that is entered into you engine. It makes the air more dense oxygen rich witch increases combustion. The intercooler creates condensation on the air side and get plugged with a mixture of oil and water condensation. This plugs the air side , Increases the air temp into the engine. increases exhaust temps, increases the work of the HE on the engine.

In salt water Cummings ( my engines ) recommend a 2 year service on the HE, oil, and trans coolers. I flush with fresh water and do a 3 year tear down service. Cummings recommends 1000hr service on the intercooler. I really don't believe in using hours for service. A buddy of mine was ready for his 1000hr service. 10years since the last service. He blew up the engine before the service. Time is a better gauge. I think I am going to do them again at 3 years to get a gauge on there condition. I did a full cooling service all coolers and HE and intercooler when I purchased the boat my first winter in 2023 to have a 0 hour point on the service. My next service will be this coming winter in 2026-26 .

I do not believe in Barnacle buster. Does it work ? yes. But there is no way to pressure test the system. If you create a hole in the intercooler you get salt water on the air side and destroy you engine. I used it on my last boat. The winter after using it, my coolant leaked out into the sea water side. This was due to the cleaning of the HE opened up a hole and allowed the antifreeze and the salt water to mix. It went un noticed until the winter when my coolant level dropped while out of the water. If the intercooler had that problem, I would have destroyed the engine.

I would recommend to do a full cooling service. All coolers and the intercooler. You will get a good gauge on the condition of the coolers since its been 3 years. Get the intercooler done ! The biggest problem on the cats is the disassembly of the intercooler due to corrosion because of the salt water. There have been a bunch of posts of people ruining there cooler because they could not get it apart.

I could have sworn I read and traced the lines and came to the conclusion the aftercooler (not intercooler (3116 TA)) was coolant cooled, not raw water cooled. Hmmm....

 

[luna]

I think a Cat 3116 TA (Turbocharged and Aftercooled) @ 300 HP is a low enough output (45hp/litre) that jacket water is the fluid that runs through the aftercooler. My Cat 3408, with the same output per litre has the aftercooler cooled by the jacket water.

This virtually eliminates the issues that Cummins and other raw water cooled aftercoolers exhibit.

The OP has already noted that the raw water is in through the pump, then the engine and gear's oil coolers and then out the shower heads. I think he has that right.

I would recommend you try to resolve the anomaly of an IR gun's temperature reading being different from gauge readings before you rip into the engine, potentially chasing ghosts.

This does not mean that cooler service is to be neglected.
The engine's cooler if it has removable end caps can be mechanically cleaned and tested in place, as long as reasonable access exists. I doubt it, but do not know for sure if the tube bundle is removable. The gear's coolers if they are the same design can also be done without removal. Otherwise replace them if suspect.
The aftercooler will need to be removed to clean the fins with hot water and detergent, multiple times, then tested. It should not be hard to do as there will be no salt water corrosion.
All of the above is cheap and easy to do, it just takes time.

Once done, plumb in a fresh water rinse system on the raw water side and you can extend the time between cleanings to about twice the normal interval.

 

[High Wire]

If the OP really wants to chase this, one easy thing to try is swapping the gauge senders between engines to show if the temp difference moves to the other engine or not. One advantage of twin engines.

 

[inquisitivej]

I think a Cat 3116 TA (Turbocharged and Aftercooled) @ 300 HP is a low enough output (45hp/litre) that jacket water is the fluid that runs through the aftercooler. My Cat 3408, with the same output per litre has the aftercooler cooled by the jacket water.

This virtually eliminates the issues that Cummins and other raw water cooled aftercoolers exhibit.

The OP has already noted that the raw water is in through the pump, then the engine and gear's oil coolers and then out the shower heads. I think he has that right.

I would recommend you try to resolve the anomaly of an IR gun's temperature reading being different from gauge readings before you rip into the engine, potentially chasing ghosts.

This does not mean that cooler service is to be neglected.
The engine's cooler if it has removable end caps can be mechanically cleaned and tested in place, as long as reasonable access exists. I doubt it, but do not know for sure if the tube bundle is removable. The gear's coolers if they are the same design can also be done without removal. Otherwise replace them if suspect.
The aftercooler will need to be removed to clean the fins with hot water and detergent, multiple times, then tested. It should not be hard to do as there will be no salt water corrosion.
All of the above is cheap and easy to do, it just takes time.

Once done, plumb in a fresh water rinse system on the raw water side and you can extend the time between cleanings to about twice the normal interval.

On the IR readings, just to be clear, the thing that I'm focused on is the 10-15 degree heat exchanger housing temp difference between the two engines. I'm less focused on the engine gauge temp variance. I'm treating that more as a possible leading indicator that there is something to inspect... which seems to be true, it led me to the hex temp variance.

the tube bundle on the main exchanger is removable and there are endcaps. I'm told by the prior owner that is very difficult to get it back together and have it not leak. I've never done it myself so trusting he is more right than he is wrong. THough I still think only 3 years since fully removed, serviced, and tested by Seattle Radiator seems a surprisingly short period. Maybe my expectations just need to be adjusted that this is a more frequent aspect of maintenance than I thought.

The transmission oil exchanger does not have removable endcaps. I am thinking I could pull the hoses off and see if there is any clear obstruction on the input side of the hex. To clean/service them I'm told the radiator shop has unsolder the endcaps to get to the tube bundle. Unclear if that bundle is removeable from the jacket.

Can you tell me more about what you would expect a "fresh water rinse system" too look like? Are you talking about adding some sort of a "t" with a hosebib and valve on the raw water input side (upstream of the pump or between pump and hex)? I assume I would just let it follow the exhaust path and not add some sort of "t" on that side?

Also, without a haulout, any thoughts on back flushing from the intake side of the water pump and through the grocco strainer and through-hull? I guess I just gin up some sort of pvc fittings to connect to a hosebib to I can backflush the lower part of the raw water path? Maybe the whole thing is just something caught in the input hose or input side of the grocco (which where isn't much to, its directly mounted on the hull, so seems unlikely).

 

[inquisitivej]

I think IR guns are good tools, but I would not rely on them to be very accurate.

For about $100 you can get from Amazon or others a 4 Channel Data Logger (looks like a multimeter) and a handful of Type K Thermocouples which are just a wire with what looks like a pin head at the business end.

Use some foam weather stripping and tape the pin head onto the heat exchangers and with the logger read the temperatures accurately to within about 2º C.

If you want more accuracy you could place the thermocouple in boiling water (not touching the pot) and read what it shows as the temperature. Record what ever the difference is from 100º C and adjust your records to suit. Do the same thing in ice water if you want.

data driven approach, I like it. can you post a link to the sort of thing you are talking about? I'm unfamiliar with these devices.

 

[luna]

I will respond to your questions once I get back to my laptop as I don’t type well on phones.

One thing you could try that costs nothing is to shot your spots on the HE that showed a 15 degree difference with the engine cold, eg. not run for a few days. Same difference in temp?

Then I would apply black tape or flat black paint to a small patch on each HE and shoot again, both cold and hot. Make sure the black spot exceeds the size of the guns field of view.

 

[inquisitivej]

I will respond to your questions once I get back to my laptop as I don’t type well on phones.

One thing you could try that costs nothing is to shot your spots on the HE that showed a 15 degree difference with the engine cold, eg. not run for a few days. Same difference in temp?

Then I would apply black tape or flat black paint to a small patch on each HE and shoot again, both cold and hot. Make sure the black spot exceeds the size of the guns field of view.

I appreciate the engagement and the answers when laptop available.

Not sure where you are going with the black surface. I have two nearly identical engines, both heat exchangers painted the same color, measurements taken in the same manner (proximity and attitude of the IR gun), and I'm comparing the two. Such a relative measure shouldn't benefit from the color of the surface I'm zapping, right? I am not sure I'm following where you are going.

I do see the point in a baseline measurement when they are both dead cold, a good idea and not something I've done (yet).

 

[luna]

Amazon has a number of Data Loggers and Thermocouplers available. Here is one with 4 probes for $76

Amazon.com

I make no representations as to the accuracy of this instrument or the probes. You can shop and make your choice as you see fit. Make sure that the probes have long enough wire on them so you can mount all 4 and not have to move the meter, it's easier.

Hopefully your new instrument confirms one of the 2 different temperature measurements that you have recorded.

The black tape/paint is as much a repeatable targeting aid as anything else, although without getting into a lot of undergrad physics, IR guns collect emitted thermal radiation and with that information, calculate a temperature. Different surfaces have different emissivities and that can effect the results. The tape or paint simply serves as a reasonable attempt to make the surfaces act the same.

Here is a 4 minute read to get your interest up.

https://www.lsop.colostate.edu/wp-content/uploads/sites/6/2018/04/InfraredThermometerTheory.pdf

The freshwater rinse of my raw water system starts at the lid of my 3" Groco strainer. The lid is large enough that I bored a hole through it and installed a 3/4" thru hull fitting, then a bronze 3/4" valve and brass garden hose fittings including a plug. I also installed a T at the low point of the gear cooler's plumbing and put in a valve and street elbow, that includes another plug. Valves, even closed ones should never be left open ended.

Finally I installed a T and a valve in the 1" raw water hose that feeds the genset's strainer. Yep, another plug.

Operationally, it is simple.

I connect a charged garden hose to the fitting on the Groco strainer and open the valve. After I remove the plug from the gear cooler's plumbing, I open the valve and what salt water that was in the engines raw water system runs out of the street elbow into a 5 gallon bucket. It's about 3 gallons of salt water.

I then close the engine's 3" thru hull valve and that forces the still running fresh water up the raw water circuit through the raw water pump, the heat exchanger and out the gear cooler plumbing's open valve and elbow into the bucket.
The bucket would overflow quickly if it wasn't for that fact that I use a 3/4" hose connected to the T in the genset's plumbing and by throwing a couple of valves, suck the water out of the bucket once I start the genset. Garden hose flow (wide open) is about the same as the genset's pump demand. Life is good.

I run about 25 gallons of fresh water through each of my engines and rinse the 2 gensets, which only run as they are a convenient pump and they need a rinse anyway, in about 20 minutes.

I can do this without potentially causing harm (by forcing fresh water through the raw water pump's seals) to the "at rest" main engines because my raw water pump is not a positive displacement pump and as a result water runs right through it, almost unimpeded. Your raw water pump, if it has a flexible impeller will likely not allow this.
You also need an exhaust system that will drain with the engines at rest. No lift muffler allowed. Mine drains.

You will likely have to start your engines, run them only at idle and suck fresh water from a bucket by way of hose with a connection at the strainer. That way almost all of the raw water circuit is left with fresh water in it.
If you freeze during the winter, you can also install cheap Vodka antifreeze the same way.

Backflushing the raw water circuit has the same kind of problems, you do not want to pressurize the raw water pump and force water through the seals and into the crankcase. You can do it, just first isolate the engine from the circuit that you pressurize.
I would think that if there was a blockage in the raw water circuit to such a degree that my coolant was running 10 - 15º hotter than an unblocked sister engine, the exhaust piping of the blocked engine would be running quite a bit hotter than the unblocked engine. My fibreglass exhaust piping runs at 130º F. if I'm doing 900 RPM and about 90º F. if I'm at 2000 RPM. Water flow, by way of a spinning pump rules.

Have you measured your exhaust piping temperatures while underway?

 

[C lectric]

E Bay offers numerous laser pointer temperature guns as do, often, local autoparts shops and hardware shops.

Yes you can spend a LOT of money if wished but one does not have to.
The biggest cause of poor readings is not reading/understanding or paying attention to instructions.
Almost all of these guns have a usefull range for readings. To far away means averaging the temp of a too large area. Not Good. However the farther it can read accurately the better. Some of these guns allow only a few inches , some up to a couple of feet. so pay attention to its use AND your choice and needs.

I paint a FLAT black spot on the areas I want / need to check especially if temp. checks are needed somewhat frequently.
Readings on flat black surfaces are better than shiny surfaces BUT NOT HOSES even though black.

 

[DennisB1]

Getting to know a new boat is always exciting! From what you've described, it doesn't seem like anything to crazy is going on but understanding the current state of things is always a good idea. So kudos for that!

The one thing that does seem kinda off is the difference in heat exchanger temps give that both blocks are the same temps. Did you measure the temperature at the heat exchanger at the same place on both sides? It's important because the engine coolant coming into it will be warmer than the coolant going out.

If you don't already have one, a thermal imaging camera can be a good way to visualize the heat flow in your engine. Some also allow you to take pictures so you can have a record of it over time.

The gauge reading difference isn't a big deal and is likely just a variation in the sending unit.

 

[Lepke]

Learning and maintaining you engines is great.
Cutting to the chase, a 3° difference between a pair of twins, anywhere doesn't mean there's a problem.
As others said the gauges or senders could be the cause. If you're set on doing something unnecessary buy a mechanical gauge. Run on one engine and the next day on the other. Even if you still have a 3° difference you could spend thousands chasing a non problem.
Worry about organisms growing in your diesel or changing oil on time. Both are a bigger problem.