Overheating 101

[firstbase]

Been running my new to me boat for a couple of months and everything engine-wise has sounded and looked good. Ford Lehamn SP135's which I run at 1500-1700 max. Both engine temps show at 180+- and oil pressure at 55. Port engine always reads a little higher, less than 5 degrees. Yesterday I decided to open it up and check out cooling temps at WOT. When I did the temps went to just under 200 on starboard and 200 on port. Took 3-4 minutes before I got an alarm which I assume was overheat on the port side. Throttled back and in a minute or two alarm cut out, temps dropped to normal and everything back to normal on the 1.5 hour cruise back home.

I assume this was caused by diminished water flow in coolant system as everything returned to normal when I backed off RPM's. Does a RW pump either work or not work, no in-between, for the most part?

Checked coolant levels in overflow tanks and both were fine.
No leaks or anything to note.
Strainers were cleaned 15 hours ago.
Impellers changed 6 hours ago.
New heat exchange/oil coolers, RW pumps 3-4 years ago before previous owner cruised loop and Bahamas.

My thought (inexperienced and little knowledge) is to flush raw water system with Barnacle Buster or similar although I haven't opened HE to see how clean/dirty they are yet. Looking at everything else in and on the boat/engines I believe they will be pretty clean but not sure.

Know this is all simple stuff for you guys and I would think that this situation is pretty normal or frequently heard. Have the standard engine alarms, nothing added. Is there an audible alarm difference between port overheat, starboard overheat or port/starboard oil pressure? Alarm goes off, just figure it out with the gauges?

Thanks for any comments.

 

[RT Firefly]

Greetings,
Mr. fb. What is your RPM at WOT?

 

[what_barnacles]

dont be surprised if you find impeller blades and even a broken zinc or two in the inlet side of the heat exchanger.

 

[firstbase]

FL135's show a rating of 2600 RPM's at WOT. I have original props on the boat and clean bottom when this happened and was slightly less than rated RPM's, 2500 or so.

 

[Rogerh]

If you have not cleaned your heat exchangers and oil coolers in 4 years I would suggest you start with that. The Barnacle buster may work but I would want to see how the exchangers look.

 

[firstbase]

dont be surprised if you find impeller blades and even a broken zinc or two in the inlet side of the heat exchanger.

Yes, will open the HE's up at first opportunity. Hope is is that simple, some bits and pieces. I did replace the impellers and zincs but nothing broken although it would seem to be hard to tell with a zinc. I'm not a WOT guy but just wanted to test out the cooling and make sure all was well and then go back to living a happy life at 1600. I think I am glad I did this??

 

[firstbase]

If you have not cleaned your heat exchangers and oil coolers in 4 years I would suggest you start with that. The Barnacle buster may work but I would want to see how the exchangers look.

Thanks. I can't find anything that indicates any service done since they were installed new. Will open them up and see. Only 3-4 years old so I would assume that they should be in good shape physically and just need a cleaning. That's not much age on these, correct? Zincs were replaced regularly...

 

[RT Firefly]

Greetings,
Mr. fb. "I think I am glad I did this??" You rebel you!

You say impellers were fine BUT what about bits that may have broken off previous to your ownership and still lodged in ?? places. Probably a ways down the analysis list but still a possibility. Just something to keep in mind.

I think your step by step inspection of the cooling system is warranted starting with the HE. Not a big deal to remove the end caps AND it's service experience that you can file in the memory banks. If nothing else, you're becoming more intimate with your mistress...

One more thing I will add. When you change zincs in the HE, put wrenches on BOTH the HE nut and the zinc holder. If you wrench on the zinc holder alone you may break the solder seal holding the nut on the HE. Don't ask how I Know...

 

[firstbase]

Yes, quite the rebel. At least that what all my sailboat friends say...! I would think that running WOT for 15 minutes every 50 hours or so would be an ok thing to do. Not so much for cleaning out cylinders and all that but to check cooling just like I did? No? I think I read that these engines have little need for high RPM "cleaning out"?

Thanks for the tip on the zinc install. I just wrenched them in never thinking about the solder seal (saying it like he actually knew anything about a solder seal). Also was SO proud to change the impellers all on my own just like a big boy I didn't think about needing to open up heat exchanger to check as nothing seemed amiss. Or aMrs. Either way. Now that I am learning a bit more I see the need to go back and look at several things no matter how pretty they are on the outside.

Going to hijack my own thread but the other thing I am trying to fix is the dipstick accuracy on my engines. I believe that the angle of the engines leads to the oil showing as low when it really isn't. Will mark it accurately when I change the oil in another 50 hours or so but for now I am showing this level on the pic. Both engines the same. Is this an adequate level for operation on the FL 135's? It seems you have the same ones maybe? Thanks for the comments.

 

[sunchaser]

1st base

You are correct, 101 digging wise to do. Do you know the last time coolant was changed? Also - Original props are no guarantee for correct props. The over heat alarm is an indicator of an issue whether exhaust elbows or ?? Some will argue, but too much prop can lead to full throttle over heat. While you're at it, check tachs against a photo tach.

 

[Pack Mule]

Is the bottom and props clean ?

 

[smitty477]

"Been running my new to me boat for a couple of months and everything engine-wise has sounded and looked good"


New to you boat after a couple of months perhaps consider these possibilities for a slower overheat at higher loads....
- Are the thru hulls loading up with growth
- Are you suction hoses new (thru hull to water pump hoses)
- Impeller is weak
- Impeller cam worn
- Blockage in one or more coolers
- Exhaust partially blocked
- Weak belt(s) on coolant side pump
- Thermostat(s) hung


Since it seems to affect both engines you can likely mostly rule out some of these by looking at the maintenance records and work most likely to least likely.


Additionally contributing factors could be engine related but you have not mentioned smoke or soot or water sheen at higher rpm so far.

 

[firstbase]

1st base

You are correct, 101 digging wise to do. Do you know the last time coolant was changed? Also - Original props are no guarantee for correct props. The over heat alarm is an indicator of an issue whether exhaust elbows or ?? Some will argue, but too much prop can lead to full throttle over heat. While you're at it, check tachs against a photo tach.

don't know of last coolant change and haven't learned how to check it to see if it needs it. A way to test the % of coolant left or something? Need to read up on how-to do that.

I will go back over the old receipts but I believe the exhaust elbows were also replaced when PO got ready to cruise. He did me some favors back then and didn't spare much $$$ getting ready. Just got a photo tach but couldn't use it this weekend as it was just wifey and me. I don't like going in engine room while running if there is nobody there for me to yell to. I know it looks relatively safe but I can't see waves, don't know whats going on and no way to contact anyone except cell phone maybe. But I bet you guys figured that out years ago....

I did check the props and they are the original ones designed/sized for the boat. Took off the 4 blade props as I have no business cruising around overpropped. Engines would only get to 2200 rpms with those. Had vibration which led me to have diver check props and they were not in good shape so had the originals, which were on board, tuned and balanced and then put back. Then had the same done to the 4 blades for spare. Nothing like an unplanned $2400 spend but hey it's only boat dollars right? Not like it is real money or anything....

 

[firstbase]

Is the bottom and props clean ?

Yes, everything cleaned about 2 weeks ago. Have it done monthly....

 

[firstbase]

"Been running my new to me boat for a couple of months and everything engine-wise has sounded and looked good"


New to you boat after a couple of months perhaps consider these possibilities for a slower overheat at higher loads....
- Are the thru hulls loading up with growth
- Are you suction hoses new (thru hull to water pump hoses)
- Impeller is weak
- Impeller cam worn
- Blockage in one or more coolers
- Exhaust partially blocked
- Weak belt(s) on coolant side pump
- Thermostat(s) hung

Since it seems to affect both engines you can likely mostly rule out some of these by looking at the maintenance records and work most likely to least likely.


Additionally contributing factors could be engine related but you have not mentioned smoke or soot or water sheen at higher rpm so far.

Thanks for a to-do list on this. Will start at top and work down. Water hoses appear brand new to almost brand new. No smoke to speak of at startup or running. Barely see a little for the first few minutes after starting. My wife saw none but I did is how little there is.

What temp should I be running at WOT? I would expect it to go up some but not sure what that should be. If I remember my reading correctly it seems that under 200 OK, over 200 and I need to do something immediately? If everything is working correctly should it stay at 180 or so?

Last, what would cause both engines to do this at the same time? Separate systems completely....maybe the same lack of good maintenance/cleaning of cooling system on both?

 

[RT Firefly]

Greetings,
Mr. fb. "...maybe the same lack of good maintenance/cleaning of cooling system on both?" OR both systems are clean and in the same condition AND you have yet another problem....In other words, I have no idea.

 

[smitty477]

"Last, what would cause both engines to do this at the same time? Separate systems completely....maybe the same lack of good maintenance/cleaning of cooling system on both?"


There are a number of things that tend to happen over time with both engines in a twin.
- thru hulls loading up with growth
- poor impellers (cracking vanes, soft from winterizing chemicals, etc)
- rwp cams being 'worn'
- buildup on raw water side of ''coolers''
- Silicate and impurity buildup on coolant side of X-changer
- Exhaust restrictions due to older/failing elbows

To mane a few.


"What temp should I be running at WOT? I would expect it to go up some but not sure what that should be."


Most of the boats I have owned the temps do not go up any from a fully warmed engine to WOT. On the ones that had some creep it was very small.

 

[bayview]

I have owned boats where the temps at low load were thermostat controlled but went up a bit at high load. sear water temps can make a difference.

If you have an engine heater water heater don't be surprised if that side is a little lower at above tstat temps.

On a new to you boat a full cooling system inspection is a good idea so you know where you are. Junk in the HE is common. Chemicals are not the answer only opening and inspecting and cleaning.

 

[sunchaser]

1st base

The fact that you put original props back on does not alter the fact they could be too big. This will indeed affect both engines. Sounds like the PO intentionally over propped with the 4 blades.

Ascertain full rated book RPM. Then armed with your photo tach, can you achieve that number? ( if only for 15 seconds so you don't set off alarms again) If yes, that is good. Now you can concentrate on the other noted over heat possibilities. If no, you have some decisions to make.

 

[kchace]

Yes, quite the rebel. At least that what all my sailboat friends say...! I would think that running WOT for 15 minutes every 50 hours or so would be an ok thing to do. Not so much for cleaning out cylinders and all that but to check cooling just like I did? No? I think I read that these engines have little need for high RPM "cleaning out"?

Thanks for the tip on the zinc install. I just wrenched them in never thinking about the solder seal (saying it like he actually knew anything about a solder seal). Also was SO proud to change the impellers all on my own just like a big boy I didn't think about needing to open up heat exchanger to check as nothing seemed amiss. Or aMrs. Either way. Now that I am learning a bit more I see the need to go back and look at several things no matter how pretty they are on the outside.

Going to hijack my own thread but the other thing I am trying to fix is the dipstick accuracy on my engines. I believe that the angle of the engines leads to the oil showing as low when it really isn't. Will mark it accurately when I change the oil in another 50 hours or so but for now I am showing this level on the pic. Both engines the same. Is this an adequate level for operation on the FL 135's? It seems you have the same ones maybe? Thanks for the comments.

The line you show on your picture is about where I have marked my dipsticks after added the correct measured amount of oil.

Ken

 

[kchace]

Yes, will open the HE's up at first opportunity. Hope is is that simple, some bits and pieces. I did replace the impellers and zincs but nothing broken although it would seem to be hard to tell with a zinc. I'm not a WOT guy but just wanted to test out the cooling and make sure all was well and then go back to living a happy life at 1600. I think I am glad I did this??

Its been my experience that a heat up like you experienced is due to not enough flow, which can be due to a restriction on the input side (Pickup, strainer, hoses) bad impeller, "dirty" heat exchanger, or even a constriction caused by corrosion at the outlet elbow into the exhaust mixer (although on that engine this is probably the least likely). The first places I would check are the main heat exchangers. Either way, you have gotten a number of excellent suggestions which I think will lead you to the fix.

FWIW - when I purchased my boat, I found a similar problem at WOT - the temps would keep climbing. In my case, it turned out to be that the main heat exchangers needed cleaning. I used Barnacle Buster with the bilge pump/bucket recirculating setup and it did an amazing job - and its easy! Now, temps climb maybe 5 degrees between cruise and WOT.

One other thing - you mention that the coolant levels in your overflow tanks are fine, but they may not even be working! It is common on the Lehman 135's for the small passage between the filler neck and the tube to the overflow to become blocked. I strongly suggest you take the pressure cap off the tank on the engine and verify your coolant levels. If the overflow tanks are working correctly, the coolant should be right to the top of the on-engine tank. A way to verify that the overflow tank system is working correctly is to verify the level in the overflow tank during a cold-hot-cold cycle. Check the level when the engines are completely cold, then check after the engines are thoroughly warmed up. Depending on the exact overflow tanks you have, the level in the overflow tanks should increase about a couple of inches, then go back to where it was after the engine completely cools down (like overnight). If this is not happening, they are not working.

BTW - your cruise temps and oil pressure are right on.

Ken

 

[firstbase]

Thanks for the advice. May help explain one thing...I went below after the heat up and looked at the overflow tanks and...they sure looked higher than normal. Several inches higher, both of them. I thought I was imagining things. Maybe thats a good sign. I will check them out again though. When you flushed your SP135's where did you connect the hoses for the circulation? I have read to connect immediately after the RW strainer but take the RW pump impeller out. Other say no no no connect AFTER the RW pump. On the other end I believe the RW dumps into the exhaust/muffler and that is where you pull it from on the other side, right at the connection to the exhaust? Not sure where else there would be to connect... Also read that reverse circulation works better than going with the normal RW flow....?

My bet is that I will find dirty HE's. I have had some indications that the PO may have let some maintenance things go after returning from cruising. He and wife had some significant health issues and it all got a bit too much for them. Flushing the cooling probably went by the wayside after they returned.

 

[firstbase]

The line you show on your picture is about where I have marked my dipsticks after added the correct measured amount of oil.

Ken

Thanks Ken. I believe the PO told me that he had "marked" one dipstick but not the other. I do see a small scrape of sorts right where the line is on one of them. However, I should go find him and BOING him over the head for not using a file or something more substantial to do it with! I do appreciate your real world SP135 knowledge.

I know the PO told me that he had two different dipsticks on either the trans or the engines but I'll be darned if I can tell as both sets look exactly the same. Maybe I dreamed it. Or he did.

 

[kchace]

Thanks for the advice. May help explain one thing...I went below after the heat up and looked at the overflow tanks and...they sure looked higher than normal. Several inches higher, both of them. I thought I was imagining things. Maybe thats a good sign. I will check them out again though. When you flushed your SP135's where did you connect the hoses for the circulation? I have read to connect immediately after the RW strainer but take the RW pump impeller out. Other say no no no connect AFTER the RW pump. On the other end I believe the RW dumps into the exhaust/muffler and that is where you pull it from on the other side, right at the connection to the exhaust? Not sure where else there would be to connect... Also read that reverse circulation works better than going with the normal RW flow....?

My bet is that I will find dirty HE's. I have had some indications that the PO may have let some maintenance things go after returning from cruising. He and wife had some significant health issues and it all got a bit too much for them. Flushing the cooling probably went by the wayside after they returned.

I have also read that reverse flow is better. I can imagine it might be and it can't hurt its just a bunch of tubes.

I definitely would NOT involve the raw water pump. Gunk can't collect inside it and I wouldn't want to risk possibly damaging it, no matter how small.

If you want to clean all three heat exchangers (not a bad idea) you can attach one hose to the front of the large heat exchanger and the other hose to the end of the transmission heat exchanger nearest the exhaust mixer. These are the SMALLER hoses only. The larger hoses are the other side of the system which is the antifreeze side. When you disconnect the smaller hose or take off the end cap only raw water will come out, it does not impact the engine's fresh water system. No need to mess with that.

One thing you definitely want to do first is check the "front" of the Engine Oil Cooler for bits of impeller and ocean "debris" because its first in line so thats where most of it will collect. It is still a good idea to check the input sides of both the other heat exchangers. The big one can get lots of zinc bits collected there and if they're really old you can still get quite a bit of ocean debris collected in the others too - more than enough to impact raw water flow. (On one of my old engine oil coolers you could hardly even see the tubes for all the ocean debris collected there)

If you use something like Barnacle Buster (Which worked REALLY well for me) you also need to remove any zincs - typically only one in the main heat exchanger. I bought the smallest Rule bilge pump to do mine. The only other items you need are some 1" plastic tubing and a 5 gallon bucket.

Ken

 

[FF]

IF heat exchanges can be opened at both ends,, a cleaning brush for a 22 usually does a great job.

 

[kchace]

Ooops, I gave the wrong locations for attaching circulating hoses for the purpose of running a cleaner like Barnacle Buster through all three heat exchangers at once. As installed on an FL135 engine, the raw water flows first through the engine oil HE, then the engine coolant HE (this is the big one), then the transmission HE, then out the exhaust. You can easily trace this from the raw water pump.

So to run a cleaner like Barnacle Buster through all three in *reverse flow* using a small bilge pump and a bucket, you should attach a hose from the bilge pump to the transmission oil cooler at the end nearest the exhaust, then a return hose to the front of the engine oil cooler HE that leads back to the bucket. Mix up a couple gallons of cleaner, drop the bilge pump and return line in the bucket and turn it on.

Because of this order of flow, it will also be the front of the engine oil HE that collects the most debris from broken impellers and ocean junk that gets by the sea strainer. You have to take the hose off the front of it to see in there and pick out any crap that has collected. I would suggest that its better to check and clean the front of the engine oil HE and coolant HE before running the cleaner through it.

Ken

 

[firstbase]

Thanks for the advice and directions. I was planning on opening up both ends of all three and rodding and cleaning thoroughly. Since the cleaning process is after and before the hoses to raw water intake and exhaust, what is done about them? Do they not get gunked up?

Slightly different are is the fresh water cooling. Understand that it doesn't gunk like the RW but I do read about flushing it as well when changing coolant? At this point, having found a couple of suspect things going on, I am going back to square one and doing everything from scratch so I know it was done and when. I believe there is a test to see whether or not the antifreeze is still in good shape? What is that test?

 

[smitty477]

"Slightly different are is the fresh water cooling. Understand that it doesn't gunk like the RW but I do read about flushing it as well when changing coolant?"


As long as the coolant side is not loaded up too much with things like silicate 'mud' and other contaminants on the outer side of the cooling bundles you can flush it like a car/truck radiator. If you are going to have the bundles all the way out it is much more effective to soak it to remove heavy deposits if they exist.
If you do just the flush any good quality flushing solution will work (like Prestone) but first make sure it is approved for the metals in your engine - in my case it needed to be aluminum safe for a few components and most of them are.
Drain the existing coolant fully / use the flushing agent mixed in the correct % - this will typically require more than one bottle of flush for the larger coolant capacity / follow the flush directions typically running the engine up to heat for maybe 15 minutes or more / then drain and fully rinse the flush two times / each time running up to heat to fully circulate the rinses.
It will all be on the flushing agents directions as well.

 

[kchace]

Thanks for the advice and directions. I was planning on opening up both ends of all three and rodding and cleaning thoroughly. Since the cleaning process is after and before the hoses to raw water intake and exhaust, what is done about them? Do they not get gunked up?

Slightly different are is the fresh water cooling. Understand that it doesn't gunk like the RW but I do read about flushing it as well when changing coolant? At this point, having found a couple of suspect things going on, I am going back to square one and doing everything from scratch so I know it was done and when. I believe there is a test to see whether or not the antifreeze is still in good shape? What is that test?

The exhaust outlet on a 135 is stainless steel and they usually last a very long time, But its not a bad idea to pull off the exhaust hose every few years to give them a look. If there is any internal accumulation on the hoses I've never heard of it getting thick enough to be a problem. Of greater concern (to me at least) is how old are those hoses and what condition they are in? I believe the hoses themselves are unaffected by something like Barnacle Buster.

As far as antifreeze goes, I know there is a way to test for anti-corrosion additive strength, but if you don't know the age I think a good flush and replace is a good idea. Its cheap and easy and then you KNOW that its fresh, clean and the concentration is correct. BTW - each engine will take almost exactly 5 gallons. There is a drain tap on the port side of each engine just forward of center near the bottom of the block.

Ken

 

[firstbase]

Thanks Smitty. How can I tell when the coolant is need of a change? The coolant in the overflows "looks" good/clean but not sure if that means very much. I thought there was a test that shows how much coolant is left in the system or the quality of it or some such?