Steaming again...

Hi! A few months ago, I had posted here my saga of my MD2030's white smoke issue, which was largely resolved by servicing my injectors and a water restriction. Well, I am now seeing some steam (not smoke) and elevated engine temperatures. Nothing is odd suggesting a head gasket issue--oil looks great, and the engine holds pressure just fine. The through-hull and fittings are clear, and I've checked for collapsed hoses. The impeller was just replaced and the heat exchanger is also new.

Raw water flows from the seacock to a Perko strainer and then goes through the transmission and up to the impeller. After my last trip, I felt the transmission, and it was hot to the touch; the impeller cover was also very warm to the touch. Gulf temp was 85 degrees, and the exhaust water was very hot.

There "seems" to be enough water exiting the exhaust, but I am wondering if there is a blockage/obstruction at or inside the transmission. The engine/gearbox is 12 years old and has never been "barnacle buster" since I have owned her since 2012 or so. I am going to treat the engine and see what happens!

A combination of elevated temperatures and steam definitely sounds like a flow restriction on the raw water side. When you replaced the impeller, did you check for any stray impeller pieces that may have gotten stuck in something down-stream of the pump?

rslifkin said:

A combination of elevated temperatures and steam definitely sounds like a flow restriction on the raw water side. When you replaced the impeller, did you check for any stray impeller pieces that may have gotten stuck in something down-stream of the pump?

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Thanks. Yes, the impeller is new and I replaced the heat exchanger a few months ago with a brand new Volvo Penta (cost an arm and a leg). The boots were installed carefully and I do not have coolant overflowing suggesting that sea water is not getting in the fresh water side. I've never lost an impeller blade and didn't find any when I replaced the exchanger.

The exhaust riser is "fairly new" (2016 I recall) and I recently opened the various inspection ports to chisel out some carbon--nothing major. I do reach WOT just fine.

Could it be a thermostat sticking? I just reread your post . I don’t think it’s thermostat. A while back my strainer was not sealing off completely and I was getting air bubbles in stainer. I fixed that and also reworked my raw water pump, with new cam, impeller, o ring and new end plate .
The temperatures have improved some but I think I still have a sticking thermostat.

Pack Mule said:

Could it be a thermostat sticking? I just reread your post . I don’t think it’s thermostat. A while back my strainer was not sealing off completely and I was getting air bubbles in stainer. I fixed that and also reworked my raw water pump, with new cam, impeller, o ring and new end plate .
The temperatures have improved some, but I think I still have a sticking thermostat.

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Hi, Pack. I hope you get your challenge fixed as well. I replaced my thermostat about three years ago with the correct VP part. It was a pain to replace as one must pull the water pump. I went ahead and replaced the water pump while I was there. The raw water pump was replaced around the same time as it was beginning to leak.

Interestingly, the problem coincided with me removing the coolant fed cabin heater and plugging the ports at the engine. The heater must have been dropping the engine temp enough to mask another problem.

I should also add that my engine through-hull is 1/2" NPT with a 3/4" FF barb. To increase water flow, I used a Y splitter to tap into an adjacent through-hull for the A/C. It appeared to help but delayed the steam problem.

Again, it all seems to coincide with the heater removal; I never had this issue before.

I ordered two gallons of Barnacle Buster and will clean out the system this weekend.

I have offered my tome below about steaming.
It may not cover everything but it does cover a lot of the sources of steaming.
If there are specific questions later then ask and hopefully they can be answered adequately.

As for the transmission does the unit have a built in cooler or rather does it have an exterior to the gearbox mounted cooler like most drives?

They can become plugged which will cause the gearbox to run hotter, yes, but that can also restrict seawater to the engine cooling.

Just because you worked on lt months ago doesn’t rule out broken impeller, impeller blade or barnacles regrowing in the system.

When I worked on boats, I fixed many overheat problems others couldn't solve by doing a proper flush of the fresh water side. Often the people before me had installed new pumps, heat exchangers and exhaust elbows and never solved the problem.
Also the anti-rust additives in coolant solutions only lasts so long. Eventually you get a flak rust buildup on the water jackets and in the head water passages. The rust doesn't transfer heat well and you go from normal operation temps to too hot quickly.

C lectric said:

I have offered my tome below about steaming.
It may not cover everything but it does cover a lot of the sources of steaming.
If there are specific questions later then ask and hopefully they can be answered adequately.

As for the transmission does the unit have a built in cooler or rather does it have an exterior to the gearbox mounted cooler like most drives?

They can become plugged which will cause the gearbox to run hotter, yes, but that can also restrict seawater to the engine cooling.

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I appreciate the document--very helpful. The transmission cooler is built in. There are two coolant pipes on either side for raw water flow. One coolant pipe is new, but I have not inspected the other. Perhaps a blockage at the cooler. The new impeller was installed Saturday before my trip, and there were no broken fins on the old impeller.

I will report the outcome of my Barnacle Buster treatment. I will also double-check the exhaust elbow inspection ports and run the end of a coat hanger through them. Given the transmission seemed unusually hot and the impeller cover was very warm, I am hoping the issue is a blockage at the transmission cooler.

I will provide a report this weekend!

Did you actually block the outlet/inlet that leads to the water heater or did you loop them together? If you blocked, you may have restricted some coolant flow. Suggest you try a short piece of hose and loop them together if that was the case.

Here are a couple of things to consider as well:


Mud/sand in your heat exchanger. If you have operated in shallow water or run your boat at the slip in shallower water, it is easy to stir up the bottom and have it get sucked into the raw water intake. My boat had this when I bought it. I took the end caps off the heat exchanger and shown a strong light through the core tubes. I was shocked to see 20% of the tubes were blocked.


Barnacle growth in your seacock. I had this happen this season. Removed the intake hose at the valve and opened the valve. Water came out but did not gush. I ramrodded the seacock with a wood dowel. I felt the barnacle break off and water came gushing in. Reassemble and enjoy.


Did you burp your cooling system (purge any air out) after working on the waterpump, etc? This can cause your engine to run warmer than designed.



Just thoughts worth looking in to.

ronlord said:

Did you actually block the outlet/inlet that leads to the water heater or did you loop them together? If you blocked, you may have restricted some coolant flow. Suggest you try a short piece of hose and loop them together if that was the case.

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Hmmm.... interesting. Yes, I used plugs supplied by Volvo. I kept the hose barbs and could create a loop as you suggested.

SeaBreeze said:

Here are a couple of things to consider as well:


Mud/sand in your heat exchanger. If you have operated in shallow water or run your boat at the slip in shallower water, it is easy to stir up the bottom and have it get sucked into the raw water intake. My boat had this when I bought it. I took the end caps off the heat exchanger and shown a strong light through the core tubes. I was shocked to see 20% of the tubes were blocked.

Barnacle growth in your seacock. I had this happen this season. Removed the intake hose at the valve and opened the valve. Water came out but did not gush. I ramrodded the seacock with a wood dowel. I felt the barnacle break off and water came gushing in. Reassemble and enjoy.

Did you burp your cooling system (purge any air out) after working on the waterpump, etc? This can cause your engine to run warmer than designed.

Just thoughts worth looking in to.

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Thanks. I checked the seacock and used a small screw driver to clear out a possible blockage. It appeared clear and I had water gushing out. I once had a barnacle growing inside the hose barb on my strainer, which led to an overheating issue. On a related note, I have an annoying scoop strainer that can be a problem keeping clean and clear. My plan is to eventually remove the scoop strainer and replace with a traditional through hull.

I will double check the exchanger as well!

My gearbox cooler is external but still in the raw water circuit. When I thought I had a different problem I pulled the gear cooler off and found the bottom tubes were blocked, about 20% of the tubes.
I cleaned the whole thing , reassembled and pressure tested and it has been fine since.
I did not see any sign of overheating in the engine but since it is integral in the circuit it would have caused trouble at some point.

Lepke's comment about a flush are valid also. I did mine many years ago and maybe it's time again.

Your problem may still be the raw water pump. End plates wear reducing water flow. The bore wears and may be allowing water to by pass the impeller blades. The compression fork may be worn to the point where the flow diminishes.

How many hours are on the water pump from new?

Ted

Wow, a lot of good suggestions. Being a Great Lakes cruiser I don't have to deal with barnacles and rust and corrosion are not as big of a deal as you "salties" deal with every day.

But.. one thing really caught my eye ! A half inch through hull to supply cooling water to the engine ? I think mine is a 2 inch hose to the strainer then about an inch or inch and a half to the fresh water pump.

Also my exhaust water is barely warm. My engine runs at 180 degrees but the volume of fresh water through the system is massive, it exhausts cool enough to easily put your hand into the stream.

Just a little restriction could cause the issue of steam.

pete

O C Diver said:

Your problem may still be the raw water pump. End plates wear reducing water flow. The bore wears and may be allowing water to by pass the impeller blades. The compression fork may be worn to the point where the flow diminishes.

How many hours are on the water pump from new?

Ted

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Hi, OC. The pump has about 75 hours on it since I replaced it. The old pump was definitely leaking. I didn't have any temp issues before replacing it--just water going in the bilge!

Pete Meisinger said:

Wow, a lot of good suggestions. Being a Great Lakes cruiser I don't have to deal with barnacles and rust and corrosion are not as big of a deal as you "salties" deal with every day.

But.. one thing really caught my eye ! A half inch through hull to supply cooling water to the engine ? I think mine is a 2 inch hose to the strainer then about an inch or inch and a half to the fresh water pump.

Also my exhaust water is barely warm. My engine runs at 180 degrees but the volume of fresh water through the system is massive, it exhausts cool enough to easily put your hand into the stream.

Just a little restriction could cause the issue of steam.

pete

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This is indeed a great source of information, and I will be following through on the advice given here. The MD2030 uses 3/4" hose. After the PO repowered the boat in 2006/7 from an 18HP Perkins, he kept the original 1/2" through-hull and replaced the barb with a 3/4" full flow. Over the weekend, I tapped into another through-hull for the A/C using a Y connector. Interestingly though, I didn't have the steam issue when I originally bought the boat. It all seems to go back when I removed the coolant fed cabin heater.

I am putting my money on a restriction at the transmission cooler but will be checking the other stuff as advised by TF members. I hope to share a positive report this weekend!

Lots of good advice here. I'm curious about the actual 'elevated temperature' - is it above spec? That's a small motor to be supplying a heater - maybe it ran cold until you removed the heater loop and is now operating at its design temp. I think you're right in flagging the removal of the heater as a contributing factor in higher operating temps, but if the motor is not overheating you may not have a problem.

To all the very good advice you've received, I would like to add that a restriction or anything that causes low total flow *anywhere* in the system, from the intake through-hull to the mixing elbow can cause overtemp issues. If you don't move enough water through, you won't get the cooling you need.


I didn't see you mention the mixing elbow. If that is clogged with scale or corrosion it can greatly impede the water flow.


Ken

Jeff F and Kchace,

Yes, I had suspected the engine was running too cold with the heater. It seemed to take way too long to reach operating temperature. The cabin heater was rather large, and I had no use for it in Florida (freed up some space under the galley).

Normal operating temperature for the engine should be between 167 and 194 per the manual. If I push the engine beyond 2700 RPM (WOT is 3600), she reaches 200 degrees in a few minutes and produces steam out the exhaust. I believe the alarm sounds at 205, but I throttle back before then. Before the steam/temp issue and removal of the cabin heater, I used to run the boat at 2700 as my cruise and had no problem running her at WOT.

The exhaust elbow is just a few years old, and I removed some carbon via the elbow's various inspection ports with a screw driver a few months ago. I am going to reinspect and run a coat hanger through the ports to be certain.

My theory is the cabin heater was keeping the temp down and "masking" another issue. The very warm impeller cover and hot transmission suggest to me a blockage exists in the interior transmission cooler. It has never been cleaned to my knowledge.

Thank you everyone for your help! I will know more this weekend!

It sounds like you're on the trail.... Don't forget to check the injection point on the exhaust elbow. The point where the water hose connects to the exhaust elbow. Sometimes those fittings get corroded and scaled to the point they can limit the flow of water.


Ken

I tend to go with the small suction leak downstream of the seawater pump. The heater in the circuit could have been masking a borderline situation. The heater ports can just be plugged.

An easy, and for saltwater cooling systems, a regular necessity is to descale/clean the system with Rydlime or Barnacle Buster. It is far easier than removing the system components when no other reason exists to pull them. I won't belabor the point with an unnecessary description of the process, but I find it exceedingly easy for both main engine and my generator. You could see an immediate cessation of the steaming.

One point about steaming that last weekend cruise reminded me. Outside temperature is a great factor.
As an example, last Saturday was 2C outside, water temp around 14C. My water exhaust is somewhere around 35C, not very hot, you can put your hand in and it feel warm not hot. However with a 2C air temp steam is obvious, even the river water itself was steaming.

L

rgano said:

An easy, and for saltwater cooling systems, a regular necessity is to descale/clean the system with Rydlime or Barnacle Buster. It is far easier than removing the system components when no other reason exists to pull them. I won't belabor the point with an unnecessary description of the process, but I find it exceedingly easy for both main engine and my generator. You could see an immediate cessation of the steaming.

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I was unable to make it to the boat last weekend for the Barnacle Buster flush, but this Saturday is the day! I hope my hunch is correct and the issue is a restriction in the transmission cooler.

Vashon_Trawler said:

I was unable to make it to the boat last weekend for the Barnacle Buster flush, but this Saturday is the day! I hope my hunch is correct and the issue is a restriction in the transmission cooler.

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I hope that works, but playing devil's advocate here. You mention that your transmission gets seawater first. Maybe there's fine sediment in the coolers that has setteled out, hardened, and causing the problem. I've seen this on some of the boats around here. Maybe I'm misunderstanding where your transmission cooler is in the raw water loop.

ben2go said:

I hope that works, but playing devil's advocate here. You mention that your transmission gets seawater first. Maybe there's fine sediment in the coolers that has settled out, hardened, and causing the problem. I've seen this on some of the boats around here. Maybe I'm misunderstanding where your transmission cooler is in the raw water loop.

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Good point. The transmission cooler is inside the transmission and after the sea strainer but before the raw water pump. There are two coolant pipes on either side of the transmission, which attach to hose. I replaced one due to a leaky seal but the other is original. Perhaps the blockage is in the other pipe or in between. I will pull off the original coolant pipe after the flush and inspect.

Good luck on it and we hope to hear of your great success.

Results are "partially" in... Thanks again for all the advice. For those that followed this post, I had suspected my transmission cooler was clogged. The heat exchanger was clear and I checked for blockages at the the through hulls, hoses, and fittings--all good. I installed a new impeller and looked for collapsed hoses (all are new) and kinks. I also opened up the mixer elbow and, despite a little carbon, it was not blocked. I did chisel away some carbon via the inspection ports. Everything was fine.

I ran two gallons of barnacle buster through the intake and let it "soak" for 12 hours. Unfortunately, it was late when I started the engine up and was unable to take her out; however, I was somewhat pleased with what I saw leaving the exhaust. It was dark, but with a light I could see some chunks of carbon and a large white cloud... dissolved calcium and salt? I put the boat in gear while tied and could definitely "feel" and see a difference with the force and volume of the water leaving the exhaust. She emptied a 2-1/2 gallon bucket of water in a minute at idle (800 RPM). After 10+ minutes of running the engine both in idle and gear, the exhaust water and impeller cover were cool.

I will take her out next weekend and report. We'll see how she handles WOT!