Westerbeke W40 overheating under load

[jimbunyard]

Originally Posted by Dylancs

Another update. I used the coolant flush today. It took a long time and a lot of flushing with fresh water to clear the system. This, along with the heat exchanger cleaning seems to have cured the overheating problem. I need to do some more testing tomorrow but I was able to run the engine up to 2500rpm today without issues. So that’s the good news.

Now the potentially bad news. When I started the engine up to run the coolant flush through for the 10 mins required, I noticed a cloudy and somewhat brown looking substance in the water from the exhaust. Almost like some particulate coming out and creating a cloudy substance in the water. It was consistent for the full 10 mins. I assumed it was the residual effects of the barnacle buster and would flush itself out. I had to run the engine a few times while flushing it and the exhaust discharge was the same. It’s possible that this has been happening for a few weeks and I only noticed it now but I can’t be sure.
Just to recap, I put the oil cooler (only the raw water side), heat exchanger and raw water strainer in the barnacle buster bath. When I ran the engine with only clear water, the discharge was the same so I assume it’s not coolant. There isn’t an oily sheen on the water. I’m going to get a sample of the water from the exhaust and the anti syphon valve discharge in a bucket tomorrow. The water from the anti syphon valve is from just prior to the exhaust mixing elbow so I’ll be able to see if there’s a difference between the raw water before and after the exhaust elbow.

Does this sound familiar to anyone? A blown head gasket is what I’m most concerned about but I’m hoping it’s either nothing or something more simple.

Originally Posted by Dylancs

To close this thread, the overheating issue seems to have been solved. It looks like it was the result of previous overheating caused by a blocked 90* fitting where the raw water is injected into the mixing elbow. Judging by how blocked it was, I can only assume it had been restricted for quite some time. I didn’t find it until about a year after I bought the boat. Even though I had changed the coolant several times over the past 3.5 years, it had obviously been contaminated by overheating due to various other issues, such as the incorrect (Westerbeke’s recommendation) plumbing of the water heater and the undersized raw water intake, raw water strainer and exhaust.

The fresh water side of the cooling system became contaminated with a black film as was shown in the article I linked in a previous post. The black film acted as an insulator thereby preventing the exchange of heat.
It’s possible that the engine has suffered some damage over the years from the improperly sized raw water intake (1/2”), strainer (1/2”) and exhaust (1.5”). And also from the previous owner never loading the engine beyond 1800rpm as he claimed. Time will tell. I increased the size of the raw water intake last year to 1”. I’ll be replacing the strainer and exhaust when the parts show up.

Thanks for all the advice and ideas. Hopefully this can help someone else with a similar problem.

Good to hear that your problem may be solved, and that you let us know what happened.

I think the 'brown water stains' are likely a good thing (shows the cleaning was effective) and would only worry about them it they remain after you've run the engine at high rpm for a few hours.

Regarding a potential blown head gasket, I don't recall how high you said the temp got with previous overheating episodes, but if it was less than 210 - 240 F or so, or possibly even a bit higher, you may be 'manufacturing worry'. If the engine starts easily, runs up to rated speed, and doesn't smoke/steam or use fluids, you'll be fine.

Just keep an eye on everything to be sure; as you accumulate some hours your confidence in your repair will build.

Since I'm not too familiar with your specific engine, I'm curious about the 'black film'. Is there anywhere obvious that the freshwater and raw water can be mixed? After running for a while, I'd be tempted to check to make sure that the two systems are totally segregated. I believe, but am not sure, that there is chemical test for salt in coolant.


Hope to hear more good news, and an update after you change the strainer and exhaust...