Strange Westerbeake overheating problem

[Capt. Mike]

My westerbeake 30 (4 cylendar) engine has been running a little too hot for some time. The boat is not used very often. Recently I decided to bring the boat from the Bahamas to Florida, but during a load test with the boat tied in the slip and running in gear at 1700 rpm the temp went to nearly 200 deg F in less than 10 minutes. A previous owner removed the thermostat. I spent several days troubleshooting and at the end of that time I realized that if I have fresh water or a borax flush solution in the closed cooling side with no anti freeze, the engine runs under load at 1800 rpm for more than an hour with the temperature stablizing at under 180 deg F. If I use anti freeze in the fresh water side, the engine temperature runs away in less than 10 minutes.

I have: cleaned the raw water side of the heat exchanger with a muriatic acid solution; used a meat thermometer to verify accuracy of temp gauge; back flushed the fresh water side with a garden hose; inspected the raw water pump impeller; pressurized the fresh water side and found no leaks; ran the engine with a borax flush solution in the fresh water side for an hour each time for five times; removed and inspected the fresh water pump.

A friend who is a salvor in the Bahamas explained the situation by saying that anti freeze does not transfer heat as well as water and that with the thermostat missing the anti freeze circulates fast enough that it simply does not have time to transfer heat as it passes quickly through the heat exchanger.

Any comments?????

Mike

[redtech]

your friend is right without the thermostat so slow and control water/coolant flow in the block it will not transfer heat propperly. if you don't have it install one. something else is the water pump impeller may look good but how about the housing and wear plate an ok impeller and scored housing can get you hot too

[Capt. Mike]

Thanks for the reply. The raw water pump was new 2 years ago with little use since then. When I removed the plate to inspect the impeller, I looked at the plate and there was no scoring. How do you feel about running with water and no coolant on the fresh water side? If the engine temp is 180 deg F, what should the temperature of the exhaust water be?

Mike

[redtech]

anti-freeze provides more than just protection from freezing like protection of the metals inside the engine and rises the boilling point of the coolant. so not a big fan of staight water. exhaust should be warm to hot to the touch but not burning about 135-170 at the riser. if hotter you may have a restriction

[alan white]

All things being equal, the fresh water pump will pump slightly more water than antifreeze because antifreeze is heavier (higher specific gravity).
I've always seen engines without thermostats run cooler, not hotter, but I think Redtech knows more than me about exchangers (my experience is with radiators). I'd suspect the raw water side as it is more prone to corrosion than the cleaner fresh side. The raw water pump you installed---- was it the same as original, same pulley, same dimension impeller? It may be that it is undersized.

Alan

[Capt. Mike]

Yes. The new raw water pump is an exact match for the old one. It came without a pulley and I moved the pulley from old to new. I have not cleaned out the raw water path in the transmission cooler and the oil cooler. I have not checked for an obstruction in the water/exhaust mix tube. I'll do those things when I get back to the Bahamas. I bought an ir thermometer. What should the temperature of the exhaust water be, if the engine temp is 180 deg F?

[alan white]

I don't know, but you did good buying the IR meter. Point and it's like magic. If you can possibly find another engine in someone's boat and make some spot temperature comparisons, you might learn something.
Especially note the volume of water exiting with the exhaust. At the same RPM, it should be the same volume. Also, I was wondering about the engine's temp sender. I am assuming it would read the same for water or antifreeze, but it operates by grounding through the coolant. Hot coolant conducts more easily, hence the more current going through the guage. Maybe plain water always conducts less than an antifreeze mix. Dunno. spose you could check with a cup of each and an ohm meter. Any case, the new instrument you bought should show a difference if there is one.

[MMNet SEA]

Originally Posted by redtech

your friend is right without the thermostat so slow and control water/coolant flow in the block it will not transfer heat propperly. if you don't have it install one. something else is the water pump impeller may look good but how about the housing and wear plate an ok impeller and scored housing can get you hot too

Red Tech's question was very relevant in terms of the use of the raw water pump and it's impeller.

I have noted that if a pump is not used for a long time the salts in the impeller chamber concentrate and when finally the engine is used again the impeller is either damaged or deformed, the salts also damaging the rubber in the bearing seal.

[Capt. Mike]

The engine had been idle for about two months. I will replace the impeller when I get back to the Bahamas. The exhaust water did seem to be a good flow though and did get better after I cleaned the raw water side of the heat exchanger. Also I noted that when the engine overheated, the exhaust water did not feel as hot to the touch as when the engine did not overheat. From that I surmised that the raw water side was operating properly and that the problem is on the fresh water side. Again though an impeller is a small cost for the comfortable feeling that I tried that too.

Thanks,
Mike

[kenJ]

I too was having overheating problems, tried all the flushing/cleaning you have mentioned, but the problem seemed to get worse after the cleaning. In frustration I removed the heat exchanger intending to manually clean the interior. When I popped the end cap I found pieces of approximately 5 impeller blades retarding the flow of cooling water that previous owners didn't remove. I think all the cleaning I did moved some of the peices from the hose to the heat exhanger causing the blockage.

[Capt. Mike]

Thanks Ken, I had the end cap off early in the trouble shooting process to be sure it was seated correctly, but that was before all the flushing. I'll remove and inspect again.

Mike

[kenJ]

Not sure if this applies to your engine or not. On some Westerbekes there is a mixing elbow where the cooling water is added to the exhaust. They are very prone to getting plugged up with corrosion and mineral build up. A restriction there will slow the flow of cooling water. Most people just replace them rather than trying to clean, don't think they are that expensive.

[Capt. Mike]

Someone else mentioned the same thing. I won't be able to get a replacement in the Bahamas, but when I get back I plan to remove the hose and fish around inside the elbow with a coat hanger after just blowing into it to see if it seems constricted. Thanks.

[charmc]

The heat transfer coefficient of a 50% glycol solution is about 0.87 -0.90 that of plain water, so that should account for the 10% difference in temp that you saw when testing with just water. Most engines are designed to run with a glycol solution on the fresh water side, however, so I'd agree you're running a little hot. The suggestions others have made for areas to probe for junk that could restrict water flow are all good. One other thing to consider is cleaning the raw side of the exchanger with a caustic solution. The acid you used is perfect for dissolving/loosening mineral deposits, like calcium, even barnacle shells. Organic matter, like "seaweed" or minute organisms that may have gotten past a strainer, is resistant to acid cleaning, however. Caustic cleaning is required to remove this type of material.

Overall, it sounds like the previous owner didn't keep up with cooling system PM, and you're left with a few chores to do to get it back to spec. Have fun!

[Capt. Mike]

That's an interesting idea that may have merit too. What basic compound would you suggest. Would something like baking soda be enough or something more harsh?