Westerbeke W40 overheating under load

[Dylancs]

I’ve tried everything I can think of. The details-

1979 Westerbeke W40(Perkins 4-107) 2200 hours in a Niagara 35

Previous owner of 10 years proudly told me he never ran the engine above 1800rpm which he thought was a good idea so the engine has most likely been chronically under loaded for years. Surveyor fell in love with the boat during the survey and decided it was perfect so didn’t check basic things like batteries (all dry and ruined) or engine temp. I discovered the 90* raw water elbow at the exhaust elbow was almost completely blocked which tells me the engine had most likely been overheating for a long time.
Overheating under load above approximately 2000rpm. Temp increases with rpm increase.

Things done/replaced-
Raw water circuit cleaned out. New water pump">raw water pump. Oil cooler, heat exchanger, transmission cooler and v-drive cooler all checked. All new hoses. Exhaust elbow removed and checked for obstructions. Raw water intake increased in size from 1/2” to 1”.
Westerbeke states the exhaust should be 2” all the way back. Mine is 2” from exhaust elbow to muffler then 1.5” from there. The transom fitting is 1.5” and looks original from 1979 so this was the factory installation.

Fresh water circuit-
All hoses replaced.
I discovered this past week that the coolant pressure cap was rated at 4psi and Westerbeke says it should be 15psi. I pressure tested the 4psi cap and it couldn’t hold any pressure. Replaced with a 15psi cap and pressure tested the system. Pressure drops slightly then levels off for hours. Tightened all hose clamps. Tightened the fresh water pump/alternator belt.
Heat exchanger shows a 30F drop in temp between inlet and outlet of coolant circuit.
Water heater installed in system a few years ago. Originally I installed it in series as Westerbeke explicitly says to do. This does not work nor does it make sense. Now it is installed in parallel. Feed is from the coolant alarm sender port on the head which is reduced from 1/2npt to 1/8npt to reduce flow to the water heater and return is to the heat exchanger. There is a shutoff valve in the feed line so I can remove the water heater from the circuit for testing purposes and it doesn’t seem to make any difference.

Air filter was cleaned out. Sea strainer has been cleaned repeatedly. I’m at a complete loss. Nothing I do seems to make any difference. Temperature is being taken at the thermostat (also replaced) with an infrared temp sensor as well as the engine sensor (also replaced).

Sorry for the long post but this has been 3 years of dealing with this and I’m desperate. I’ve been told the cooling system on these engines is marginal to begin with so I’m not expecting perfection. I realize there are many, many reasons for an engine to overheat but I feel like I’ve exhausted most of the possibilities. Any help would be greatly appreciated.

Dylan

[jimbunyard]

Well...the two most obvious candidates are overpropped and/or exhaust restriction. Just because the installation is 'from the factory' doesn't mean it is correct.

[DaleM]

I have a westerbeke 55c that set for years unused that had overheating issues. Some things I did that may help. Clean the heat exchanger, even though it looks good doesn't mean it is good. Clean the transmission cooler, mine was partially blocked that wasn't visible. Check the water flow. Check the actual temp with an ir thermometer, the gage was off. Good luck Dale

[Dylancs]

Exhaust restriction is the next thing I’m going to look at. The stock engine was a smaller Volvo saildrive. The Westerbeke W40 was an upgrade option so I assume they just installed an 1.5” exhaust regardless of the engine. I would need to rig up an exhaust back pressure tester to test this. I’ve already thrown so much money at this issue that I’m hesitant to simply replace the exhaust as the hoses are quite recent and I’ll have to replace the muffler as well.
Being over propped is another thing I’m going to look at. Just trying to eliminate all other possibilities first.

The heat exchanger was boiled out professionally about 2 years ago. I checked it again recently and there were some minor obstructions which I cleared and once again this made no difference. I have run Barnacle Buster through the system for several hours. I have removed all hoses and checked the coolers that I can see through and also blowed through the coolers independently with my mouth to confirm no obstructions. The raw water pump was replaced because the cover was scored as well as the inside of the pump body. Still no difference.
The coolant temp is being confirmed with an infrared sensor. The analogue gauge is converted to digital via an analogue to NMEA2000 interface which has been calibrated to match the thermostat housing temperature. The temperature readings are not erratic and are consistent with rpm increase.

[DougR]

I had the exact same problem and symptoms with a 4-108....
Did all the system checks, pump rebuilds, HE cleanouts, etc.

Finally got rid of the 3” x 9” HE and installed a 3” x 12” HE and the problems disappeared...all systems the same as before. I over propped the engine a bit so it could turn about 3700rpm max and I could cruise all day at 2700 without overheat in 80-82 degree sea water, and push it to 3200 if necessary.

That said, it sounds to me that a temp drop of 30degrees inlet to outlet of the HE should be adequate to cool the engine. Is the thermostat fully opening and allowing full flow?

[roberttigar]

Ditto to DougR. I have had my 33 Morgan for over 30 years. Anytime I got close to 1800 rpm, the temp ran up tp 185. Over 1800 and it got HOT!!!.
So I settled on keeping it at 1800 rpm or less.
Finally about 3 years ago I decided to investigate a solution.
The Standard HE on the 4-108 was too small if the vessel is fitted with a cruising prop.
The solution-either a small prop or a larger HE. Smaller prop didnt make a lot of sense-you would need more rpm's to go the same speed, so I opted for a larger HE.
Sendor makes a 3 x !8"(?) that with minor adjustments works great.
Now I can run it up to 22oo rpm (or more) and the temp stays at 175 always.
Bob

[jimbunyard]

Borh of the last two posts leave me a bit confused, What is the high idle speed of the 4-107 and 8? My understanding has always been that overpropping leads to the inability to achieve rated maximum specified rpm under load, whilst underpropping results in the ability to achieve over the maximum specified rpm under load.(?)

[Lepke]

Many people with 4107 & 8s have installed a larger heat exchanger.
My 1972 - 4108 runs a 14kw generator @ 1800 and never at a full load. I have no chronic under loaded problems.

Since the PO ran at 1800 and the engine overheats above 2000, I'd verify the prop is correct for the rpm you want to run.
Ratings for a 4107 is 3000 rpm max continuous. The 4000 pleasure rating will shorten the life. 1800 wasn't a bad idea.

[DougR]

Originally Posted by jimbunyard

Borh of the last two posts leave me a bit confused, What is the high idle speed of the 4-107 and 8? My understanding has always been that overpropping leads to the inability to achieve rated maximum specified rpm under load, whilst underpropping results in the ability to achieve over the maximum specified rpm under load.(?)

Jim, Your understanding of overpropping is correct....

The max pleasure rating of the 4-108 was 50 hp @4000 rpm.

Perhaps I didn’t take my propping comments far enough...I propped my engine so that at WOT I could only achieve 3700 rpm (slightly over wheeled). I normally cruised at 2700rpm, but could cruise at 3200 if necessary. Anything more than 3200 didn’t achieve an increase in speed because the boat was already at hull speed and anything above 3200 just squatted the stern and made black smoke.

The point that I was trying to make was that even with the engine somewhat over propped, with a proper sized HE installed my 4-108 engine temp was controllable at any engine speed.

[Sailor647]

We have the W46 and have successfully fixed our engine's overheating issue. We didn't notice a problem while in the Pacific Northwest where water temperatures hover around 55 degrees F. However, once we got into Mexican waters that reach 85 F, we had a noticeable problem.

The most significant change we did was to move the oil cooler from the antifreeze side to the raw water side. We placed it after the raw water pump and BEFORE the heat exchanger. This made a huge difference in temperature. We also eliminated the transmission cooler. It is cast aluminum and all it does is corrode in the seawater. Useless. No transmission issues since removing it.

We also moved the original undersized exhaust opening from underwater to the stern. This eliminated a lot of back pressure.

The original air intake "muffler" was removed and a filter installed, which doubled the air intake opening.

We clean (boil it out with muratic acid) the heat exchanger annually and also removed the zinc which just plugs it up faster.

Best of luck.

[Scubaseas]

I tend to agree with DougR and Bob. What is your temp change on the raw water side of the HE? Heat's gotta go someplace.

There's a few calculators on line for HEs if you want to play with the math. A delta 30*F on the FW coolant side sounds kind of borderline to me. https://www.pdhonline.com/courses/m371/m371content.pdf

I would compare the raw water flow rates at both the raw water pump outlet and at the exhaust outlet at the same RPM to determine if your raw water flow rate is good. Also assuming your fresh water side is working OK. If everything is good you either need more HE capacity or less load (like less pitch and/or less engine RPM)

[bad.wabbit]

The coolant side of my cooling system had air trapped in it. Running the engine with the pressure cap off finally got it out.

[Cheechako]

There are two clues here related to that engine:
-The early engines had a smaller heat exchanger and had some overheating issues due to that. Simply not enough heat exchange.
-The previous owner mentioned "he never ran it over 1800 rpm". That's a clue, he didn't run it high because it overheated with the small heat exchanger. It's his way of suggesting you run it low rpm.

My 44 ft boat (avatar) had the 4-108 and later big Bowman heat exchanger. I had it propped for 8 knots at 2400 rpm and it performed flawlessly.

[Dylancs]

Thanks for all the good info. Regarding being over-propped, I can achieve the rated 3000rpm but I’m not certain this is an adequate indication. In fact it’s almost exactly 3000rpm at full throttle. I was told by a local marine diesel mechanic that these engines are known to have marginal heat exchangers, as others have said, so this could definitely be the culprit.
I’ve been thinking for a while now that I was getting air into the coolant system but now that I’ve pressure tested it and tightened all the connections that seems to be eliminated. I have tried running the engine with the coolant cap off but the vibration of the engine simply causes a lot of coolant to slosh out.
The previous owner’s comment about not running the engine above 1800rpm was simply his complete lack of knowledge about boats in general. He initially told me that the engine had “a lot of hours on it, like around 3000”. He then checked and it was 1800. To give some more context, after 10 years of ownership he didn’t know there was a holding tank pump out which was right next to the thru-hulls for the toilet. The benefit of his lack of knowledge was that he had professionals do all the work required. Unfortunately it also meant he never bothered to check engine parameters. Had the surveyor done his job properly and had I been looking as well, we would have seen the engine was overheating under load during the sea trial and this could have been resolved during the purchase 3 years ago. Live and learn.

My oil cooler is already directly after the raw water pump. The circuit is- 1” intake, Groco raw water strainer, 3/4” hose to raw water pump, 5/8” hose to oil cooler, 5/8” to HE, 3/4” to transmission cooler, 3/4” to V-Drive cooler, 3/4” to anti syphon, 3/4” to exhaust elbow.

I’ll add a photo of the engine later today when I’m at the boat in case there are any obvious visual clues that I’m missing.

[onestepcsy37]

i had an overheating problem on my perkins 4-108, the only problem i had with it in the ten years i owned the old engine.


tore the cooling system apart and found nothing. nothing. on a whim, i removed the generator/fresh water pump drive belt. i spun the pulley on the fresh water pump. it spun freely. shoudln't spin freely - theres an impellor and water on the other side.


removed the fresh water pump - four bolts - and sure enough the pulley and the impellor were no longer solidly connected. took it to marsh harbor marina and the mechanic there, who was a factory trained perkins mechanic, said he hadn't seen that happen ever in his many years on perkins engines.