Diesel engine temperature issues

[Blake Payette "Procyon" N33 Vancouver BC]

Good morning: I have a Universal model 5432 in my 33. When cruising under power  (2000 rpm) the temperature never goes above 130-135 F. The book says that the temperature specification is 165-185.  

 I am in the process of replacing all the coolant hoses (all original from 1989) and I pulled and checked the thermostat. The thermostat starts opening at 165 and is fully open at 185. (functioning normally) I have checked the engine temperature with a IR thermometer and it verifies the indicated gauge temperature.

Any ideas what might be the cause of the overcooling? Is this an issue that I should be concerned about?  The engine seems to run fine otherwise.

Blake Payette

Procyon

N33 Brentwood Bay BC

[Ward Woodruff]

Put it back together with a new thermostat.  It can’t hurt and might help. 

Ward Woodruff

N33 #8 Margery

Niantic Bay, CT

On Jun 2, 2025, at 12:29 PM, Blake Payette "Procyon" N33 Vancouver BC <procyo...@gmail.com> wrote:

Good morning: I have a Universal model 5432 in my 33. When cruising under power  (2000 rpm) the temperature never goes above 130-135 F. The book says that the temperature specification is 165-185.  

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[Joe Valinoti]

Most interesting.  My first guess would have been the thermostat you have checked it.  Maybe too much water circulating??  I would not ignore this as that engine is designed to run at 160 to 180 and running too cool is not good for it.

 

Joe Valinoti
S/V iL Gatto NS30U #221
Sea Harbour YC
Oriental, NC USA

~~~~~(\_ ~(\_ ~(\_~~~~~~~~~~

[Mark Powers La Reina 26C Vancouver, B.C.]

Blake, what happens if you run at 2200 rpm? One possibility is that the boat is under propped and not working hard enough to come up to temperature. Are you getting to hull speed at 2800 rpm? 

Mark Powers

[Blake Payette "Procyon" N33 Vancouver BC]

Actually I haven't tried that or thought of that as an answer. Once everything is back together I will give that a try. I usually cruise at 2000 rpm (6 kts) . The engine seems happy there.

[newelljc9]

My 1981 Universal 16 ran cool when I bought Mascouche in 2006. The problem was that she was equipped with a small two bladed folder designed for a high revving gas engine. That winter I contacted Ben Hawke and on his advice installed one of his three bladed Slipstream folders. He nailed the perfect diameter and pitch so the engine peaked at its maximum rpm 0f 2,800. Ever since then the engine has operated at the correct temperature and Mascouche gained a knot in cruising speed. The Universal did not seem to suffer from not reaching its correct temperature range for 25 years. It seems to be as good as new, perhaps because the Pangmans loved sailing and seldom resorted to using the engine which when run flat out could only reach 4 knots in favourable conditions.

I am still impressed that Ben matched the prop with a 25 year old engine perfectly. Good for the Australians. I could not afford a European folder at the time while the Canadian dollar was in the tank.

John Newell

Mascouche 26C 1

Toronto 

[Bill Barr]

I confess that I'm a bit mystified by all this.  My 26U, Garuda, is equipped with the standard Universal 3cyl and has a 2-bladed propeller.  Her operating engine temperature also rarely rises above 140 degrees.  Granted, if I maxed out the rpms, the temp may rise but I almost never run above 1800 rpm because at that rpm she reaches 5 to 6 knots, which I reckon is about maximum hull speed and  pushing higher would reduce efficiency. 

Bill

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[Rick Merullo]

Could it be the temperature sensor or the gauge?

Rick Merullo

NSU 471

Moonbeam 

Manchester MA

~ ~ ~ ~  (\_ ~ (\_ ~ (\_~ ~ ~ ~ ~  (\_ ~ (\_ ~ (\_~ ~ ~ ~ 

 

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[Sprio]

Is there a water heater (calorifier) connected to your engine? I ask because most diesel engine blocks used in marine applications have a dedicated heater hose connection — a coolant loop that bypasses the thermostat.

However, some engines lack this feature, like my frustrating Westerbeke W52. In such cases, various workarounds are often implemented to get the water heater to function properly, but these can have significant consequences for the engine’s operating temperature, which is normally regulated by the thermostat.

mark h

n36#25 netherlands

Op woensdag 4 juni 2025 om 04:52:22 UTC+2 schreef Rick Merullo:

[Barry Connell]

This winter I replaced my tired W52 with a Yanmar 57, which is more powerful, more compac,t and will be more reliable. At the end of this season I can tell you how the hot water worked. 

Barry Connell

W36 Nocturne

Newburyport, MA 

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[Sprio]

I thought it was fitting to chime in on this thread, as my engine driven tap water heater is causing similar issues: an engine running too cold. The W52 annoys me on a daily basis — I honestly think it's a poorly marinized version of what was otherwise a very decent base engine (Mazda).

That said, I’m also planning to replace the W52, but only once it really starts acting up (smoke, leaks, hard starting, or rough running). For now, it runs just fine — frustratingly fine, even.

Hopefully, by the time my W52 kicks the bucket, electric propulsion technology will have matured to the point where choosing between diesel and electric is a no-brainer.

I have to say, it's noble of you to rename the N36 to W36 — a fitting tribute to an engine that, in my opinion, should never have been designed in the first place.

mark h
n36#25 (not W36...) netherlands

Op woensdag 4 juni 2025 om 15:48:50 UTC+2 schreef Barry Connell:

[S/v PELICAN]

Just spent two days motoring up the Chesapeake Bay against rough seas and strong north winds at rpm ranging from 1700-2600.  My old (5700 hrs) Universal M35 temp stayed at 160 continuously.  I have a very reliable Excel propane water heater so no issues with hot water tank and plumbing.

I’d be looking at the gauge and temp sensor after all else failed.  Perhaps a simple wiring issue on the back side of the engine control panel.  They get pretty tired looking after so many years of unrecognized faithful service.

Ed Strazzini

PELICAN, N33#36

Deltaville, VA

Sent from my iPad

On Jun 4, 2025, at 12:17, 'Sprio' via INA Nonsuch Discussion Group <INA-Nonsuch-Di...@googlegroups.com> wrote:

I thought it was fitting to chime in on this thread, as my engine driven tap water heater is causing similar issues: an engine running too cold. The W52 annoys me on a daily basis — I honestly think it's a poorly marinized version of what was otherwise a very decent base engine (Mazda).

To view this discussion visit https://groups.google.com/d/msgid/INA-Nonsuch-Discussion-Group/b57bf099-3c1c-4346-8fe0-a7dc561a1edbn%40googlegroups.com.

[Blake Payette "Procyon" N33 Vancouver BC]

The temperature gauge reads the same as when I check the temp at the thermostat housing with a IR thermometer so the gauge and the temp sender are good.  I have installed a 180 thermostat and finally managed to bleed the cooling system. We are taking the boat out this morning and we will see how things work under load.

[Blake Payette "Procyon" N33 Vancouver BC]

update on temperature issues: After replacing all hoses and clamps in the cooling system and having the heat exchanger professionally cleaned and pressure tested and installing a 180 thermostat the system now cools very well and runs at a steady 180. I never did find out why it ran at 130 before, no problems were found and the installed thermostat tested good. 

I guess that the thermostat is a cheap thing to replace.

[Joe Valinoti]

Consider it a learning experience, Blake, as I’m sure you’ll never forget it..

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[Sprio]

That's actually a good outcome—so good, in fact, that it makes me question my own issue with the Westerbeke w52 temperature. I added a water heater without really knowing what the situation was like before. I also tested the thermostat in a pot, just Blake you did. It’s entirely possible that simply replacing my thermostat might fix the issue, even though it seems to behave fine when I check it with a thermometer while cooking.

Maybe I should just take the advice of someone like Joe, who knows what he’s doing—would definitely save me a lot of time figuring everything out myself.

mark h
n36#25 netherlands

Op zondag 8 juni 2025 om 17:22:14 UTC+2 schreef Joe Valinoti: