operating temp yanmar 4jh4 hte 110 hp

[jimbeam]

I have a 13 year old ranger tug 25 with a yanmar 4jh4 hte engine. I'm wondering at what temperature the engine should be running at doing about 2800 rpm.
It sems to climb to around 195 F doing around 2500 to 2800 rpm. As soon as I slow it down to about 2200 rpm the temp drops to 175F. Is this normal? Seems to me it should not change hardly at all at 2800 rpm. I have changed the antifreeze (prestone dex cool) and 2 years ago changed the thermostat. Yanmar stated that they changed the impeller to a slightly stronger one for higher rpm's. I wonder if that is the cause.
jimbeam

[GreenWave]

I dont have the exact same yanmar. Mine is the 75 hp 4j3 HTE. At cruise of 2000 rpm I run around 180-185. If I go above 2800 then she gets to that 195 mark. Have been told this is normal expected operation.

[StuM]

Are your numbers from a temperature guage or are they measured witha temperature gun? (I've seen gauges that differ by 5°F or more from what a gun says)



I haven't looked at the operating temperatures on that specific Yanmar, but in my experience, those numbers are pretty much standard for small/medium Yanmars with a heat exchanger.



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[Dockhead]

My 4JH3 HTE runs exactly 80C in any operating condition. If I see even 81C, then I know that there is seaweed in the strainer.


To have proper cooling, you need:


1. Clean strainer
2. Intact impeller
3. Unclogged heat exchanger
4. Unclogged exhaust elbow (which otherwise can block the flow of seawater)


I would work that through if I were you. The heat exchangers can build up calcium deposits and sometimes need to be rodded out. As an example of one possible source of cooling problems.

[Russ]

I gave this engine and have run it for 12 years at 2700 rom cruise it usually runs at a steady 185-190. Recently it started to overheat and slowing down dropped the temp to 175. Fir what it’s worth your temp alarm goes off at 205F. I am researching my problem as we speak Agreed re impeller seawater strainer etc. I just cleaned my condenser and replaced antifreeze so it isn’t those.

[teacherm]

I have the same symptoms and would appreciate keeping the thread open. I have changed my antifreeze and thermostat ,checked exhaust elbow and strainers replaced impeller with no change. My next action will be to clean out the heat exchange tubes with a wire brush tiped rod.

I will update the post with my results in about a week..

[Ericson38]

I'm doing this on our 4JH2-HTE. To get the rear cap off the heat exchanger, you are going to have to remove the turbo. Which meant removing the intercooler and intake ducts before getting the turbo off. At least I did.

[Russ]

You can clean the intercooler in place using Barnacle Buster it IS Yamnar improved and works excellently. I cleaned mine but then had to remove the turbo so I got to look into the intercooler spotless!
Also It is simple to do. Send me a PM if you need help.
svascension@yahoo.com

[Kd9truck]

I took a Yanmar owners class from Mack Boring a Yanmar dealer in NJ 2 years ago these are my notes from them on cooling systems.

cooling Systems:
Change coolent,change thermostat .
Anti freeze is a Closed loop.

Engine should be at 185° when at temp running, even at 200° will shorten the life.

Anti freeze is air cooled, in my boat, it goes to the hot water heater as well.
boat may also have a hot water heating element.
Yanmar Manuel calls the coolant fresh water
anti freeze does not lose its strength with water 50/50 is the ratio. If there is rust you must swap out.

YG30 is yanmar product- change every 2 years.

YG30 is Yanmars coolant it is formulated to compensate for the lack of Zincs on the motor, it should be changed every 2 years. I get it from Amazon, I don’t fight the proprietary coolant issue it’s not worth it to me.

I have an exhaust fan that runs when the power to the motor is turned on, there is 4 inch supply and make up vent hose I believe this is a big part of the motor maintaining temp at different RPMs
Cheers