3gm30f water temp hot

[Pete]

I am having a problem with the engine water temp running hot. I checked the sea water side of the cooling system including the sea water pump impeller,mixing elbow, the heat exchanger core and made sure there are not blockage in the water line and strainer.The water flow seams good. On the closed cooling system I changed the thermostat, new antifreeze and blead the air. The engine temp runs 185 to 195 when motoring at 2800 rpm or more. Takes less then five minutes to get that hot. I even took the new thermstat out and still have a overheating problem.Don't think it is the gauge as the heat exhanger is very hot and gauge seams to read low when engine is cool and warming up.With the thermostat in the water temp was 175 to 180 at the dock with engine at 2500 rpm.I checked the engine water pump and that seams to be working. This is a new problem as the engine alway ran 160 to 165 before not matter what.This is a 3GM30F Yanmar(1996) with appx 350 hours on it. I know I am missing something but I can't figure it out! Any body have any ideas? Thanks !!

 

[Al Miegel]

Check the exhaust elbow for restriction.

Check to make sure the exhaust elbow, where the raw water enters the exhaust is not glogged. Also called the exhaust riser. Single most frequent cause for overheating. Also buy or borrow a infrared temperature guage to confirm that you're not over heating and to help locate where the bolckage is.

 

[Tom]

Mix Ratio

Verify the mix ratio of the antifreeze/coolant.50/50 should be the coorect mix.

 

[James Marohn]

Mixing Elbow

I too had similar problem. Never motored above 2200 to keep cool.Read somewhere that the mixing elbow (big hunk of U-shaped metal) is rated for 6 years on 6 hours a day usage. What a pain to replace, but once I did I'm back up to 2900.Cheers,-j-

 

[Steve Dion]

Did you remove the elbow?

Pete:Did you actually remove the mixing elbow to inspect it?There has also been problems with impellers, you may want to pull it and check it again too. The inner part sometimes seperates from the rubber portion of the unit.Check all of your hoses to see if they are collapsing when you rev up the engine. Have you run it at the dock in gear and see if there is any difference?

 

[Don Alexander]

Netting round the Prop?

Any increase in the resistance of the prop to rotation causes the engine to work harder and can easily overheat the engine.Also are you quite sure the raw water inlet thru hull is not partially blocked?