Overheating Volvo Penta

[Gator]

I'm going nuts. I have a Beneteau Oceanis 390 with a Volvo Penta 2003T 3 banger diesel with serious overheating issues. I can't run her more than 20 minutes before she overheats.

I'm on my 3rd mechanic, not counting myself.

The heat exchanger and the oil cooler have both been overhauled. The water pump">raw water pump has been rebuilt and the raw water flows great. Every hose has been replaced. This includes the intake hoses to make sure they have the wire coils to keep them from collapsing given the suction.

Today I took off the circulation pump (fresh water) hoping it was the problem. The impeller looked brand new. My mechanic has a great reputation in the area, he has put in at least one work's solid work (if not more) on the engine...and he's frustrated. He brought in a second mechanic who did some needed things, but then we still overheated on a trial run.

So I figure the only thing we haven't replaced was the circulation pump. That was today's project. I'll put in my rebuild kit parts because I bought them, but the pump rotor (as noted) was perfect.

I have NO IDEA what to do next. I've hired good mechanics, we've replaced or repaired everything. The engine runs great at dock. I can run it for an hour and I hit about 175 on the engine and 200 on the sending unit (using a IR thermometer). But when we take her out, we overheat. I've had a diver check out the intake...twice. It's fine.

Obviously I'm missing something. I'm hoping someone will read this and say "oh, I had this happen to me...do THIS..."

This is my second Volvo Penta. My first one had overheating issues too, but I sent my heat exchanger to a radiator shop for cleaning and that took care of the problem. This heat exchanger has already been to the shop during this effort.

Any thoughts would be welcome. The engine runs smooth, the raw water flow seems to be solid. My IR temps on the heat exchanger and oil cooler show that they are cool the whole time, 100°. No smoke (white or black) from the exhaust. Oil looks good, no indication of water.

[belizesailor]

On your test runs at the dock was the engine under load? What RPM were you running versus underway?

[Boracay]

Any bubbles in the fresh water coolant?

[Gator]

I can run the engine at the dock for an hour at about 2000 (quarter throttle) and the engine block is 175°. I smile and think that we've figured it out with whatever fix we just did.

Then we take it out under load. I run her around 5 knots, 2000-2500 rpm...usually less than 20 minutes she overheats. Absolutely not pushing her, again 1/4 throttle.

No bubbles that I can see. The coolant at dock is fine, but underway after 'steaming up' but before the heat alarm goes off I bring the engine down and it cools off a bit. But it does leave the basin under the engine with about four or five cups of coolant, if this is what you mean by 'bubbles up.'

[belizesailor]

The only things that seem to differ are loaded vs unloaded and moving thru the water or not.

I suggest putting her in gear at the dock and bringing the RPMs up to same level as you do when testing underway. Make sure your dock lines are well secured first of course.

[Partagas]

Old Marine Engine: Overheating on a volvo penta 2003turbo 3 cylinder diesel engine

Found a similar problem and resolution on another forum...good luck!

[Paul L]

Have you used a radiator flush to clean out the block portion of the cooling system? These passages block up with rust and junk every few years when the engines are old.

[belizesailor]

Originally Posted by Paul L

Have you used a radiator flush to clean out the block portion of the cooling system? These passages block up with rust and junk every few years when the engines are old.

Im thinking something like that too...maybe there is a hot spot or flow restriction that only comes into play when the engine is loaded and thus producing more heat...thus my suggestion to load test at the dock...this way you at least verify it is not something unique to being underway...like an intake problem which only manifests itself when the boat is moving.

Also, this is obvious but OP does not mention in his post...what about the thermostat? A bad t'stat can cause similar symptoms. You can remove and test and/or just remove and run again...if it overheats then youve found the problem.

Is the boat shaft drive or sail drive?

[Sandero]

Is the exhaust elbo blocked? How much water is coming out the exhaust?

If there is sufficient water running out the sea water system then the overheating has to be in the fresh water loop... assuming it's actually overheating. Did you measure the temp or is it the the engine gauge? Is the fresh water pump working properly?

[belizesailor]

'..if it overheats then youve found the problem."

Typo: that should have been..."if it does NOT overheat..."

[NCboatrx]

Contact Dick Vosbury at Vosbury Marine. He knows more about these old Volvos than anyone else. email Vosburym@aol.com or phone 800-427-3451

Stanley