6.2 running hot above 1500 rpm.

[39rolls]

I am having trouble with a 2008 6.2 merc. with 88 hrs running hot above 1500 RPM. What I have done so far: replaced sea water pump, Therm. rep., bravo 3 outdrive pulled and checked for kinked or bad hoses. Tried backflushing engine after out drive pulled and does seem to have some back pressure. Any ideas please.

 

[achris]

Re: 6.2 running hot above 1500 rpm.

Check the hull to ensure you have a smooth and uninterrupted water flow to the pickup. If the pickup is through-hull, make sure also that it is facing the right way and not 'spun' in the hull...

 

[Prophammer]

Re: 6.2 running hot above 1500 rpm.

Did you verify engine temperature somehow? like with an infared heat gun, aiming at top of engine, risers, water neck, etc? I don't think it should read above 140 at any of those locations.

 

[tazrig]

Re: 6.2 running hot above 1500 rpm.

Are the exhaust elbows cool to the touch? Is your engine raw water cooled or fresh water cooled? When you replaced the water pump Impeller were all the splines still on it? If not pull off the t-stat housing and start looking for the missing piece or pieces. Feel in all the openings of the t-stat housing with you finger sometimes they like to hide (get stuck) in there and block water from getting through. Also if your engine is fresh water cooled try pulling off the ends of the heat exchanger and seeing if maybe you didn't just pick up some sand in the raw water tubes. Let it flush out if you did.

 

[Don S]

Re: 6.2 running hot above 1500 rpm.

What are you calling hot? 170? would be normal for a raw water cooled engine, and 180? for a Close cooled engine. As mentioned, verify the temp with an IR temp gun, then you know it's not just the gauge, sender, or wiring problem.
What's your WOT rpm?

 

[39rolls]

Re: 6.2 running hot above 1500 rpm.

Above 2oo and climbing over 1500 rpm have verified with a infared gun. Thanks

 

[39rolls]

Re: 6.2 running hot above 1500 rpm.

water is pulled up through the foot see no problems in that area. Thanks

 

[tpenfield]

Re: 6.2 running hot above 1500 rpm.

Intake obstruction in outdrive or transfer tube within transom assembly. Been there, done that. . .

 

[39rolls]

Re: 6.2 running hot above 1500 rpm.

Elbows not cool to the touch raw water cooled, replaced impellar first no splines missing then replaced complete pump, cleaned sand filter have not tried to feel in the t-stat openings but will. Thanks

 

[Don S]

Re: 6.2 running hot above 1500 rpm.

water is pulled up through the foot see no problems in that area. Thanks

You won't see a problem, but that doesn't mean there isn't one. Plumb in a piece of clear hose on the raw water pumps inlet fitting and go for a run and see if you see air bubbles in the inlet stream, if you do, you have a leak that is allowing air into the system.

Here is a Volvo document that explains how to test systems with engine mounted raw water pumps.
Might just help you find your problem.

View attachment VP Overheat Diagnosis.pdf

 

[tpenfield]

Re: 6.2 running hot above 1500 rpm.

You mentioned backflushing engine . . . did you backflush the oil cooler? that is usually in between the sea water pump and the thermostat housing. Been there, done that too :facepalm:

 

[Prophammer]

Re: 6.2 running hot above 1500 rpm.

You mentioned backflushing engine . . . did you backflush the oil cooler? that is usually in between the sea water pump and the thermostat housing. Been there, done that too :facepalm:

I aggree, I ran into a VP last year that cooler was stopped up with impeller rubber from ....... not the last impeller.......but the impeller before that! The mechanic that did the impeller before the last impeller, didn't mention to anyone that some of the vanes were chewed off.......