Mercruiser 5.7 overheating above 3k RPM's

[MCS59]

I have a 1996 BAyline 2250 with a 5.7 Mercruiser and a Alpha One outdrive. My problem is above 3000 RPM the gauge goes above 200 degrees. I had it to a dealer several times. They have replaced the impeller and water pump in the outdrive. They have also replaced the elbows and stated that the manifolds are clean and clear. The thermostat in the engine has been replaced also. The boat runs at 175 below 3000 rpm's. Is it possible for the water pump on the engine to be faulty. I have owned the boat for 3 years and had no problems for the first two. The dealer is stumped and so am I. any thoughts/help would be greatly appreciated.

 

[QC]

Re: Mercruiser 5.7 overheating above 3k RPM's

Have you verified the gauge with some other temp gauge/thing? IR gun? Something independent of the panel? Can you touch the manifolds? Yes, the circulating pump could be bad.

 

[MCS59]

Re: Mercruiser 5.7 overheating above 3k RPM's

I've grounded the sending unit and the gauge goes to hot. the alarm also goes off.

 

[Bondo]

Re: Mercruiser 5.7 overheating above 3k RPM's

Ayuh,... How about, Old impeller pieces in the P/S cooler,..??

 

[MCS59]

Re: Mercruiser 5.7 overheating above 3k RPM's

I dont have a shop manual yet. Can you tell me where the p/s cooler is located and how to check it? I have ordered a manual but have not received it yet.

 

[QC]

Re: Mercruiser 5.7 overheating above 3k RPM's

Take a look at the attached . . . and also take a look at The Adults Only section above.

 

[MCS59]

Re: Mercruiser 5.7 overheating above 3k RPM's

Thanks for the info. I will check the power steering cooler. I've checked just about everything and have run out of ideas other than getting rid of the boat.

 

[MCS59]

Re: Mercruiser 5.7 overheating above 3k RPM's

ok. the boat is now back in the water after I have replaced the belts and check what I could think of. I cannot find the power steering cooler. I did take the boat out for a test run. The gauge went to almost 250 degrees but but I could touch the manifolds and they were not all that hot. I figure that if this motor is indeed running that hot, I shouldnt be able to touch the manifold, elbows etc.. I am running out of ideas and patience with this boat.

 

[Don S]

Re: Mercruiser 5.7 overheating above 3k RPM's

The risers are cooled different than the engine. You can overheat the engine and have cool risers.
Did you ever get one of those IR temp guns and actually check the temp of the engine itself at the thermostat housing and the heads, and the manifolds and the risers and ...................