1995 454 Crusader runs hot on plane

Looking for advice on how to troubleshoot a suspected overheating problem.

I have a 1995 Mainship 31 Sedan Bridge w/twin 454s. While running on plane (3k rpm) my starboard engine is running hot, about 190-200 deg. Port engine at 160.

When idling or even at 1500 rpms, they both run at approx 150-160.

at the dock, I ran the starboard engine at 3300rpms and the temp stayed at 155 or so.

Any suggestions as to what component might cause this issue?

thanks,

Dan

Air leak before the raw water pump, bad t-stat, bad impeller, clogged heat exchanger...

Have fun!

Jeff

And add these to Jeff's list: oil cooler clogged from old zinc parts & clogged exhaust elbow(s)....

That will get you the likely suspects....best to get an IR temp gun to assist in troubleshooting.

High probability of partially clogged U Tube cooler. If you are seeing more vapor from your overheating engine exhaust - even more likely. Choices are have a radiator shop clean it out ($150) or get a new one ($400) and clean your old one for a spare. This is a common problem. The U Tube catches everything that goes past the strainer - shells, impeller vanes, weeds, etc. Good Luck.

I had the exact same problem on my '87 Tollycraft with 454 Crusaders.

After have the sea strainer cleaned, checked the through hull, replaced the impeller and thermostat, and put Rydlyme in the U-Cooler, the culprit was quickly identified as a fouled heat exchanger. Quick as in about 10 minutes. First, unscrew the zinc to drain the unit. Then remove the end cap on the heat exchanger, and pry open the end cap. Grab your smart phone and snap a couple of pictures. See the attached. Mine was partially fouled such the heat was removed at lower RPM. At cruising RPM the heat could not be removed fast enough. My fix was to have a mechanic remove the unit and have serviced and pressure tested at a local radiator shop. The repair took about 3 days. Hope this helps.