Overheating problem

[Legacy]

Hi all. My starboard engine temp gauge spikes once I go over 1900 rpms. (Cummins 370) Under 1900, it's rock steady but about 5 degrees warmer than the port engine. Here's what I've done so far to no avail.
Checked coolant (fine and less than a year old)
Changed oil and filters, all fine
Checked all fittings, hoses,etc. (all fine)
Cleaned out sea strainers and thru hulls (all fine)
Replaced impeller (it was fine and intact)
Replaced thermostat
Checked water flow (strong) and inflow and outflow temps, all fine

Next steps. Replace the water pump as it seems to have a very minor leak but may increase under load.

Then what? Heat exchangers? Aftercooler? Bring mechanic on ride to trouble shoot?

Ideas welcome.

Rick

[jleonard]

You forgot the most important of all trouble shooting steps, or you forgot to mention it.
This should always be number one.
Did you verify that your temp gage is accurate by using a heat gun?
Here's one that got a friend of mine with a Cummins....his sea strainer cap was not 100% sealed. Although it didn't leak, he sealed it on my recommendation using grease on the threads. Instant 10 degree temperature drop. He was sucking just enough air to reduce the flow at higher rpm.
Another friend saw a 10 degree drop when he installed a new raw water pump. His impeller was good, but the housing and nore importantly the cam was badly worn.
When was the last time you cleaned out the heat exchanger? I do mine every 2 years regardless of hours.
Also make sure your intake water hose is not delaminated and collapsing and restricting flow. Yes I know you said flow was fine but I assume you mean "visually" fine. You could be 3/4 flow and not realize it?
Just a few quick thoughts based on what I have seen many times.
Hope it helps or triggers some ideas.
Good luck.

[RobS]

Rick,
Since Legacy is a twin screw swap the wire connections btwn to the temp gauges to eliminate a possible bad gauge. You can do the same with the senders too.

[Legacy]

Thanks gents. All good ideas. Hopefully the answer is out there! Despite what my cold-adverse wife says, November still allows for some good tuna fishing!

Rick

[TD]

Here is what I found to be my slightly higher temperature problem.

Aftercooler Port2 9 09.JPG

It looked like this after I cleaned it. Also found a slight leak in the aftercooler and had it resoldered.

DSCN1599.JPG

[RobS]

Can't hurt to try this:

viewtopic.php?f=7&t=2054&hilit=rydlyme

[TD]

The air side of the aftercooler can also be the problem--they get pretty sludged up if you haven't cleaned in over 3 years.