Need Help

[WizardsPM]

I have a 1986 Nova 42 ft, It has twin Perkins diesel 165hp, 6cly. I have one motor that the water coming out the exhaust comes out in spirts and doesn't heat up. The other the water just runs out the exhaust and does heat up. Can anyone give me any ideals on what I can check to fix this. Thanks Dave

[shakey doug]

Open engine intake filter screen, if clean turn water on with filter top off to check for unobstructed flow. If all well there, remove raw water pump face plate & check impeller for missing or split vanes also check face plate/ impeller running surface for wear exceeding 00.15.'' Another possibility is the impeller boss centre turning independent of the rubber. These are quick & easy things to do after this it starts to get a bit more involved.

[Lepke]

The engines should have an elbow at the end of the exhaust manifold where the sea water exits the exhaust manifold and is injected into the exhaust stream. It's common in older engines for rust and other debris to partially plug the elbow causing reduced flow. But several things can cause flow variances between to engines. Strainers could be plugged, heat exchanger could be plugged, bad impeller, intake valve partially closed, collapsed hose, muffler blockage and so on.
Some engines that have larger sea water pumps have a diverter that sends some water over the side w/o going thru the exhaust system. Usually controlled by a valve that is partially closed. Open - most of the water bypasses exhaust, closed - all the water goes out the exhaust.

[GordMay]

Greetings and welcome aboard the CF, Dave.