'78 cd27 ysb8 cooling system

[aigen]

Hello,
I'd appreciate any help out there. I'm wondering if my water pump is shot. The impeller doesn't appear damaged, but no water shoots out the exhaust, so how to check what needs replacing? Thank you.

[okawbow]

First thing....be sure you have your inlet water valve turned on. Check the hose, strainer, pump inlet, etc. for blockage. Try pumping from a bucket of water. Maybe your hull fitting is blocked by weeds? Be sure the pulley isn't spinning on the water pump shaft. Install a new impeller. The old one may be spinning on the metal hub. Check for blockage on the out-lines of the pump. Inspect the cover plate and inner surface of the pump for wear lines. If deep grooves are present, order a new pump.

[mgphl52]

Don't forget to check for a scale build up in the exhaust elbow. I've had this happen before.

[fsuhre]

Had a similar problem with the YSM8 in my CD27(1978 #101). Two years of intermittent overheating. Overheating almost always occurred after restarting the engine after it had been used 30 minutes to an hour then off for a few hours. As a result I became proficient at removing the water pump and checking the impeller, checking for potential blockage, flusing the system, and replacing the thermostat. Since none of these actions seem to make a difference, I finally replaced the water pump. Overheating alarm has not sounded in 18 months. Still don't know what was causing the olds pump to malfunction. Good luck in solving your problem.
Bart

[bobc]

I had this problem happen when a hose kinked. I had replaced the raw water strainer, so the problem was somewhat self-inflicted. The odd thing was it didn't happen right away.

[Bob Owens]

Bart,
What you describe is almost exactly what I am having--described below under the post about suspected bad temperature send unit. Maybe my send unit is not bad and I really am overheating. Did you ever figure exactly what was wrong with your raw water pump? Thanks.
Bob

[fsuhre]

Bob,
I never did figure out what caused my old water pump to malfunction. From my limited knowledge it appears the water pump is simply an impeller driven by a pully attached to a shaft. If the pully is working, the impeller is in good shape, the thermostat is working, and there is no blockage then why was I having intermittent overheating after restarting the engine? I surmised that an internal component of the pump's drive mechanism was failing. Maybe a seal or a bearing ??? Anyway the good news is that a new water pump eliminated my overheating problem.
Bart

[Carter Brey]

Check also for air leaks in the upstream part of the circuit. I had bad cork seals on my raw water strainer; the vacuum was compromised and little water was getting in as a result. The symptom there was steam and reduced output at the exhaust. As long as I ran the motor above 2000 rpm it managed to pump enough water to itself, but below that it overheated.

Carter