1994 Yamaha C115 running hot

[pepper123]

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Hey guys new to the forum,have a issue if anybody can help with?
Just got a older CC with 94 Yamaha C115 on it and its running hot and shutting down,I did check thermostats,and sensors checked fine. I did redo the WHOLE water pump/impeller assembly ( had a stronger tell tale flow).

After starting takes about 10-15 min. to get hot (going by gauge) also I did replace the poppet valve with the newer mushroom style. Removed the TS covers and after a min. or so water does flow from the holes. Also the weird thing is the alarm doesn't go off but it does work as I have checked that as well,and if I remove the temp sensors from the head while running the gauge still reads hot (doesn't move) and the alarm doesn't go off?? Iam no marine mech but Iam stumped,any ideas?? thanks

 

[robert graham]

When you did the water pump did you inspect/replace that plastic water pump body?....

 

[tommarvin]

First, a CC with a Yamaha my dream,I'm jealous, overheat is three things, water pump/rubber impeller, thermostat, put in a pan of cold water heat slowly what temp does it open, and a overheat sensor or gauge that's bad, test with an IR thermometer point it at t-stat housing after start up.

You said your running hot, how do you know your running hot? and does the motor shut down completely and stop running?,

Waiting a min or so for water to flow from the holes seems to long, we see water in 5-10 seconds, how did you test the alarm if I may ask?

The gauge is broken, it doesn't move?, the alarm doesn't go off because the motor isn't hot? aim IR thermometer at t-stat housing it should never get to 180F or higher. Our force 125 overheat buzzer goes off at 180F. Please tell us what you find out so I can learn something,Is it a 19ft CC?

 

[Melbournite]

Any chance the coil could be breaking down once it gets hot. You could test the spark plug leads & coil resistance and voltage with a multi meter also you could get a spark tester to test the spark. Only a suggestion as I'm no expert but have had similar issue and still working on it but have found a break in the spark plug leads