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1978 25hp rpm issue

Kilibob

New member
Hello,
My outboard starts fine but while initially running the motor at lower rpm's, say for half an hour, the thrust noticeably increases without changing the throttle position. It's as though one of the two cylinders finally engages and contributes power to the load. I thought that maybe the problem was a reed valve malfunction. But they both look fine. The carburetor has been rebuilt and the motor runs fine at WOT. Any suggestions are much appreciated.
Thank you
 
Start the engine and monitor the head temp it should get hot to the touch in a few minutes. If it stays cool replace the thermostat and flush it out with saltaway in a barrel for about 15 minutes. It should get hot enough you want to pull your hand away but dont have to for a slow count to six. It sounds like your thermostat is stuck open? Also do a cylinder drop test on a cold start. Pull a plug wire and quickly put it back on. It should stay running on either cylinder. If it stalls the one you pulled is the one thats working.
 
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