I has a similar experience a couple of months ago. My Universal M35B was out of the boat for replacement of a broken motor mount. When the engine was started at launch, no water came out of the exhaust.
We started checking the usual suspects to diagnose the problem and finally determined there was no water output from the raw water pump. The impeller looked great - only 108 hours on the engine after all - so we were going to put it back in the pump. In the process of turning it into the cavity in the pump, we noticed that the hub turned but the vanes did not. On closer inspection the hub had lost its bond with the rubber part of the impeller. Our guess is that the vanes had excessive friction against the cavity of the pump while still dry , and the torque at startup broke the bond. So we installed the new impeller with LOTS of grease in the cavity. And I will remember the incident when I replace the impeller in a year or two. Rick Brass Washington, NC : CnC-List [mailto:[email protected]] On Behalf Of Steve Thomas Sent: Friday, October 19, 2012 11:14 AM To: [email protected] Subject: Re: Stus-List Miscellaneous -impeller I helped a friend of mine bring a new to him Cal 25 from Munro Michigan to Port Stanley last year. He had a borrowed Mercury outboard which he freshened up with spark plugs, raw water impeller, and I don't remember what else. He also tested it out both in a barrel and on the boat when we got over to Michigan. We left Munro, no wind, and about an hour out into the channel the motor started to falter and after a few starts and stops we hauled it aboard and disassembled it in the cockpit. Since the exhaust exited underwater, it was not immediately apparent to us that the problem was the cooling system. To make a long story shorter, the new impeller had failed by the rubber coming unstuck from the brass centre. It was a brand name part, and not a knock off. Never expected that sort of failure, and I don't know how you could protect against it except by keeping a spare on board, perhaps of a different manufacture date. Steve Thomas C&C27 MKIII Port Stanley, ON
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