Re: 90 HP MERC TROUBLES
Don't know if you have a thermostat. That sounds like a "stuck closed" stat with no bypass valve working in conjunction with it.....which Merc's have nowadays.<br /><br />I had an OMC 70 hp once that the stat was going out. It would stick more and more each time I used it. Same type problem. The pistons/rings would get hot and swell up in the cylinder and the moving friction slowed the engine down.<br /><br />Finally this baffling performance came to an abrupt end. I was running at WOT one day, right out of the ramp (no wake zone) and it siezed up tight. Boat came to a complete stop real fast.<br /><br />Upon teardown at home later, I had galled aluminum all over everything in the cylinders. I didn't even know it had a stat.<br /><br />Once you determine if you do, and if you do, take it out and test it in a pan of slowly heating water. 120 degrees to start opening is a popular number for outboards.<br /><br />Next, pull your plugs, all of them, and inspect the cylinder walls of all the cylinders (thru the sparkplug hole) and look for galling. With just 40 hrs on the engine, the crosshatch honing pattern should be nice and even and clearly visable. Possible that the walls may have started to shine up.<br /><br />HTH,<br /><br />Mark
