Yamaha 90ETG 1988 Forum

Today I took my boat out for the first time this season (after being stored all winter). My 1988 90ETG Started with no problems, however as I started to idle away from the dock I heard the engine warning alarm (for the first time ever !). I turned around and idled back to the dock to check it out. I assume this warning indicates an overheating problem (although I could not confirm this by referring to my Yamaha 70G/90G Service Manual - could not find any reference to warning alarm in it). I Noticed the engine did not seem to be pumping any water at idle. When I raised the lower unit out of the water and inspected it, I discovered that the Trim Tab was missing. This is an obvious problem that I need to fix, however a missing trim tab does not immediately scream "engine overheat problem", but what are the odds of 2 unrelated problems occurring simultaneously ? Also the proximity of the trim tab to the water intakes on the lower unit, and the gaping hole left by the missing trim tab suggests that the problems could be related. Perhaps the trim tab opening makes it impossible for the water pump to extract the required cooling fluid from the lake. My question is, should I replace the trim tab and expect that alone to solve my overheat warning alarm problem, or should I be looking for a deeper problem ? If so what ?