I put a small hand transfer pump on the fitting and used it to drain the tank. It took very little effort. So the valve could work as designed and fail to work at times? Next time it happens I will park the boat for an hour and if it then works it is probably the check valve? Correct? Then...
I have a 2015 175 Bayliner with Mercruiser 3.0. It will run just As it should, but an hour in it will lose power at high speed. Runs well at idle and low speed. Replaced the fuel pump, drained the Tank through the supply line to engine. This convinced me that the tank had no water, the check...