I thought this May help some people , I recently was working on a 1994 Mercruiser 4.3 thunderbolt IV motor , first time in water the motor would bogg it you tried to give it full throttle it would only do 35 top speed seem if it was staving for fuel. So I pulled the 4 bbl carb and cleaned and rebuilt it took out to water again same problems and then was popping thru intake so I said had to be a coil , so I had an extra coil I thru on it and put new plugs and wires in it and it seemed worst , so I replaced the rubber feul line and the check valve in the tank , and it was worst the next time out so I lifted the motor cover and watched everything and caught the coil arcing out the side , so I put another this time brand new out the box coil I go back to lake and water was really rough and it was still bogging and then motor shut down wouldn't start back up and I knew had to be dam exhaust flappers and I was right they had fell apart so new flappers and I starting checking all my connections I took off all grounds and I put a heavy gauge ground wire and cleaned the studs on motor , then couldn't get to start the starter bendix wouldn't kick out fully would just spin real fast so back to checking all wiring again to starter and alternator and in harness . Then I went to front of boat to ignition and looked under dash and noticed someone had unplugged the buzzer under dash from ignition and I seen the ignition I guess they didn't tighten the wires back down and the screws holding them tight were about to fall off so every time I would go out I was losing connection at the ignition switch and it just got worst and worst I tighten the ignition wires and everything was fixed no moroe bogging boat will do 55mph on water now and starts right up ! Thought this may help someone hopefully because I went crazy chasing the problem down !
