Same story, same problem for 3 years. My 3.0 merc. runs like a new engine for 15 to 30 minutes. Never misses a lick. It slowly starts to sputter and I back off the throttle and it runs ok for a few minutes and then continues to sputter until it quits. After An hour or so it will restart and run ok for maybe 3-5 minutes and stutters again. It will hardly run by now. It does have fuel and spark at this point. Also, if I hit the trim before I start having the stuttering problem, all is well. If I try to trim it after it starts acting up ,it nearly kills the engine. Hmm !
Have replaced dist. with a rebuilt one, points, condenser, cap, rotor,plugs, wires and coil. New battery and rebuilt alternator. New fuel filter in the pump and carb. Carb. has never been rebuilt, but my way of thinking is, the carb. is ok if it runs so well for the first half hr. or so. Accelerator pump squirts a strong stream after it has quit. Am I wrong ? It also has the original fuel pump. The boat is a 91 Sea Ray 170 that I purchased new. I know there is a guru here with an answer. I hope! I'm stumped and sick of this thing.
Have replaced dist. with a rebuilt one, points, condenser, cap, rotor,plugs, wires and coil. New battery and rebuilt alternator. New fuel filter in the pump and carb. Carb. has never been rebuilt, but my way of thinking is, the carb. is ok if it runs so well for the first half hr. or so. Accelerator pump squirts a strong stream after it has quit. Am I wrong ? It also has the original fuel pump. The boat is a 91 Sea Ray 170 that I purchased new. I know there is a guru here with an answer. I hope! I'm stumped and sick of this thing.