Re: MERCRUISER V8 305 ONLY 3000 MAX RPM AND BACKFIRES HELP?
Sounds similar to the problem I had with my boat... anti-siphon valve at the gas tank was clogged. The difference I notice is my boat idled and shifted without stalling. Also, I could do full speed for 30 or so seconds before my carb emptied. Furthermore, my boat never backfired, it smoothly lost power. Do you stall going into forward too? If so, I would take that as you don't have a fuel restriction, because those things usually hurt your top-end, not idle. If it's just reverse, then you could still have fuel restriction, the reverse stalling could be from merc's shift assist that kills the engine for a quick sec when shifting, it may need adjusting. Does the boat act up in neutral? If it does, I would skip to the ignition system. If not, it could still be ignition or fuel related. Easiest way to eliminate fuel restriction as a culprit is to use an outboard fuel tank connected right at the fuel pump. If it fails that test, start looking at the ignition system. Start with the ignition coil and electrical. Easiest way to eliminate electrical is to attach a voltmeter to the positive ignition coil terminal, take the boat for a spin on the water and have a friend see if you are loosing volts when the issue occurs.<br /><br />The things I mentioned are probably not the fix, but these tests will help you and the forum pinpoint your problem.
