Mercruiser Engine Misfire-Man Over Board

[Strike Force]

Sorry I had to put man over board - I had to get your attention to see if anyone could help me with this problem. I have a 2001 5.7 Ltr carborated Mercruiser with an Alpha One Drive. I recently went out on a fishing trip - went under power to the spot, shut down for some trolling and all of a sudden the motor started to run rough. Where the tach should be reading 650 it started to bounce from 2 to 3000 RPMs - pulled up gear and headed in and couldn't get it over a couple thousand RPMs and it would sputter and backfire. Changed the fuel filter - seems better, but it seemed as it would warn up it would start to miss and the tach would jump. Wondering if it could be the coil or the engine module, or the tach itself - or could a fuel problem cause the tach to jump? Not sure how fuel would make the tach jump. Thanks.

 

[Strike Force]

Re: Mercruiser Engine Misfire-Man Over Board

Posting this to get to the top.

 

[Walter]

Re: Mercruiser Engine Misfire-Man Over Board

I'm way out of my league dealing with a unit this new...but I suspect your tach is telling you something. It sounds like you've got moisture or something else causing problems in the ignition electronics. I just don't think your problem is within the fuel system...not with a tach that's making 2998 RPM swings...<br /><br />Speaking of new unit...are there any warranty considerations here? Never hurts to ask...<br /><br />Walt

 

[ed_hall1]

Re: Mercruiser Engine Misfire-Man Over Board

With a 2001 my first option would be to return under warrantee. Too soon for that kind of problem. If not an option check to see that the carburetor is bolted to the intake manifold tightly. I had a similar problem with my 21’ Stingray. Worked better with tightening, but in the end had to replace the gasket between the intake and carb. With a 2001 your gasket if not defective should still be ok. What happens is that the heating of the engine will cause the intake & carb to expand, thus allowing air to enter directly into intake. Too much air for the fuel coming into the carb. RPM’s will go all over the place. Good luck.