Please help, going broke on trying to find fix.

[GreatLakesPirate]

5.7 mercruiser stumble backire

1993 5.7 mercruiser. Engine runs fine but stutters and backfires around 2500 rpms and up. Could a faulty alternator creat the problem by insufficient voltage to coil/ignition system. I believe its a delco ignition system. Try to post sound video of issue.

 

[GreatLakesPirate]

Post #1,
My 1993 5.7 mercruiser. Engine runs fine but stutters and backfires around 2500 rpms and up. Could a faulty alternator create the problem by insufficient voltage to coil/ignition system. I believe its a delco ignition system. Try to post sound video of issue.

Post # 2,
My mercruiser 5.7 runs fine till about 2500rpm then starts to engine miss and backfire. My mechanic is breaking the bank on me, could a faulty alternator cause the coil to create this issue. Carb rebuilt, fuel system pressure tested, new plugs, distributor and wires. Same running issue no matter what hes done so far. I had the alternator tested and it was fried, could that cause the misses and backfires?

 

[Scott Danforth]

first, welcome aboard

second, since the 5.7 (350 cubic inch GM motor) has been in boats with 8 different fuel systems, 4 different block families and 6 different ignition systems over the past 60 years. please help us help you by dialing it in a bit. like year, serial number, fuel system, etc.

what causes missing and backfiring is running lean and improper timing.

we cant help you unless you tell us what you have.

 

[tpenfield]

:welcome: to iBoats . . .

Sounds like your mechanic is paid to replace parts rather than solve problems. As Scott mentioned, we will need to know the specifics of the engine (Serial #). Often posting a video of the engine in action (or acting up I should say) can be helpful as well.

 

[gm280]

Does the problem clear up pass that 2500 RPM range, or is that as far as you can get it to run?

 

[Scott Danforth]

being a carb and popping and sputtering, would focus on fuel quality (pour the contents of the fuel filter into a clear container and look for contaminates)

would also go back to the carb and verify that each and every passage is open. usually requires running a fine wire of fishing line thru every drilled passage.