1993 MX19 Mercruiser 4.3lx
 

Hi, Everyone, im having this issue, when i hit 4500 RPM they start to surge up and down and back fires, I currently, have a 4blade 19pitch prop i hit top speed of 35-37 MPH on GPS this is at 4400RPM. any help would be appreciated, i did change a fuel line today because it was kinked going into carb but that did not solve the problem.

Re: 1993 MX19 Mercruiser 4.3lx
 

Your prop should be fine with that engine / boat and you should get into the low-mid 40's with it. The surging / backfiring is usually due to running lean but it may be time for a carb rebuild.

Re: 1993 MX19 Mercruiser 4.3lx
 

Hey, Thanks for the input, im gonna try that and ill let you know how it goes.

Re: 1993 MX19 Mercruiser 4.3lx
 

check your fuel filter also, that could be the cause of running lean if it isn't getting the gas it needs due to junk in the filter.

Re: 1993 MX19 Mercruiser 4.3lx
 

I have an 18' Diablo with the 3.0L Mercruiser and i was able to hit 4,500 RPM but now I'm lucky if it hits 4,000, full throttle is sounds like i have the anchor down, engine is struggling. Happened all of a sudden too.