4.3 liter Mercruiser Ignition problem

[proline2550]

I have replaced both of my engines due to hydrolocking them lst season. I purchased two GM base engines from a dealer in Mass. They were manufactured in 2003 and have the late style head (8 bolt) mine were 12. I used all my old stuff on the new engines and now have a misfire coming out of both carbs at any rpm over 2000. It is non existant under and seems worst at 2300-2500 RPM and lessens slightly over 3000RPM. I have checked all the wires and caps,rotors,plugs the usual culprits. Can anyone tell me it the distibutors from the 1994 vortec (Thunderbolt IV) has any differences that would make this condition. ie the advance on the module or maybe a different distributor all together. I'm banging my head!

 

[Don S]

Re: 4.3 liter Mercruiser Ignition problem

Did you check to see if you are getting advance?<br /><br />Since you hydrolocked both engines, did you replace your risers and manifolds?<br /><br />Might try a vacuum test.

 

[proline2550]

Re: 4.3 liter Mercruiser Ignition problem

Manifolds are fresh water cooled, changed the risers last year after the first lockup. Found the cause of the hydrolocking was due to the lack of shutters coupled with the engines dieseling due to heavy carbon build up in the heads. These are long blocks, I swapped the distributors, and harmonic balancers, and carbs.

 

[proline2550]

Re: 4.3 liter Mercruiser Ignition problem

I should note as well that it is an intermittant problem. It doesn't occur the entire time the engine is at RPM. In fact they run very well aside from this misfire.