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4.3 Mercruiser losing power under load

T

The Lazy G

New member
Had a cracked block and replaced the engine with a new remanufactured unit. As everything was functioning properly my mechanic put everything from other engine on new block. Break in seemed to go well but as i wrapped it up and began normal use the issue began. Starts, idles and runs fine till about 3,000rpm then cuts out and starts to balk. Replaced fuel pump, lines and filter. Cleaned carb, plugs and wires are good. Could the Endlebock Carb be worn out? Or could this be some kind of electrical problem. Original engine was a 1988 so other parts could be original. Guess lesson to be learned: spend the money and replace it all. Any thoughts would be appreciated.
Thank You
 
Have you started running any tests or diagnostics? You say plugs and wires are good. Did you test to make sure you are getting good spark? Have you checked cylinder compression? Have you checked timing?

I am currently running the same 4.3 GM 6 cylinder on my boat, but with the OMC outdrive. Good luck!
 
What ignition system? If it’s an original OMC Cobra 4.3 of that year it will have points ignition which requires maintenance.
Other possible causes:
Debris/water in fuel
Stuck/corroded anti siphon valve on the gas tank
If this is a pre Vortec 4.3 the hydraulic lifter preload should be set when setting up the reman engine….was this done?
 
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