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Engine does not run right above 3300RPM after warm

D

dmmmm

New member
"I have an '84 mercuiser I

"I have an '84 mercuiser I/O that runs great until it warms up. After it warms up it will not run right at speeds above 3300RPM. It surges as if there isn't enough fuel in the bowl. The motor is a 152 cubic inch GM motor. I have replaced the rotor, points and condenser, dist cap, wires, plugs, fuel pump, fuel line, fuel filter, cleaned the fuel tank, cleaned the carb and replaced the seals and check ball and adjusted the float. I'm out of things to replace - any ideas."
 
Perhaps the engine is having a

Perhaps the engine is having a vapor lock???? Does it do this if you run the boat without the cover on the engine where it can get plenty of air intake?? Air filter clean and clear?
 
"Yeah, that is a classic coil

"Yeah, that is a classic coil symtom. Coils are rarely a problem but when they do go out, missfire at high RPMs, especially with heat, is a very possible sign of a weak coil. Be sure to get the correct replacement. Some coils require external ballast resistance and some do not."
 
"Just another thought, if it&#

"Just another thought, if it's not the coil...
Is the choke opening all the way? It would spew dark brown smoke along with running like crap."
 
Are there restrictive fuel FIL

Are there restrictive fuel FILTERs (not strainers/ water separators) before the fuel pump?

Jeff
 
"There are no restrictive fuel

"There are no restrictive fuel filters. The cover is a long way from sealed, so I really doubt that is the problem and the flame arrester is clean. I will try the coil though; thanks for the suggestions."
 
I had a similar problem on a S

I had a similar problem on a Sea Ray I used to own. It happened twice. Once it turned out to be the little inline fuel filter in the carb right at the fuel inlet. The other time it was the breather vent on the fuel tank. The sceen had gotten clogged. An old toothbrush and some solvent was all it needed. It's nice when you don't have to spend money!
 
I encountered a Very }similar

I encountered a Very }similar problem with a 2003 496MAG last fall. This turned out to be a worn raw water impeller. Once the raw water pump (complete) was installed the problem went away.
 
"try pressure testing the mani

"try pressure testing the manifold water does not burn very well ,crakes open up when manifold gets warmer wont see water in oil either"
 
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