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Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 10903
Experience:  40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
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I have a 2002 5.0 mercruser with TBI having some issues. the

Customer Question

Hello, I have a 2002 5.0 mercruser with TBI having some issues. the boat starts and idles fine, however when opening up to full throttle from a dead start the motor has some hesitation, it will bog slightly and not go past 3000 rpm, as the boat starts to plane off and it is trimed the motor will go to 4000 rpm, but I have to play with the throttle position, backing off then pushing it down to full open position. the motor will not go past 4000 rpm. when the plugs were pulled they were on the wet side, there was no one plug worse than the rest. the cap and wires were checked, upon pulling the coil wire I noticed lots of oil on the wire and down in the coil, I changed the coil, plugs, fuel filter, cleaned the cap with some fine sand paper, I took it back to the lake, still the same problem.. the is a lot of what looks to be unburned fuel (black soot) under the swim platform.
can this be a timing problem.
Submitted: 1 year ago.
Category: Boat
Expert:  Tan replied 1 year ago.

Hello. My name is Tan.

Timing won't cause a soot issue. The engine starts and idles fine.

I would start with checking fuel pressure(spec. 30 psi) at the throttle body. Rich running condition is either the fuel pressure regulator or the ECT (engine control temperature) sensor.

The other possible issue is fuel starvation. This would cause the lack of rpms and the stumbling. I think you have 2 issues here. Run the engine on a different fuel source to eliminate the fuel starvation possibility.

Can you do these checks?

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