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I’ve got a 2006 5.0 mpi with 500 hrs on it. It had new

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I’ve got a 2006...

I’ve got a 2006 5.0 mpi with 500 hrs on it. It had new manifolds and risers 12 months ago, 40 hours use since. Have noticed rough idle and needs a bit of throttle to start, then low power on take off and then comes on to all 8at about 2500 rpm. ( starts and idles on 7). Pulled plugs, all good except #1 cylinder, which was wet /showed water on plug. Como tested this cylinder and read 200 psi. Suspect manifold gasket?if plug or ignition problem only, can cylinder draw in water when not firing?

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That’s all the info so far

Submitted: 7 months ago.Category: Boat
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Answered in 14 hours by:
1/13/2018
Marine Mechanic: Boat Doc, Boat Enthusiast replied 7 months ago
Boat Doc
Boat Doc, Boat Enthusiast
Category: Boat
Satisfied Customers: 242
Experience: Expert at Just Answer
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Hi, sorry for the delay. It will not draw water in if it doesn't fire, unless there is also a compression issue like a leaking valve. But since your compression is good, we have to suspect water entering from either the riser gasket, intake gasket, or head gasket. So the first step is to pull the riser on that side and see if there is water trace. If it shows no sign then you will probably have to pull the intake to inspect that. If no sign of leakage across the intake, then you have to pull the head, but you are about 2/3 way there with the intake off. I really don't think it's a head gasket though since you have such good compression. (Although it could be the head itself.)

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