Run of bad luck...

[nola 521dvx]

04 225 HO DI motor, rebuilt 30 hrs ago, has been running great until past week. Has what appears to be a slight base gasket leak (oil on midesction after storing) which I was getting ready to fix - then it developed a miss last weekend, worse today. Happens only after motor has run perfectly normal at speed for 5-10 mins then gets progressively worse, to where it misses/bogs even at 1000 rpm, but generally idles fine. Hooked up software and 12/40V outputs are fine, CPS checks out, exhaust pressure varies with throttle as problem occurs. Circ pump (priming) and lift pump pressures (at idle) check out fine, as does lift pump vacuum, no water in filter. The apparent temp dependence has me thinking coil or coils - what do y'all think? Need to check coil and circuit resistance and primary voltage but couldn't these be normal unless measured when the problem is happening? Hard to do. Appreciate expert insight into this problem.

Just to make things even more "interesting" I found the head of an upper crankhead bolt in the belly pan - definitely not overtorqued during rebuild, what in the world could cause this? There is zero wobble at the flywheel.

Computer was repaired 5 hrs after rebuild by DFI - oil injector circuit short.

Looking forward to getting these issues behind me!

[SEAHORSE]

Did you do these checks while the motor was on the water acting up, or just at the dock?

[nola 521dvx]

All except the fuel pressure checks were on the water with the motor acting up. I don't have the circ pump pressure adapter so measured priming pressure by rigging a gauge between the pump output and return manifold barbs on the pump assembly, 30 psi priming, 18 or so steady when pump stops. Lift pump vacuum (basically zero) and lift pump pressure (6 psi stable) both measured at idle on the hose pipe.

The good when cold bad when hot behavior has me thinking coil but I rigged up a timing light and ran the boat on the water and honestly couldn't see a difference in rate of flashing on any plug wire even while the motor was falling on its face. I probably need to run the fuel pressure tests on the water with the motor acting up, if I can fashion an adapter for my gauge (the BRP tool is $$$$).

Forgot to mention also compression on the cold engine was 130 all around.

Appreciate your thoughts on this and the broken bolt, want to get back fishing.

Update - measured coil primary and secondary resistance and circuit resistance from J2 plug to ground - all within specs, coils and grounds look fine from what I can see. I'm back to thinking fuel, need to run the tests on the water.


Modified by nola 521dvx at 12:45 PM 11/28/2010

[nola 521dvx]

Update. The great folks at Magnum Outboard lent me their adapter so I could meaure fuel pressure on the water. Ran for a couple mins at 40 psi (a tad high?) with no issues, then fuel pressure dropped to 5 psi, engine bogs down, pump not running. Turns out fuel pressure relay is intermittently switching off - switched it with the trim down relay, boat runs great but trim starts acting up intermittently! Gotta love a $25 fix.

Service manual says pressure should be 20-30 psi - is 40 psi something that warrants pump replacement (assuming no restriction in return manifold)?

[SEAHORSE]

For excessive fuel pressure, remove and clean out the filter inside the vapor tank connection where the return line connects. Use a needle nose pliers to remove the conical filter. It is replaceable if it cannot be cleaned.

[nola 521dvx]

Thanks Seahorse - I didn't even know there was a filter there.