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Mercruiser 5.0 MPI Half Power

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jed992

New member
Picked up 2010 Crownline 210LS w Mercruiser 5.0 MPI SN 1A611023 a week ago. Started fine, but seemed a little rough. Initially, could not plane and get revs above 2000rpm. Seemed to clear itself out and ran fine after 15 mins. Wrote it off to old bad gas, even though I had added 1/2 tank of fresh. Tried both batteries which seem fine at 14V running. Same issue 2nd time out, so still suspecting bad gas. Burned 3/4 of the tank and filled it up with premium. Now problem seems to have gotten worse with rough start and not clearing after 20 mins. At WOT, it seems like something is cutting in/out, as it sounds like it wants to go. Seems to be running on half power. Tried pulling injector #2 plug while idling at dock and no noticeable difference in sound/revs. Same with #4 injector. Pulling #6 injector does cause it to stumble, but not stall. Seems like # 2 & 4 are not firing. Will test others tomorrow. Tried reseating the 10-pin and any other connectors easily accessible. When idling pushed down on interrupt switch and it stalled. I can see the neutral safety switch, but not sure how to test it. Haven't check distributor, rotor and plugs yet?
Any ideas appreciated.
Thanks,
Jed992
 
Ayuh,...... Pull the fuel filter, 'n examine it's contents for anything but clean fresh gasoline,......
Adding fresh gas to bad gas, makes more bad gas,.....
 
Thanks. Assume I can just disconnect power from fuel pump and then remove fuel filter slowly with rag to catch any pressure spray?
 
The cap and rotor on these are known problem areas, at least in humid moist environments. I buy the NAPA Echlin equivalents. Many threads out there on this issue.
 
jed992 said:
Thanks. Assume I can just disconnect power from fuel pump and then remove fuel filter slowly with rag to catch any pressure spray?
Click to expand...
Ayuh,..... The fuel filter should be on the vacuum side of the fuel pump,... so no pressure, just gravity,....
I prefer to use a catch-can, 'n a rag,.....
'n there's no reason for the key to be "on" when changing the fuel filter, so no reason to unplug it,....
 
Update. Changed Fuel Filter - fuel looked fine. No improvement. Changed distributor cap and rotor. Cap contacts looked corroded, but still no improvement. Finally changed plugs and that did it. Full power and running great. Thanks for the tips.
 
jed992 said:
Update. Changed Fuel Filter - fuel looked fine. No improvement. Changed distributor cap and rotor. Cap contacts looked corroded, but still no improvement. Finally changed plugs and that did it. Full power and running great. Thanks for the tips.
Click to expand...
Thanks for posting the fix. Can you provide a bit more detail? Were the plugs the wrong ones? Were they just too old and worn?
 
This is a teaching moment for you. Any time you get hold of a new-to-you boat, unless the PO hands you the log books that show the full service history, you must assume it will need everything. That means a complete tune up with plugs wires cap rotor (points condenser), all new belts and hoses, hose clamps, water pump impeller, circulating pump, manifold gaskets, fuel system plumbing, and a full inspection of the drive and engine mounts. I know this sounds like a lot and it can cost several hundreds of bucks. But boy oh boy one stranding with the SO on board and that'll seem like peanuts. Yes, cry whilst you turn the wrenches, but it'll save you in the long run.
Document these actions even if it's just jotted down on a post-it somewhere. Keep good records.
 
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