Yamaha 1998 250HP OX66 sneezing, cylinder cutting out, etc...

[CarlS717]

I'm at wits end. I've had at least two Yamaha certified guys work on this engine (Model S250TXRW) and we've replaced darned near everything in it, yet it continues to sneeze at low RPM, at around 1600 RPM a third cylinder cuts in and out (I think it's the top right one, but not sure), and when it's really feeling like ticking me off it MAY get to 4200 RPM at WOT. When it's not it gets to about 5100 but takes its sweet time getting there. Right now it's dripping oil all over the motor well (tilted up, which I'm told isn't unusual) and since the tilt motor just died there it shall stay until I decide this thing is worth more aggravation (or money).

She has new lp pumps, VST pump, gets 35 lbs at the rail, and we've soaked the injectors for a couple of weeks. Compression is 110 +- 5lbs all around. We've replaced lots of electronics. We've adjusted the TPS like crazy. Plugs look kinda odd, a touch of water on two of them, carbon on a third. Thank goodness my guys like valium, but we're all throwing up our hands. Rodbolt17, HELP!!!!

Thanks.

[rodbolt17]

first thing I would do?
put the wrenches down, back away slowly.
then I would look at how the system is designed.
from idle to 850 RPM cyl 5 is shut down,from 850 to 2000 RPM cylinders 5 AND 2 are shutdown.
then I would use my diagnostic test lamp and see if code 1 appears.
if it does then continue.
the lamp will only flash a code if the code is currently active thats why you have to leave it hooked up when testing.

with the diagnostic lamp installed automatic transfer is inhibited but manual and all alarms still function.

water in the cylinder is what I would look very hard at,most likly would remove the heads for a visual and to test the surface flatness of the head.

this system isnt hard but you must know what it does,when and why or it can zap ya.

[CarlS717]

Thanks! Should I do the head before I mess with the tilt motor?