Even a good guess might help

"I posted this earlier and did

"I posted this earlier and didn't get much response. 1998 carb merc 150 offshore that had possible stator problems. after running thirty minutes or so and then idling for five minutes the boat would not plane out again until cool. Turns out all ignition and timing issues are fine. Fuel and filters are fine. mechanic has cleaned carbs and replaced needles and seats and adjusted floats and now boat won't plane even the first time. He says he thinks it may be excess pressure delivered by the fuel pump because of a broken sealing ring in the crankcase allowing crankcase pressure to be erratic. he says on this motor it is like each cylinder has it's own crankcase. This motor has under 75 hours on it. Does any of this sound possible? Any ideas on what else could be the issue? HHHEEELLLPPP!!!
Compression is fine on all cylinders and oil injection is working correctly, ignition systems testing during failure and they all work correctly. Someone on another board suggested an exhaust problem?? Not sure about that one or where to start.. Plenty of fuel is being delivered to the cylinders but apparently too much."

"Additional questions I asked

"Additional questions I asked the tech..this may help
I spoke with the tech and these were his answers (btw he is happy for the help and will be checking the board later)

Is the tech using a DVA meter when determining if the ignition system is working? Yes, mercurys brand converter

Is he able to measure the peak voltage at the plug...to see if a cyl or two is cutting out? No, voltage is too high for him to measure

Has the engine been ran on a dyno? No, there are no dyno available here except at the college

Is there fuel going into all the throats when off idle? Yes, there is usually a fine mist from the emulsion tube when accelerating on most models but this one looks more like a dirty fuel injector..not quite a stream but more than a mist and not continuous and it is the same on all six throats. I asked him about his fuel pump pressure readings and he said "fuel pressure measured on the outlet side bounces quickly back and forth from zero to pegged (10 psi max reading) normal operating range for this motor is 2 psi at idle to 8 psi at WOT. He said the readings were the same when checked at idle thru 2500 rpms.

Is there black inside the prop...or on the back of the boat? No more than would be normal, he estimates motor has less than 100 hours total."

as long as thee is pressure yo

as long as thee is pressure your fine
how is the vent lines and how are the fuel lines
if you do not use the boat much the rubber on any fuel lines can get really hard

so he has check cdi inputs and out puts

i believe that motor has high and low stators

the guy to ask is bandit on here he is a master merc tech

"Yeah, I have been following t

"Yeah, I have been following this. If the ign. takes 30 min to crap out, it going to be a S.O.B. to find. 0 to pegged might mean the fuel pump check valve (out) is bad. Fuel pressure should be stable. Worth a closer look I think."

fuel pump was rebuilt and chec

fuel pump was rebuilt and check valves replaced 9/15/07. it craps out immediately now. ignition is fine even in failure.