1990 150 ProV Strange Issue

[mitch00]

Heres how the problem started. The motor was running great. 5300 RPM's @ WOT. Then after a trip I filled the tank on the way home and took it out the next weekend. The motor idled rough as soon as I started it. Mid-range it ran fine but at WOT it would run for about 10-15 seconds then bog down until I pulled the throtle back for about 10- 30 seconds then it would do the same routine. This is what I have done so far. Compression check, all cylinders range from 105 to 110. I rebuilt the carbs...installed a water/fuel seperating filter...replaced the fuel lines and primer bulb...tested the fuel pumps. Still with the problem. Tonight I started the motor in the dark to check for spark jump...there was none. I started removing the spark plug wires one at a time with insulated pliers. I found they all had spark, it seemed to be good blue spark...I could see it jumping from the plug wire to the spark plug. However I could remove the top two wires on the port side and the middle wire from the starboard side all at the same time and there was no difference in the way the engine ran. It was clearly running on three cylinders. Any ideas???

Thank You,

Mitch...

[boats.net]

That is usually clogged carbs, there may still be trash in the fuel inlet of carb restricting fuel to float valves.

[mitch00]

Problem Fixed!!!

I found the problem. It was the top fuel pump. It had a 1 1/2 rip in the diaphram. I misunderstood the testing method for the fuel pumps and that’s why I missed it. Motor is running on all 6 now. Thank you for all of your advice!

Thanks,

Mitch...