1987 Evinrude 150 V6 VRO E150STLCUR. Ok people. Oilmix system gone before I got the boat...so i premix. Boat starts fine and idles fine. Runs strong to up on plane. Gets on plane fast as it always has. At about 2500 rpms it cuts out and surges rpms up and down. Have read a bunch and performed a few tests so here goes...
Compression test is either 85 to 90psi on all cylinders. It is NOT fuel related. Checked, rechecked and changed everything on fuel side. Cleaned carbs, fuel pumps removed and inspected (look pretty freshly rebuilt), new fuel lines, water seperator has new filter and NO water present, bulb is new, tank is clean, etc. Finally put a fuel pressure guage on it. 4 to 7 lbs depending on rpms. All is good. I KNOW its not fuel. Did spark gap test by simply turing motor over with starter and it fires blue across 7/16" gap. Not surprised seeing how it idles fine and runs strong up to about 2500rpms. So i took it out yesterday with a timing light and here is what happened. Starboard bank (all three cylinders) fire consistent according to watching timing light while running. Even when it starts the surging the firing is the same and consistent ON THE STARBOARD SIDE. The Port side bank (all three cylinders) fire consistant according to timing light up until it starts to surge rpms up and down. When the surging starts the fire is weak looking (timing light fires dimmer) and the firing seems erratic looking.
I have read enough to get REALLY confused on what I should do next. If I switch power paks around and the starboard bank screws up can i assume it is the power pack? If I switch the paks and it stays on the port side is it possible the stator? Or something else? Something else I can test? I have a digital multi meter but not all the "outboard" testing tools I probably need. Any help? Thanks in advance.
Compression test is either 85 to 90psi on all cylinders. It is NOT fuel related. Checked, rechecked and changed everything on fuel side. Cleaned carbs, fuel pumps removed and inspected (look pretty freshly rebuilt), new fuel lines, water seperator has new filter and NO water present, bulb is new, tank is clean, etc. Finally put a fuel pressure guage on it. 4 to 7 lbs depending on rpms. All is good. I KNOW its not fuel. Did spark gap test by simply turing motor over with starter and it fires blue across 7/16" gap. Not surprised seeing how it idles fine and runs strong up to about 2500rpms. So i took it out yesterday with a timing light and here is what happened. Starboard bank (all three cylinders) fire consistent according to watching timing light while running. Even when it starts the surging the firing is the same and consistent ON THE STARBOARD SIDE. The Port side bank (all three cylinders) fire consistant according to timing light up until it starts to surge rpms up and down. When the surging starts the fire is weak looking (timing light fires dimmer) and the firing seems erratic looking.
I have read enough to get REALLY confused on what I should do next. If I switch power paks around and the starboard bank screws up can i assume it is the power pack? If I switch the paks and it stays on the port side is it possible the stator? Or something else? Something else I can test? I have a digital multi meter but not all the "outboard" testing tools I probably need. Any help? Thanks in advance.