My motor ran great for many years with simple maintenance. I scored a cylinder and rebuilt the motor. I've never been able to get the motor to run as good as pre-rebuild.
The motor runs okay above 1200 RPM, but I can't get it to idle below 900 in gear for very long without a sneeze and stall.
I performed the following.
Bored .020 over and replaced all 6 pistons and rings.
Replaced all bearings.
Replaced all seals.
Rebuilt the lower unit and water pump.
Replaced all 6 coils.
Replaced the trigger coil.
Replaced the power pack.
Rebuilt all 6 carbs.
Replaced spark plugs with QL76JC4 @ .030
Replaced the carb to manifold fuel lines.
Inspected the flywheel magnets.
Replaced VRO pump and continue to use the oil injection feature.
Check and recheck the compression.
Sync and linked per the OEM shop manual many times over.
Set the max timing at 18 BTDC with the boat in the water
Checked low oil alarms
Checked fuel vacuum switch
Checked overheat switch.
Checked the shift switch.
Checked that the proper idle air jets are in the correct locations.
Here is what I've checked most recently:
Pulled the carbs and throttle plate and checked for crud. None was found. No clogged anything. Put a fender washer on the middle screw of the idle jet cover to make sure there isn't air leaks.
Ran the engine on the hose and use the IR thermometer and see all spark plugs reading about 130 degrees F.
Timing light shows a steady timing mark on number one. It's not missing or erratic.
Checked compression and find all cylinders read from 99-108 PSI with the throttle held open.
I just ran the engine about 10 hours over the weekend with a combination of trolling as slow and I can with a few stalls and some limited mid range planing speeds up to about 4000 RPM. I filled the nearly empty tank with fresh 87 gas and some sea foam additive. I checked the new spark plugs and they are very wet and the insulators are still white as new. The engine seems to use enough oil. I get plenty of blue smoke at startup and can see it while trolling. Seems to me the white insulator color is a little weird. I would have expected the usual cardboard color. Is the sea foam keeping the plugs from reading correctly?
I'd like to get the engine to run at the factory spec of 650-750 in gear and get rid of the sneeze and stall. I've got the idle timing screw almost set to the last threads which I know is not right but that's the only way it runs at idle speeds of about a 1000 RPM in neutral. If I back the idle timing screw in to about the middle portion of the threads the motor runs on the hose, but not in the water with the additional exhaust pressure. The timing light shows around 0-2 when idling at 1000 RPM. I can back it down to 4 ish but then the stalling is horrible. When the motor stalls the fuel primer bulb is still firm so I think the pump is working properly.
Thanks in advance for your suggestions.
The motor runs okay above 1200 RPM, but I can't get it to idle below 900 in gear for very long without a sneeze and stall.
I performed the following.
Bored .020 over and replaced all 6 pistons and rings.
Replaced all bearings.
Replaced all seals.
Rebuilt the lower unit and water pump.
Replaced all 6 coils.
Replaced the trigger coil.
Replaced the power pack.
Rebuilt all 6 carbs.
Replaced spark plugs with QL76JC4 @ .030
Replaced the carb to manifold fuel lines.
Inspected the flywheel magnets.
Replaced VRO pump and continue to use the oil injection feature.
Check and recheck the compression.
Sync and linked per the OEM shop manual many times over.
Set the max timing at 18 BTDC with the boat in the water
Checked low oil alarms
Checked fuel vacuum switch
Checked overheat switch.
Checked the shift switch.
Checked that the proper idle air jets are in the correct locations.
Here is what I've checked most recently:
Pulled the carbs and throttle plate and checked for crud. None was found. No clogged anything. Put a fender washer on the middle screw of the idle jet cover to make sure there isn't air leaks.
Ran the engine on the hose and use the IR thermometer and see all spark plugs reading about 130 degrees F.
Timing light shows a steady timing mark on number one. It's not missing or erratic.
Checked compression and find all cylinders read from 99-108 PSI with the throttle held open.
I just ran the engine about 10 hours over the weekend with a combination of trolling as slow and I can with a few stalls and some limited mid range planing speeds up to about 4000 RPM. I filled the nearly empty tank with fresh 87 gas and some sea foam additive. I checked the new spark plugs and they are very wet and the insulators are still white as new. The engine seems to use enough oil. I get plenty of blue smoke at startup and can see it while trolling. Seems to me the white insulator color is a little weird. I would have expected the usual cardboard color. Is the sea foam keeping the plugs from reading correctly?
I'd like to get the engine to run at the factory spec of 650-750 in gear and get rid of the sneeze and stall. I've got the idle timing screw almost set to the last threads which I know is not right but that's the only way it runs at idle speeds of about a 1000 RPM in neutral. If I back the idle timing screw in to about the middle portion of the threads the motor runs on the hose, but not in the water with the additional exhaust pressure. The timing light shows around 0-2 when idling at 1000 RPM. I can back it down to 4 ish but then the stalling is horrible. When the motor stalls the fuel primer bulb is still firm so I think the pump is working properly.
Thanks in advance for your suggestions.
