Just picked up this motor off marketplace for around $300 with rigging and steering. Got it installed in my boat. At first it wouldn't start without spraying fuel mix into the carbs. Once started it seemed to run ok but would consistently be idling on 3 cylinders.
Compression test shows 120-125 across all 4 cylinders. I noticed the motor had a hodge podge of mismatched parts on it so I've replaced the following with genuine OEM parts:
4 spark plugs
4 ignition coils
4 coil wires
2 power packs
Rebuilt carbs with oem carb kits. Float is set to even with the bowl.
The motor will now start without spraying fuel into the carbs but I'm still having the same idling issues. Motor will idle normally for a few seconds and then it will bog down. It usually stays running on 3 cylinders but sometimes it dies. This seems notable because I feel like this motor should still idle on 3 cylinders. I can pull the wire off cylinder 4 with no change to engine performance at idle. With plug wire reinstalled I'm able to Rev freely through the rpm range without misfiring. I've tried to swap the new parts between cylinders to see if the problem moves but it appears to be isolated to cylinder 4. I've used a timing light to verify that I still have spark when it starts to bog at idle. When pulling plugs after running they all appear to be very similar. I was expecting to maybe find that #4 was fouled out but that's not the case. I inspected the reeds with a scope and they look to be in good shape.
Note that I'm not an outboard mechanic but I paid my way through college by turning wrenches so I'm pretty handy. I picked up the online seloc manual but to be honest it's not very useful. I'm in search of a better shop guide
Compression test shows 120-125 across all 4 cylinders. I noticed the motor had a hodge podge of mismatched parts on it so I've replaced the following with genuine OEM parts:
4 spark plugs
4 ignition coils
4 coil wires
2 power packs
Rebuilt carbs with oem carb kits. Float is set to even with the bowl.
The motor will now start without spraying fuel into the carbs but I'm still having the same idling issues. Motor will idle normally for a few seconds and then it will bog down. It usually stays running on 3 cylinders but sometimes it dies. This seems notable because I feel like this motor should still idle on 3 cylinders. I can pull the wire off cylinder 4 with no change to engine performance at idle. With plug wire reinstalled I'm able to Rev freely through the rpm range without misfiring. I've tried to swap the new parts between cylinders to see if the problem moves but it appears to be isolated to cylinder 4. I've used a timing light to verify that I still have spark when it starts to bog at idle. When pulling plugs after running they all appear to be very similar. I was expecting to maybe find that #4 was fouled out but that's not the case. I inspected the reeds with a scope and they look to be in good shape.
Note that I'm not an outboard mechanic but I paid my way through college by turning wrenches so I'm pretty handy. I picked up the online seloc manual but to be honest it's not very useful. I'm in search of a better shop guide