95 Johnson 15hp 2 stroke. Stopped suddenly at full speed and hasn't started since.

Had this motor for about a year, never any issues, ran good/reliable. Briefly, the other day, someone fell overboard (14' v-hull jon boat.) The boat really jerked and twisted, the boat got very perpendicular. Good amount of water in the boat. Got everyone back onboard. Had issues starting it. Finally got it started with it trimmed up a bit. Got us back to shore. The next morning, bilged water and after about 3-4 attempts (not unusual when cold) it started fine. Ran it for a minute or two.

Later that day, ran it full throttle for about 20 minutes, did some turns. On the way back, the engine died (almost like it ran out of gas), it was pissin and nothing sounded or felt weird. Haven't been able to get it to start since.

I've drained the carb via the drain plug. Replaced all gas/oil. Carb cleaned via the drain plug opening and the fuel pump line into the pump, all around that void, and into the feed line from pump to carb. Ran some new gas/oil through the pump and carb and let it drain to get any remaining water out. New spark plugs.

No idea where to check next. Not sure what could have happened. I thought maybe that river water had gotten into the fuel tank when boat got tweeked. But not entirely sure of what happened. Could the outboard gotten jerked enough to damage the gearbox down the prop? The way it was running fine, and then stopped pointed to a fuel issue to me but unsure now. Tomorrow will disconnect the kill switch to isolate that, but that was working when I ran it first time the next morning.

Any insight would be greatly appreciated. This engine doesn't seem too complicated, but I don't want to rip it apart. The carburetor has many little pieces!

Does the engine appear to have normal compression... and no traces of water in the cylinders or on the spark plugs?

With spark plugs removed, the spark should jump a 7/16" gap at cranking speed... does it?

Note that the 7/16" gap is important.... checking spark by using the spark plugs is a waste of time!

joereeves said:

Does the engine appear to have normal compression... and no traces of water in the cylinders or on the spark plugs?

With spark plugs removed, the spark should jump a 7/16" gap at cranking speed... does it?

Note that the 7/16" gap is important.... checking spark by using the spark plugs is a waste of time!

Click to expand...

Thanks for the feedback! I am a year into owning a boat, and this is the first trouble I've encountered. I do have good spark. Unfortunately, with a compression gauge, there is no compression on either top or bottom. It is a fly-wheel start, I pull around 8 times. Even with choke on and full throttle, nothing. There is a faint air release when I reset the gauge, but doesn't go above 0.

Another forum someone mentioned possibly a bad power pack? But no compression seems like a bigger, more serious issue. Unless I'm doing something wrong. Both plugs out, coil cables unplugged from plug. Try starting motor and gauge on each cylinder. No water comes out with sparks unplugged and pulling flywheel. So there can't be a ton of water in cylinders.

I get gas through to the carb drain plug when priming so it isn't fuel starved. Any ideas on next steps? Already touched base with a needle in a haystack Johnson mechanic in the area.

If you have zero problem on both cylinders, in all probability the head gasket has blown between the cylinders... in which case (usually) compression from one cylinder is escaping into the other cylinder. Remove the cylinder head in order to inspect the gasket and the head/block sealing surfaces.

Note... stating that you have good spark means nothing to a technician... you either have spark that jumps a 7/16" gap or you do not. Some boaters have told us that they have good spark as they get a shock when holding onto the plug boot.