I have some problems with my motor and need/request for help.

1996 Johnson Fast Strike
Model # J150ELEDB
Serial# G04078037

Recently, I launched the boat and the motor ran fine. Mid-day, I idled out of a slough and gave it gas to get on plane but the motor stalled and died. could get it to idle but it was rough. I kept trying to get it cranked but when I engaged the gear, the motor died. I had to be towed back to the ramp. I tried to crank it again there but it would not crank. A day or so later, I removed the plugs, sprayed some yamaha fogger in each cylinder, and replaced the Champion plugs with NGKs. It cranked and ran fine with the flushers attached to a garden hose.

A few days after that, I topped the fuel tank off with fresh gas, some yamaha ring free and fuel conditioner. I took it back to the lake and, again, it ran great for 45 minutes or so. I returned back to the launch (in case it would not crank again so I would not have far to go to get it back on the trailer), turned off the ignition, and cranked it up again and blasted off. I did this several times and everything appeared to be working fine. Having some confidence, I headed to a local marina and topped it off with gas again to make sure I had enough to make a long run up the lake and back. AFter fueling, I idled back to the main lake body past the marker buoys and gave it the throttle. The motor stalled and died just like it had done a few weeks ago. I returned to the ramp under power of the trolling motor and trailered home.

Today, I attached the flushers and garden hose and it would not stay cranked. I pulled the spark plugs and sprayed each cylinder with fogger. I put the same NGK plugs back in and it cranked fine. I engaged the gear and ran it for about 5 minutes with no problems. I am concerned that if I get it back to the lake, it will run great for 45 minutes and then refuse to crank after I sit and fish for a while.

Some folks I have talked to suggest it is a weak or failing power pack. Others suggest that the oil mix is too high or rich. In any event, it seems odd to have it running great one minute and then have it refuse to run the next.

Any thoughts from (1) the experts or (2) those who have had similar experiences would be greatly appreciated.