Engine not wanting to run - 1978 Johnson 115

I have a Johnson 115 engine on my bass boat. We took it out for the first time this past weekend after winter storage. The day prior to putting it on the water I hooked it up and let it run for about a half hour to 45 minutes. It ran great. I filled the tank and headed to the lake. Initially it started and idled fine but when I was out of the no wake area and throttled it up it bagan to sputter and eventually died and would not start again.....took it home and and added a fuel conditioner and on the hose it ran great. The next day I put it back in the water. It would throttle up but it wasn't getting the thrust it normally has. At 1500 - 2000 rpm's it would bearly move but it never cut off as it did the day before.

Inherited boat from Uncle.....first time owner. Any suggestions are welcome.

Thanks,
Mike

Re: Engine not wanting to run - 1978 Johnson 115

Check for spark on all 4 plugs. That engine will run just fine on 2 or 3 cyls when running on the garden hose on the trailer. You need all 4 cyls firing when it's in gear and the prop exhaust is buried under 12" of water. Weak ignition components tend to work ok when the engine is cold. Also, can fail once the engine heats up to normal operating temps.