Johnson 48 1989 Stall after running and has no spark

I have an 1989 Johnson 48 special outboard motor. When I put the boat on the water the engine starts right away without any problems. I can then drive the boat around at any speed for about 15 to 20 minutes before the engine cuts off. After that I can not restart. When I check the spark, I am not getting anything. I am getting plenty of fuel and the engine temp is barely warm at best ( I can place my hand on the side of the engine and it feels luke warm). If I wait for about 30 minutes, I can usually get the motor running again but it hesitates a lot and stalls after a couple of minutes. When I get home, I check the spark and it seems like I have full spark again. I then can run the motor out of the water (hose hooked up to the water intake) for over an hour without any problems. I even run it in and out of gear. As soon as I put it back into the lake, the boat will only run for about 20 minutes.

What I am wondering is if there was something on the motor that would cause the spark plugs to stop firing.

Thanks for any help.

Re: Johnson 48 1989 Stall after running and has no spark

I'm stumped, lets see what the xperts think.

I'd take a guess at the powerpack failing when warm, it cools down and resets. But it doesn't repeat on the hose, very odd.