Overheat and now will not start

[dave11998811]

I have a 79 100hp johnson and I took it to the lake about a week ago and it ran fine for about ten minutes. Then it overheated and shutoff. It will crank but will not fire. Took the lower unit off and found that the impeller was melted and some of the water pump housing was also melted. Can someone tell me what caused this and what I need to look for to repair it. When I try to start it now its almost like the battery is dead but has full charge. I dont know a lot about boat motors. Please help.

 

[Boobie]

Take the plugs out and try to do a compression test.

 

[dave11998811]

Compression is good

 

[OMG4.3IO]

Maybe ran it without water on it?

 

[dave11998811]

Water was coming out the pee hole normal then it stared to kinda trickle out. Then it was like a mist came out and then it shut down.

 

[still_bill]

Lower unit or WP has nothing to do with starting. Like suggested above - what are compression numbers?

My guess is failed to get oil in gas and stuck rings.

 

[dave11998811]

Had oil in the gas. The battery was bad. Now it tries to start and will start for a second or two then shut down.

 

[guyjg]

Like suggested above - what are compression numbers?

You overheated it...w/o good compression it won't start/run worth a crap. Scored cylinder walls from overheat,

 

[bill_w]

Water was coming out the pee hole normal then it stared to kinda trickle out. Then it was like a mist came out and then it shut down.

So you kept it running and let it self destruct. To melt the impeller housing you had to let it run for quite a while. You say the compression is good. Funny, you said the same thing about the battery, it was good, then a couple of days later it was bad.