Johnson 150 sudden loss of power

I have a 78 150 Johnson this past weekend I ran about 4-5 miles down river with no stops Motor ran great. On the return trip after 2 1/2 to 3 miles back up river the engine gradually slows down to idle speed with out me touching the throttle. It would never get over idle speed, I checked the primer bulb one and pumped it at one point the prime bulb stuck completely flat and then built pressure up. The Motor died several times and would crank back up, finally it would not crank. At one point I had the throttle all the way down and could not get more that idle speed. Any advice wull be helpful I don't have a clue. Also The Positive battery post was so hot it bunt my hand so there may be some kin of short???

Re: Johnson 150 sudden loss of power

If the bulb goes flat on you, it's either a lack of tank venting or you've got a clogged filter/screen/line somewhere between the bulb and the tank. Often the clogged line can be caused by an anti-siphon one-way valve that has stuck, these valves are found right on the fitting that enters the tank - replace or just knock the guts out of the current valve and replace.<br /><br />Jon

Re: Johnson 150 sudden loss of power

it could be possibly overheating, check to make sure you have water coming out of the tell tale

Re: Johnson 150 sudden loss of power

I forgot to add the fact that when I checked the battery cables that the positive side was so hot that it burnt my hand causin blistering. See original edited post. Thanks for the help.