Need Help with 1977 15 hp Johnson Looses Power Thanks

" Also have a question about

" Also have a question about a 77 15 hp johnson.
I have one,,,Its looses power when on the lake at 3/4 to wide open throttle,,,
I put it in neutral to clear it out,,,,then get a little further down the lake and the same thing happens again.. Then eventually it just runs at half its power. And wont clear up.

I've replaced both plugs,,,I found the bottom one fouled out,,,,Then I replaced both coils, cause of a crack, and someone suggested it...
But I still get the same problem,,
My vent is open on the tank,,, And its getting spark, When the prob acted up lastnite, I took one wire off at a time,,, and what a shock I got!!!
It doesnt smoke,,,,until it looses power and I clear it out,, then i get white smoke that goes away as it clears out.

Any help/ suggestions greatly appr....
Thanks again, Brian "

" Do the basics. Check compres

" Do the basics. Check compression (Blown head gasket) and check that you have a spark that will jump a gap of 3/8" or better.Laying plugs on the block is simply not a good test for spark.Thermostat in place and working properly? Fuel pump diaphragm rutured, causing a cylinder to flood? "

" Do the basics. Check compres

" Do the basics. Check compression (Blown head gasket) and check that you have a spark that will jump a gap of 3/8" or better.Laying plugs on the block is simply not a good test for spark.Thermostat in place and working properly? Fuel pump diaphragm ruptured, causing a cylinder to flood? "

" Thanks Sparky,,, Compression

" Thanks Sparky,,, Compression good, no big difference between cylinders,,, the spark was good,,,was using a snap on spark tester,,,both cylinders showing a nice blue spark,,,
While checking things out, I noticed sealant around the thermostat cover,,,I took it apart and the thermostat was all gummed up,,,I cleaned it and put it in a cup of hot water from the house,,it did'nt open,,So I boiled some water and put it in there,,,still did'nt open,,,Looks like it's a 143 degree t stat,,,Boiling water should of opend it,,,So gonna get a new one and give it a try. "

" After my first message, I to

" After my first message, I took the carb off and cleaned it out,,,did find gumming/ varnish in the idle passage,,,cleaned it out an reassemble..
Cleaned an blew out the fuel lines,,,Took the fuel pump apart,,did'nt see anything in there!
The tank is clean and nothing clogging the pick up screen.

What do you think on the thermostat?
Being stuck shut,,The Selco manual I have doesnt say what a stuck one will cause as far a performance. "

" Try the new thermostat, But

" Try the new thermostat, But if the old one was stuck do you think you may have damaged your motor from overheating?????????. Maintenance does not cost money ,in fact it saves money. "

" Na, don't think I damage

" Na, don't think I damaged it, it was running good last year,,, I bought the motor off someone I work with who upgraded to a bigger boat.
I'll get a new t stat for it though.
I believe I found the problem,, The engine had good spark like I told you before,, Well I pulled the head off to look inside and check it for being warped,,,it looked pretty good, put a straight edge across it and could'nt get a .001 feeler blade under it,,,So I cleaned stuff up an routed all the wiring nicely, and secured everything,,, Tried to fire it up, and it won't start,,anyway after rechecking my grounds and stuff,,,Started wiggling the harness and got intermittant spark,, off with the fly wheel and out with the stator,,,did an ohm check and found blk/wht wire and wht/blk wire were broken inside..
Gonna cut out the bad sections,, sodder and shrink wrap them,,,Guess from all the years of use, the insides of the wire just broke,,, I'll let you know how I make out with it,,,
I need this thing running by the weekend for a bass tournament in Yardley, Pa. 45 min outside of Philadelphia. Brian "

" Well all that hard work didn

" Well all that hard work didnt pay off,,,,,,still having the same problem "