78/ 70 johnson no power under load

[trottsmart]

can anyone help me please. I have a 70 johnson that i bought from a guy who ripped me of but anyway the boat has no power under load. I can get the boat going more then 10 knots max. I checked the compresion and all 3 were at 100 or so. I checked my ball to see if it was getting soft, it did get somewhat soft. I opened my gas cap and that didnt help. Does anyone have any ideas that I can check next. The motor idels fine. thanks

 

[jriegle04]

Re: 78/ 70 johnson no power under load

check spark and rebuild carbs. carb kits are cheap and spark test is free until you find the problem. i would also check flywheel magnets for loose or broken magnets.

 

[kenmyfam]

Re: 78/ 70 johnson no power under load

Start with a basic health check of the motor.
Compression, Spark, Fuel delivery, Spark plug condition and go from there.
If the motor is an unknown quantity to you as well then you should really change the impeller.

 

[gizzyknows]

Re: 78/ 70 johnson no power under load

Does the motor sound like you should be going fast?Also can you trim up and make sure (safely) that the prop is not just sitting thier and not spinning like it should?

 

[tashasdaddy]

Re: 78/ 70 johnson no power under load

read ethanol and carb cleaning. then check timing, and do a link n sinc. having lots of problems with that vintage 3 cylinders do to it. http://forums.iboats.com/showthread.php?t=299680