more 15hp Johnson problems

[teamAssassin]

Alright. 1976 15hp Johnson running on a 10ft Zodiac. Rebuilt the carb, engine starts and runs great.....for about 5 minutes. Then it starts to sputter and stall out. Once I idle it down for a few minutes it will slowly climb back up in revs, sputtering the whole time. Once the boat is on plane it seems to clear up, but only for about 5 minutes. Then I have to repeat the above, idle down and such.
1. I didn\\\'t get a chance to feel the primer bulb while running, will check that next time.
2. Fuel tank is vented.
3. Engine is not hot at any time. Inspected water pump impeller and gaskets previously, all are in good shape.
4. How do I test the coils?
Thanks in advance for any and all help or tips given!!

 

[Blade_Link]

Re: more 15hp Johnson problems

to test the coils get yourself a voltage meter and place the place wire on the ground and the red in the spark wire and read the voltage.

it sounds like you might be running a bit lean/ or rich, try ajusting the mix 1/8th of a turn at a time either way

 

[tashasdaddy]

Re: more 15hp Johnson problems

read carb cleaning, adjusting, compression, coils. http://forums.iboats.com/showthread.php?t=299680