79 johnson outboard has no power

[roadsterdt]

I have a 1979 johnson 35 that starts and idles great. The problem is when I accelerate (out of the water) it revs up but won't sustain the rpms and just falls back to close to an idle. I have changed the plugs, rebuilt the carb, changed to fresh gas, pulled the fuel hose off the carb and cranked it with spirts of fuel which appear normal, pumped the bulb during acceleration with no affect, used a spark checker on both cylinders and they have a big blue spark, compression is 125 in both cylinders. Any thoughts on what to try next?

[boats.net]

Check your reed valves, the reeds can cause different symptoms.

[Rebel Sympathy]

Originally Posted by roadsterdt

I have a 1979 johnson 35 that starts and idles great. The problem is when I accelerate (out of the water) it revs up but won't sustain the rpms and just falls back to close to an idle. I have changed the plugs, rebuilt the carb, changed to fresh gas, pulled the fuel hose off the carb and cranked it with spirts of fuel which appear normal, pumped the bulb during acceleration with no affect, used a spark checker on both cylinders and they have a big blue spark, compression is 125 in both cylinders. Any thoughts on what to try next?

If you want to remove the cover from your motor to check some symptoms, you can do so. But, be careful of that whirling flywheel - especially if you have long hair. It can grab your wig and scalp you. Also, be careful of arms, hands and fingers.
First of all, check or replace the fuel pump. One indication of a bad fuel pump is, when you take it loose from the motor, if there is wet (gas) on the back mounting gasket of the fuel pump, then the diaphram is broken and the pump is bad.
Take off with the throttle wide open. Is the magneto plate advancing and staying advanced? If not, check linkage.
Watch the carburetor. Is it spitting back through the carb? Could be a bad reed valve, or a leaned out situation in one or both cylinders.
Good luck.