Help with 140hp 1981 Johnson - won't go full throttle

[Moparkat]

Okay so my boat is a work in progress and progress is slow. 1974 18ft Fiberform trihull openbow.
Issue
When out in the water it just won't go full throttle but the shifter is all the way down. Hubby adjusted the idle too high but otherwise we haven't done much other then replace the impeller.
Also does not shift smoothly into nuetral.
What can we look at to get this working?
Thanks

 

[ezmobee]

Re: Help with 140hp 1981 Johnson - won't go full throttle

Might have a cylinder not firing. Had one go on my friend's 90 (plug wire) and it started, ran, and sounded fine but just had no power.

 

[fshrgy99]

Re: Help with 140hp 1981 Johnson - won't go full throttle

High idle will cause it to shift with difficulty. Why was the idle turned up? The throttle and shift cables may need adjusting.

 

[emdsapmgr]

Re: Help with 140hp 1981 Johnson - won't go full throttle

You may not have the throttle cable adjusted properly. Take the airbox cover off the carbs. Move the throttle handle to the full forward position. Visually check to see that the carb butterflys have rotated to the level (full throttle open) position. If they are not level, you will not get full throttle. It is possible to adjust them so that they overrotate and begin to close again. As was mentioned, a throttle cable adjustment problem can also make it hard to shift in and out of gear and be a cause for high idle.

 

[jc turtle]

Re: Help with 140hp 1981 Johnson - won't go full throttle

My son has the same motor, with the same problem. It turned out that 2 of the coils were bad.
After I changed the coils, for the first time since we owned it, the boat scooted like a rabbit on fire! It was scary fast! You may have the same problem, it would sound great at idle, but would not get above 3000 rpms. Check it out, John

 

[Moparkat]

Re: Help with 140hp 1981 Johnson - won't go full throttle

You know one of the coils has a crack in it. Just noticed it. Will be headed out for new parts and many thanks for the incouraging solutions.
Hubby turned up idle and didn't know what the results would be. I have no idea why.