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Forwards throttle not fully engaging - any ideas? Johnson 55hp 1979

jasondainter

jasondainter

Regular Contributor
Hi All.

Have a Johnson 1979 55HP, as some of you know (and have been helping me tremendously!) i dissasembled the entire lower unit, cleaned everything up and reassembled, initially it was to fix the reverse gear but I ended up giving it a well needed rebuild.

Im sat in the boat now on the water, good news is reverse works fine, but when I engage forwards throttle it reaches about 7-8 knots then it suddenly slows down thr more i push on forwrards. I filmed it here below in the video.

Im going to spend the next few hours trying to figure out what this is, any ideas? Hoping its just an easy adjustment somewhere.

 
Look at the butterflies in the carbs and make sure they are opening correctly. Make sure both carbs are opening. Make sure the cables are on correctly.
 
flyingscott said:
Look at the butterflies in the carbs and make sure they are opening correctly. Make sure both carbs are opening. Make sure the cables are on correctly.
Click to expand...

I forgot to say I also took off both carbs and cleaned them, reassembled. They opened fine when I put them on any idea how I would check that with boat still in water?

re: cables which cables did you mean?

thanks !
 
Hi Again.

I was going to post this in a new post later on, but now I'm wondering if this is related. When I fired this up (drove about for maybe 30 mins max) I noticed all these black exhaust marks on the outside of exhaust area. I just repainted the engine so its pretty noticeable here. I dont recall the boat producing that much soot before I repainted it either. Seems like a lot for just 30 mins of driving on a fresh paint job?

36N0Obd.png


Since everything with the throttle worked perfectly fine before I disassembled (reaching about 23 knots top speed) I'm pretty sure this something misaligned that needs adjusting or something that I missed when putting things back together.

Can someone kindly talk me through some steps involved in how I can diagnose what I might have done wrong whilst still on the water (it was a bit of a mission getting it in so I'd love to avoid taking it out again until I need to).

Is it OK and safe to take off the plastic silencer box from the front of the two carbs to get a better look at if they're opening properly or not when I go full throttle (unless I'm missing a trick I can only do that whilst actually moving forwards so it makes it bit hard to diagnose but I can bring my girlfriend along to test!).

Thanks ahead. Really hope this is something simple. Seems I just replaced one problem (reverse gear, which works a dream now) with another big headache :-(
 
Last edited:
Finally got to fixing this for this season before it goes in the water here in Sweden.

Quite a few people told me I need to do a "link and sync" I have the original manual so following this.

I dont have a timing light or test flywheel of any sort, how big a problem is that going to be when doing this?

Any tips to consider on doing a link and sync from anyone who has done one on this engine?
 
You are probably going to need to get a timing light. They aren't that expensive.
Also, did you clean out the jets in the bottom of your carbs? Sounds like your high speed jet could be clogged. Or you could have an air leak in your fuel system. Leak in hoses or warped carb bowls.
I would also double check my throttle cable connection at the motor.Does it move freely through its entire range?
 
jasondainter said:
video of issue here (sorry about the wind noise!)

Click to expand...

Hey, did you ever get to the bottom of this?

Also does it rev up fully in reverse?

I'm having the same issue with a 70hp runs sweet but in forward gear its as if it's hitting a limiter. But I seems to rev up fully in reverse no problems or hesitation at all.

Thanks Brian
 
Hi Brian.

I did not yet fix but I'm in the process of doing a link and sync see the manual for the right settings there.

https://www.youtube.com/watch?v=H6lHx4xIKZA and https://www.youtube.com/watch?v=uZ9GQ9lNCHE&t=0s are helpful with this.

I did notice that my butterflies on the carbs were not opening correctly (should be totally straight open not too far, not too little) when at WOT.

Its taking some fiddling to get the link and sync set up but hopefully this will work.
 
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