1980 johnson 100hp outboard will not accelerate past 2000 rpm

I recently purchased a used 1980 johnson javelin 100hp motor to repower my 19' mirrocraft. I got it off of craigslist after checking with the marina that inspected and it gave it the ok. I was told the motor had been in storage and only has six hours of use on it. After installing and testing it on my boat I found it would not accelerate over 2000rpm under load in the lake (on the hose it revs up fine). I did a compression test and got about 115 on all four cylinders and also had spark on all cylinders. I put it back in the lake and experimented with moving the throttle linkage by hand as well as advancing the timing by hand and got the motor to jump up to 3000 rpm and show signs of better performance. However, I broke the small plastic clip that holds the timing linkage on the arm coming out from under the flywheel. At that point I brought the boat to the local marina for them to inspect. I got the boat back after a month and there's absolutely no difference so I brought it back to them. They plan to test more but seem to of come to the conclusion that it has a bad set of piston rings which are keeping it from forming a strong vacuum and sucking fuel into the cylinders. due to my experience with advancing the timing by hand and getting better performance that way I feel as if its an electrical issue and would really appreciate any advice or a second opinion before I start rebuilding a motor which supposedly only has six hours of use on it. Thanks

Re: 1980 johnson 100hp outboard will not accelerate past 2000 rpm

you can follow the test below in my sig...make sure you fix/reset the linkage.

Re: 1980 johnson 100hp outboard will not accelerate past 2000 rpm

- 115 compression all around ----->piston rings probably ok
- only 6 hrs on the motor and been in storage ------> probably fuel supply related from carbs
- there is an o-ring on the crank that seals the crankcase so the piston moving down can force fuel air mixture into the cylinder ---> maybe.... but with only 6 hrs on the engine.....??????

I would suspect carbs or timing and link adjustments.

If you disconnect the throttle cable from the bottom of the throttle lever on the motor, you should be able to move the throttle lever by hand. As you move the throttle lever toward the full throttle position, the timing advance lever (attached to the top of the throttle lever) should move along with the throttle lever until the timing advance lever reaches its full-advance stop. You should then be able to push the throttle lever further to the full throttle position. The timing advance lever remains at its full-advance stop until the throttle lever is returned. Ensure that is all happening smoothly without binding.

Re: 1980 johnson 100hp outboard will not accelerate past 2000 rpm

Its been almost two weeks since I last posted here and the marina still has my boat. This weekend will be it, regardless of it they fix it or not I'm getting it out! Does anyone know if this 1980 100hp motor could have the S.L.O.W. mode safety feature built into it that I was reading about on the CDI Electronics Troubleshooting page? It's the first topic they discuss about evinrude johnson motors that don't rev over 2500 rpm. At least it would give me a good place to start before I take the carbs apart. Thanks for the help and advice!!

Re: 1980 johnson 100hp outboard will not accelerate past 2000 rpm

The slow feature was not available when your engine came out. You've gotten some good advice from the others. Unikely the engine needs an overhaul with 115 lbs compression. Based on the overhaul recommendation from that marina, I'd definitely get it out of there pronto. More likely a sync and link adjustment or a carb issue. Could even be a cable adjustment issue: make sure the throttle handle actually opens the carb butterflys fully when the throttle handle is in full forward position. You may have to pull the airbox cover off to actually see if the carb butterflys fully open for yourself.

Re: 1980 johnson 100hp outboard will not accelerate past 2000 rpm

Thanks for the help, emdsapmgr. The boats getting picked up today after I leave work and I plan to check it over from start to finish going down all the items people on here have recommended. Normally I do all my repair work myself but this is my first boat engine and I was hoping to just pay someone to fix my problem for a change so I could simple get in and go rather than have another project, but clearly some people who are supposed to be qualified for these things simply are not. Appreciate all the tips i've recieved here though!

Re: 1980 johnson 100hp outboard will not accelerate past 2000 rpm

got the boat back from the marina today after they completely lied to me, told me they tested it in the water and couldnt figure out what was wrong with it. Although the six inches of grass that was perfectly growing straight up in front of the tires didn't show any evidence of the trailer moving in over two weeks. Anyways, took it home and removed the air box as advised and noticed at full throttle the carb butterflys were only 3/4 open. I adjusted the stopper bolt for the throttle linkage, tightened the throttle cable lake tested it and success!!! The boat ran excellent!!

Thanks for all the helpful tips everyone, its nice to see that there are still people out there who have a clue what they are talking about!