1976 Johnson 55HP Carb Jet

[will941s]

Posting to ask if I can install the 1977 fixed idle jets on a 1976 Johnson 55hp with the settable idles jets in my carbs? Or is there something different between the two carbs besides the jets. Hopin this will eleminate alot of little issues. Thanks for your time

 

[Daviet]

Re: 1976 Johnson 55HP Carb Jet

Usually people want to go the other way to get rid of the fixed jets so they can fine tune the carbs.
By quickly looking at the parts breakdowns of the carbs, the body number is different, but that doesn't mean it can't be done.
Have you thought about swapping complete carbs?

 

[will941s]

Re: 1976 Johnson 55HP Carb Jet

I'm pretty sure I can get my hands on a used set with the fixed jets. Just thinking of adjusting timing versus adjusting timing and carbs during service intervals.

I got this 1976 Johnson 55 a month ago with EVERYTHING original. I oiled the cylinders and let it sit. Replaced the fuel lines, fuel pump, water pump, plugs and lower unit oil. Then test ran it in a tank for about 2 hours, checked compression and it's 150 psi even...and still is.....purred like a kitten. I changed the lower unit oil again and tested it on the river. Ran great, but now the idle seems out of whack. Runs like a clock at mid-full throttle, but idle is crazy. If it sits, its hard to start. Sometimes will slowly die (at idle only)...then hard to start. Hit the gas and every once in a while it'll bog then take off....or die. What do you think of all this? Should I zero it out and re-sync it? Clean the carbs?

 

[Daviet]

Re: 1976 Johnson 55HP Carb Jet

If the engine has been sitting for a while you might need to overhaul the carbs and clean them up. Have you checked the plugs, are they in good shape and gapped properly? Have you gone through the carb adjustments to make sure they are set correctly?
Once you get everything adjusted properly, there shouldn't be any need to readjust every thing.

 

[will941s]

Re: 1976 Johnson 55HP Carb Jet

Plugs are brand new and gapped properly. I am actually going outside right now to pull the carbs and clean them. I'm kind of interested in seeing the inside of them, since they may never have been cleaned. After I do that I am going to check the timing to make sure it's between 2 &4 degrees at idle and check all the linkages to make sure they are right. I think initial adjustment of the carbs are 1 5/8th out from seated....is this correct?

 

[Daviet]

Re: 1976 Johnson 55HP Carb Jet

I usually start with the needle opened up 1 1/4 turn out.
Make sure to remove the core plug on top of the carb and clean the passages in there real good. Remove the high speed orifice and clean all passages and blow out with compressed air.

 

[will941s]

Re: 1976 Johnson 55HP Carb Jet

Thanks for all the help. Heres a update on the motor, I pulled the carbs and cleaned them.....everything that could be cleaned has been cleaned. The bottom carb was pretty bad, the High Speed Main Jet was pretty much blocked in. Had to scrape the crud away the even get to it to clean it. Top carb was pretty much spotless.

Re-installed the carbs, hooked everything back up and started the motor. It was still a little hard to start from cold, but once it got warm I checked the timing. It was set right at TDC, so I adjusted it to 4 Degrees BTDC like the manual says. Then re-adjusted all the linkages to take the slack out. Last I made sure the carb roller was touching the cam...with the butterfly valves all the way closed.

It ran well, but when you put it in gear it sounded like it was barely idling...like about to cut off. I let it run like that til it did. I let it sit for about 30 minutes and to get it to start I had to hit the choke...get it to fire...then give it gas with the warm up lever to get it run...at that point it would die even at idle not in gear.

I adjusted the carbs about 1/16th turn richer than what they were set at when I took them apart, the motor seems to idle better, and the RPM's barely drop now when put in gear. Itll idle forever at dead idle right now. I just let it sit for about 20 minutes, went back out, hit the key and it started right up.

If I had to assume, I would think it was combination of dirty carbs, bad timing and lean carbs......does this sound right?

 

[Daviet]

Re: 1976 Johnson 55HP Carb Jet

I would think you are correct, glad you got it running. What did you set the idle at, 700-750 warmed up and in gear with the boat in the water?

 

[will941s]

Re: 1976 Johnson 55HP Carb Jet

Well, as close to in the water as I could get...my 55 gallon drum. Idle in gear and warmed up is a little over 700 RPM's. For the rest of the night it was starting as soon as I hit the key at about 30 minute intervals. Before the adjustment if I waited 30 minutes I would have to do the choke/Throttle thing to get it to start. Planning on filling the drum back up in the morning and seeing how it does from cold start through the warm up stage. Hopefully everything is right on the money, however i'm thinking a little more fine tuning may be in order, esp since I tuned it with a flashlight in the dark. Will keep posted on what happens tomorrow.

 

[will941s]

Re: 1976 Johnson 55HP Carb Jet

Went out this morning, hit the choke and it started right up. I let it run for about 30 minutes and put it through the gears,never seemes like it was going to cut off like before. Throughout the day I went out and started it...every time I did, it started right up. As of right now...i'd say problem solved. I pulled the drum out from under the motor and put the boat back in the back yard. Thanks for al the help...and I hope this thread can help someone in the future.

 

[Daviet]

Re: 1976 Johnson 55HP Carb Jet

Glad you got it running, hope you have a lot of fun with it.