1976 Johnson 70hp problems

[Mach1Boater]

I have a 1976 Johnson 70 on a 16ft Eagle boat. The motor starts and runs great in the driveway but once i put her in the water she wont advance when i give it throttle. I have cleaned and rebuilt the carbs, it has great compression and I have changed the coils and power pack. I have a ignition advance switch I am going to put on it next to see if that helps. does anyone have any ideas if that dont fix it?

 

[hogg]

Re: 1976 Johnson 70hp problems

What does it do when it wont throttle up?
Cough, Spit, die, what?

 

[Mach1Boater]

Re: 1976 Johnson 70hp problems

it just sounds like its getting fuel just got advancing. every once in awhile it will shut off but will restart.

 

[Bosunsmate]

Re: 1976 Johnson 70hp problems

Have you checked timing?
A broken flywheel key could throw your timing out

 

[fireman57]

Re: 1976 Johnson 70hp problems

Check the welch plugs on the carbs to see if they have X's on them. There is a service bulletin number 1144 on this engine for the carbs. If there is no X on them I suggest you check this out. You can do a search for it at the top of the page. Fixed mine.

 

[Mach1Boater]

Re: 1976 Johnson 70hp problems

ok i will check that stuff. I know I need to change the advance switch I will look at the fly wheel key tonight when i pull it off. when i got the motor they said that the carb needed cleaned thats it. but i think its a lot more.

 

[Mgoul346]

Re: 1976 Johnson 70hp problems

I have a 1976 johnson 70 hp. I recently replaced two fuel lines that prevented it frpm starting and it ran for a few days. Now it will not run. I try to start and it wants to start and then stops. I had a friend pull the spark plugs and he noticed alot of fuel on the plugs. There is also fuel leaking from the exhaust just trying to figure out where the problem is so i can get back on the lake.

 

[Daviet]

Re: 1976 Johnson 70hp problems

Mgoul346, you should start your own thread so you don't get lost.
Have you checked spark, will it jump a 7/16" air gap and is it bright blue?
What about compression, what are your numbers?

 

[mrcj001]

Re: 1976 Johnson 70hp problems

Check to see if the manual choke is in the proper position...(Automatic or Off) I kinda had the same symptoms and noticed my manual choke was in the "ON" position...it will run, but run like crap the run good then run like crap. I think putting on the engine cover, I must have pushed the lever down to the "ON " position.......... switched it to auto and seems to idle are run 100 times better.

Also, those small fuel lines that feed the carbs, make sure they are air tight. If you remove them by pulling them off and re-using the old zip ties, you are probably loosing vacuum there. Be sure to use zip ties for fuel line.