1980 Johnson 70hp Seahorse

[cakopernik]

Hello. Im new to the forum. I have this 1980 Johnson 70 and it has not been on the water in a year. I took it out yesterday and when I got about 1/2 throttle, it started to jerk real bad. Felt like it was going in and out of gear. It got so bad that I put it in forward gear with no throttle and it would jerk. I had to use my trolling motor to get back to the ramp. Neighbor said he had the same issue and had to have new topend. I checked my compression and it was around 120 and 130 psi on all 3 cylinders. Plugs look great. Any thouhghts??????????

 

[rolmops]

Re: 1980 Johnson 70hp Seahorse

Welcome.
For starters,make sure that your remote cables move freely and check that they are connected and properly adjusted.
From there continue by checking all the shift rod connections.
Did you check lower unit oil?
Do these things to begin with.If all these check out correct,it is time to check the clutch dog.
In order to make this an easy job,do buy a manifacturer's manual for your engine.they are available in the iboats marine store.(the button in the upper left corner)

 

[cdoliver]

Re: 1980 Johnson 70hp Seahorse

start with cleaning the carbs.

 

[cakopernik]

Re: 1980 Johnson 70hp Seahorse

I cleaned the carbs out yesterday and installed new plugs thinking that was the issue. Ran better on the motor but no improvements on moving. I went by Barnes and Noble this evening and ordered the book. Linkage is new and the cables are working great and freely. I drained the oil and it was only about 1 quart or less that came out and it was black. I can get all the parts out until I get to the drive shaft and the prop hub. Then im lost. Drive shaft will not come out and have no clue on how to remove the bearing hub. thats why I ordered the book. Im guessing I need a speacial puller to get the hub out.

 

[rolmops]

Re: 1980 Johnson 70hp Seahorse

Let's stick to the simple stuff first.
Chances are that your shift rod connection (the one right under the engine) is loose ,or stuck in position.

 

[cakopernik]

Re: 1980 Johnson 70hp Seahorse

I just put the new shift rod linkage on Friday. Everything there is tight. Yesterday I got it about 1/4 throttle and it started to bang and jerk. Came home and replaced plugs and cleaned carbs. Went back out and did same thing. On way back to ramp, I put in forward gear and with no throttle, bang and jerk. Had to use trolling motor to get back to ramp. No bang and jerk in reverse. Just forward.

 

[rolmops]

Re: 1980 Johnson 70hp Seahorse

Looks like we are getting closer to the problem.
Try to adjust the shift cable so it pulls the shifter a bit deeper into the forward gear.The only change you made is the shift, so a bit of adjustment is probably what you need.

 

[cakopernik]

Re: 1980 Johnson 70hp Seahorse

I did try adjusting the cable so that the only gear I had was forward and it still did the same problem. I am also wondering if the cable is stretched to the point of no good. I am thinking a new clutch dog and cable might do the trick but not sure.

 

[cakopernik]

Re: 1980 Johnson 70hp Seahorse

Does anyone know of a good place to get cables and a clutch dog from on the net ?