140 Johnson "Snatching"

[leftofcentre2006]

I have a problem with my 1980's motor.

It seems to have developed a problem where the engine stops for literally a split second at a time during cruising/full throttle.

I think its an electrical fault as i have had misfires/fuel starvation before and the results arent so pronounced or violent.

At first i thought it was a Trim fault and the boat was "digging-in" whilst on the plane. However i have established that this is now not the case.

Any ideas on where to start looking?

The sensation feels like the boat has run-over something or like i said above, almost like its "digging-in". The engine never dies or stops completely and this happens i would say once every 2-3sminutes.

Cant be doing the engine much good!

 

[F_R]

Re: 140 Johnson

Re: 140 Johnson

What you are describing sounds like a problem that is very common on older/smaller motors. What I'm thinking about is it is jumping out of gear and immediatly back into gear. Feels like you ran over something allright. It is caused by worn out clutch dog and forward gear on those motors.

 

[imported_lorin]

Re: 140 Johnson

Re: 140 Johnson

It does sound electrical so there could be many causes so you want to check the things that are easy to check first. Two things that are easy to check are the kill switch and the ignition switch. Find the black wire that goes from the powerpack (one powerpack?) to the kill and ignition switch. Find where it goes into a plug and disconnect the plug. Then run the motor and if the problem is gone then the problem was the kill or ignition switch. You'll have to choke the motor to turn it off now.

 

[emdsapmgr]

Re: 140 Johnson

Re: 140 Johnson

Could be a worn clutch dog, slipping. Check your shifting linkage/cable to be sure it is fully engaging in forward.

 

[tashasdaddy]

Re: 140 Johnson

Re: 140 Johnson

remove shift cable at the engine, and shift manually, try taking it up to speed, and see if it does it. if this solves the problem, you have an adjustment problem with the shift cable, or a streached shift cable, and needs replacing.

 

[leftofcentre2006]

Re: 140 Johnson

Re: 140 Johnson

Hmmn food for thought on the jumping into and out of gear.

I can only imagine what state the gear teath must be in. Some forces at work there at full throttle!

Can the gear cable be adjusted without buggering up the throttle handle?

Thanks for the help folks (from many miles away i see)

 

[emdsapmgr]

Re: 140 Johnson

Re: 140 Johnson

The shift adjustment is back by the engine under the cowling.

 

[leftofcentre2006]

Re: 140 Johnson

Re: 140 Johnson

Hmmn

A fellow British boat forum reckons i am going in the wrong direction with gearbox slipping/jumping and that the problem is more likely to be electrical.

Perhaps Capacitor?

Conflicting opinions indeed.