1975 Johnson 15hp Carb Settings

[nearbottom]

I just bought a new (to me) 1975 15hp Johnson. The previous guy claimed to be a mechanic and did all kinds of work rebuilding it. I am finding out now he was not such a good mechanic. I have gone through the motor and corrected some of his work but I am wondering if anyone can tell me what the carb settings should be for this motor?

 

[bktheking]

Re: 1975 Johnson 15hp Carb Settings

There is only one setting and then adjustment, seat the slow speed adjustment needle and back it out a turn and a half and adjust it from there, in the lake of course.

 

[Daviet]

Re: 1975 Johnson 15hp Carb Settings

The only setting on your carb is the low speed, set 1 1/4 turns out from lightly seated and fine tune with the boat in the water.

 

[jmendoza]

Re: 1975 Johnson 15hp Carb Settings

Check to see if the throttle cam is synched with the throttle, the cam is on the magneto plate. Rotate the throttle grip to slow, then slowly open the throttle and note when the cam begins to open the carb butterfly. The carb has a linkage with a plastic roller that rides on the cam. There is a mark/arrow on the cam, when it lines up with the roller, it should be just at the point where it starts to open the throttle. You can loosen the two screws holding the cam to the magneto plate to adjust it if needed.

A 12 volt battery and timimg light can be used to check the timing without removing the flywheel, this is a points type ignition(the most reliable too), but you really need the service manual for the specs and pictorals of how to adjust the points if the timing is off.

It is not uncommon for engines this old (I have a 1975 too) to require new upper engine mounts, and a new upper water tube grommet. I just had to replace my lower unit/gear case seals last year as well.