TROUBLE SHOOTING 25H.P. JOHNSON

[tuna]

i have a 1980 25 h.p. johnson that i am having a issue with. the engine does not seem to speed up as much as it should. i have adjusted the carb and it did not make much of a differance. i have been told that it could be a carb kit or head gasket. does anybody have any other ideas ? gotta get ready for open water asap.

[JoeFisherman]

Is it possible it's not firing on all cylinders?

[tuna]

it has new coils, fuel pump, and i see the guy i bought it from last year put 1 new gasket on the head but did not replace the inner one. there is 2 gaskets on the head

[Randy Kaar]

check the compression, if a head gasket is leaking you will
have lower compression on that cylinder. Very possible the
carb is dirty.

randy

[HUNTER2]

I had a older engine that was a 20hp. There was a valve that looks like a flower with peddels inside the engine. One of the peddels broke off and it was like it was running on 1 cylinder. Then about a year latter the other one did the same thing. I'm not sure what that valve is called, I think it is a reed valve.

[Jdrummer]

It could be a plugged pick up jet. carbs usually have two jets. one idle and the other the pick up. the pick up jet is used and effects the throttle response and sometimes (if plugged) it will not run as fast as it should . Did you winterize it properly last fall?

[JCAMERON]

Like randy said, make sure you have compression. A carb kit couldn't hurt. Also be sure your cabs are synchronized.

[tuna]

havent got a chance to check the compression yet. just went and bought a new tester. i did winterize it though. once this weather gets better i plan on checking it out.

[JoeFisherman]

A little water in the gas?  Air leak in the gas line?

[groma]

I had trouble shooting a 25hp Johnson one time....... So what I did is waited til dark and snuck up on it from behind    put a round right between the cylinders !   Sorry I couldn't help it.

[Jdrummer]

I had trouble shooting a 25hp Johnson one time....... So what I did is waited til dark and snuck up on it from behind    put a round right between the cylinders !   Sorry I couldn't help it.

come on now

[finch]

I had trouble shooting a 25hp Johnson one time....... So what I did is waited til dark and snuck up on it from behind    put a round right between the cylinders !   Sorry I couldn't help it.

come on now

I was wondering how long it'd take for a joke like that in this thread...

[Bufflehead]

Seems trouble with a Johnson is going around



 

[finch]

on a more productive note...

have you checked compression yet?  that would eliminate that possibility of a problem.

I would say to check your throttle linkage and make sure there are no binds.  also check your choke lever, the one on my 4 horse johnson broke off inside the cover so when I was moving the lever in and out I actually wasn't even moving the choke butterfly in the carb.

if those two are good, pull a bowl off one of the carbs and see if there is a yellow film on the inside, if there is, buy 2 rebuild kits and tear 'em both down.  be sure you get them synchronized or you will have even bigger carb related problems down the road.

[tuna]

checked the compression and found out it was only 80 psi in the upper cylinder and 100 psi in the bottom one. i put the new gasket in and they went up to 120 psi in both cylinders. seem to be running great and smoooooooth . i brought it out last night for opener and it is running alot better but still does not seem to go as fast as it should. it does go faster than last year . reved up great at home but when i got it out on the lake it seemed to be a little slower when you  get the weight behind the motor.