1975 Johnson 25 won't run above idle in gear under a load.

[80stumpknocker75johnson25]

Got this older motor from my uncle been bringing it back to life so far I've done a carb rebuild,fuel pump and lines(except line from fuel tank),points kit,impeller and plugs (I have not replaced coil packs).
I have great spark on both plugs and it runs fine in the bucket at the house in all gears and ran good for 2hours after everything was done planed out ran 22mph no problem.when I get out in the lake now forward gear won't go above a high idle reverse throttles up fine it idles great shifts good I replaced the drive pin after the last ride it was a little old but not to bad but now I got no clue as to why it won't run in drive like it used to.

 

[racerone]

Maybe the propeller is slipping ??

 

[Crosbyman]

could be just carb dirt again from that tank hose you did not change or dirty pick-up check venting ..recheck compression etc.. and sparks more to come surely.. check fwd linkage

 

[80stumpknocker75johnson25]

Maybe the propeller is slipping ??

I thought so too after reading a few forums but the rpms don't go up. I pulled the prop anyway looked around and replaced the drive pin while I was there.

 

[Crosbyman]

Maybe the propeller is slipping ??

wouldn't RPMs peak with prop slip... seems OP can't get it to get high rpms in fwd

 

[Crosbyman]

I thought so too after reading a few forums but the rpms don't go up. I pulled the prop anyway looked around and replaced the drive pin while I was there.

if rubber hubbed....rubber could still slip with a new drive pin... mark the prop and rubber insert with a scripto ... do a run and recheck if marks are aligned or not ...!!

 

[80stumpknocker75johnson25]

rubber could still slip with a new drive pin... mark the prop and rubber insert with a scripto ... do a run and recheck if marks are aligned or not ...!!

Will do I'll get a compression test this weekend and get a new outside fuel line and I'll post back

 

[racerone]

????-----" forward gear won't go above high idle "----That statement could mean different things to different people.----Could be many things to check.-----Motor might be running on 1 cylinder for any number of reasons.------I should refrain from giving simple advice on this one.-----Stepping aside for now.

 

[80stumpknocker75johnson25]

wouldn't RPMs peak with prop slip... seems OP can't get it to get high rpms in fwd

I can get high rpms in forward at the house in a trashcan no problem it when I put it out on the lake and try to push the boat it's like it hits rev limiter in forward no pops or skips or anything just won't go anything above a high idle speed

 

[racerone]

Some simple inspections to do on your part.

 

[80stumpknocker75johnson25]

Some simple inspections to do on your part.

Any idea on where to start?

 

[saltchuckmatt]

Carburetor.....but what test did you do to get "great spark"

 

[80stumpknocker75johnson25]

Carburetor.....but what test did you do to get "great spark"

Ill pull the carb again and I pulled the plugs and started the motor.good blue spark on both cylinders

 

[saltchuckmatt]

Ill pull the carb again and I pulled the plugs and started the motor.good blue spark on both cylinders

3/8 jump on a spark JUMP tester?

 

[James6]

Will the throttle go to the fast setting? If not linkage needs adjusting