1959 Johnson CD-16 performance issues

[Sea Donkey]

I just finished rebuilding the lower unit, rebuilding the carb, and replacing the points and condensers. I adjusted the carb with the motor warmed up and sitting in a garbage can full of water. I adjusted the car and the motor screams! It really runs smoothly. Tonight I took the boat out on the water and was disappointed by the performance. The engine runs great but when it's in gear and I got to WOT it just doesn't wind up. It runs smooth but doesn't wind up like it does when it's in neutral. The engine did wind up in gear prior to this rebuild, so I'm stumped. I played around with the high speed mixture screw, but no luck...
Any ideas?
Thanks!

 

[Mas]

Re: 1959 Johnson CD-16 performance issues

Welcome!

What's the compression numbers on the motor..have you checked?
Put a mark across the prop hub to see if it is spun. If the marks move in relation to each other, the prop hub is spun and needs to be fixed.

Also, it's not a good idea to rev up the motor in neutral.

Mas

 

[1946Zephyr]

Re: 1959 Johnson CD-16 performance issues

This motor could have an issue with the shock absorber. If the spring inside breaks, then you'll have all kinds of problems.

 

[Sea Donkey]

Re: 1959 Johnson CD-16 performance issues

Welcome!

What's the compression numbers on the motor..have you checked?
Put a mark across the prop hub to see if it is spun. If the marks move in relation to each other, the prop hub is spun and needs to be fixed.

Also, it's not a good idea to rev up the motor in neutral.

Mas

Thanks for your response! I have not checked compression. The motor ran fine prior to installing new seals in the lower unit and installing a new water pump. I figured as long as I did that, I would freshen up the carburetor too. I doubted the problem had anything to do with the prop hub spinning, but I checked it anyways...all is good. Thanks for the warning, but I am aware of being careful to not over-rev the motor with no load. It just seems odd it revs up fine in neutral but not in gear. When I put the motor in neutral the prop spins freely, so I know it's not a tight bearing or anything like that. Also, when I pull on the starter rope while it's in gear, it doesn't seem to have excessive resistance either. I'm beginning to think it's a ignition problem. I used my ohm meter to set timing, but I'm going to take another look. This is just too weird...

 

[Sea Donkey]

Re: 1959 Johnson CD-16 performance issues

This motor could have an issue with the shock absorber. If the spring inside breaks, then you'll have all kinds of problems.

Shock absorber? Are you referring to the spring right under the power head where the drive shaft goes in? That was fine when I put it together. How would that affect my problem? Thanks for your response!

 

[F_R]

Re: 1959 Johnson CD-16 performance issues

The shock absorber is that short shaft inside the lower unit gearcase. You saw it when you re-sealed it. If it breaks, it grows in length and binds up under load. That may or may not be your problem.

Most likely, your motor is running on one cylinder. They will run fine on one, just no power. Check your ignition, sepecially the coils.

 

[steelespike]

Re: 1959 Johnson CD-16 performance issues

2nd the motion,check that it runs on both cylinders.

 

[Sea Donkey]

Re: 1959 Johnson CD-16 performance issues

I've been meaning to post for awhile....I found my problem. I messed around with it on the lake and thought, I'm going to try unplugging a spark plug one at a time. Sure enough, I had a bad plug/wire connection. It was kind of funny to come back to the forum and see two suggestions to look in that area! My motor now runs like new! Good for another 52 years

 

[Sea Donkey]

Re: 1959 Johnson CD-16 performance issues

The shock absorber is that short shaft inside the lower unit gearcase. You saw it when you re-sealed it. If it breaks, it grows in length and binds up under load. That may or may not be your problem.

Most likely, your motor is running on one cylinder. They will run fine on one, just no power. Check your ignition, sepecially the coils.

Thank you for attaching that thumbnail. My motor does not have that part. I could definately see how that could cause a problem though!