76 Johnson 70hp Outboard Motor

[jblushadow]

Hello! So me an my fiancé were recently given a free boat that needs some work to the engine. It turns over, but idles very high. We took it to a mechanic and they said it needed a lower crankcase seal because it sat so long. They quoted us about 1000 for it all, however it’s not really worth putting that much money in an engine that’s that old to us.

Now the question is, is it possible for us to try and repair it ourselves? If we couldn’t do it we were just going to sell it for parts and buy a new one. However, we would rather at least try and fix it ourselves. We are very familiar with dirtbike engines and work on them all the time, but boat engines are very different.

Any and all advice will be very much appreciated, thank you!

 

[racerone]

Actually those seals are very reliable.-----Does not matter if the motor sits for years.-----Sounds like you need to adjust some linkages to slow it down.----Post pictures of this motor.

 

[jblushadow]

I’m currently at the beach but i will post some when i get home. They said it was the lower crank seal because they sprayed carb cleaner on it and the rpms skyrocketed even more. That’s all they’ve done to it, didn’t even charge us anything. It is hard to change the linkages?

 

[racerone]

That is an impressive test to a novice !-----I would look for another mechanic who is trust worthy.----Should be easy to fix this high idle speed yourself.----Easy for me if I could see / feel and hear your motor !!

 

[jimmbo]

Perhaps it was a leaking Crank Case seal/Gasket, at least that, can be sprayed

Probably, as racer said, Misadjusted Throttle Linkage(s), happens a lot when Tinkerers start adjusting things, not knowing what they are, and then can't remember what they Adjusted or how much.

 

[jblushadow]

i figured it was worth us attempting to fix it, it couldn’t hurt much and i would love to just learn more about working on boat motors. I can try working on the throttle linkages to see if that helps any. Is there any special tools that you would need to replace the lower crank case seal?

 

[racerone]

I do not believe the lower crankshaft seal is the issue with this motor.----But a good mechanic can replace it in 2 hrs !!----No special tools required.

 

[jblushadow]

what else could be the cause of the jump in the rpms? I wasn’t there when he did it but I can try and do it again when i get home. I’m just hoping it’s something that we are capable of fixing

 

[racerone]

Forget testing with a spray of carburetor cleaner !-----You will see that carburetor cleaner will get sucked into the carburetors during this " testing procedure " by this mechanic.----Invest in a manual before you start adjusting anything on this motor.

 

[jblushadow]

thanks so much! i’ll try to find one

 

[jimmbo]

Don't bother with Hayden or Seloc Service Manuals, get the Model Specific(Factory) one