Johnson- Super sea horse has high speed miss?

[Specs11]

I just joined and am looking for some help. I have an old Johnson-super seahorse out board, I'd imagine its around 30-40 horse but am not positive. When I take the boat out the engine runs and then when I put the boat in gear it cruises. When I go decently fast the whole engine kind of pops and bounces the transom. Is this pre ignition or something like that? I thought it may have been the hub on the prop so I replaced it as well as the plastic coupling and cotter pin and the pin that holds the prop on the shaft. I would like some help or suggestion?!

Thanks,
Specs

 

[kfa4303]

Re: Johnson- Super sea horse has high speed miss?

Hi Specs. Welcome to iboats. cool old "Big Twin" motor you' got there. It sounds like it coudld be one of two things wither an issue in the gear case and/or a lean mix in the carb. If it feels like you're hitting a log/submerged object, then your clutch dog is probably worn causing the motor to slip out of gear at high speed. It's a somewhat common problem after 50 years of use. To replace the clutch you have to open the gear case and install a new one. However, before you do that, you may want to check that the shift shaft rods are prorperly connected. If it's not an issue with the lower unit then you're probably having a bit on a lean sneeze/pop at high speeds due to a lack of fuel in the mix. With any luck you can simply back out the hi speed needle on the carb (the lower one) about 1/8-1/4 of a turn. Of course, it's probably best to clean/rebuild the carb if it hasn't been done in a while. Not to worry, it's a DIY job and you can get a kit right here at iboats for about $25. Either way both jobs are DIY and parts are still readily available for each. Here's a handy link to familiarize yourself with the motor. If you look on the transom clamp you should find a small metal tag riveted in place with the model and serial number on it. That will help us nail down the exact year.

Reviving a Vintage Big Twin - Part 1

 

[boobie]

Re: Johnson- Super sea horse has high speed miss?

Model # ???

 

[Specs11]

Re: Johnson- Super sea horse has high speed miss?

Thanks for the help so far guys I really appreciate it!! I will get the serial/model number after school today and post it in this thread! Hopefully you guys can help me out some more!

Thank you!!