6hp Johnson Seahorse

[BLJC27]

Hello,
I have a longshaft 6hp Seahorse on a 14 v-bottom jon boat. I know that this boat needs a shortshaft motor, but I don't have the funds at this time.
Here's the problem. This motor starts and runs great, but when it is on the boat, it is very, very slow. In fact, it runs about as fast as a 2hp evinrude shortshaft that I have.

Here's my question. If I build a transom extender to raise the motor, would it make a big difference? I know that it won't make a huge difference, but will I be able to tell the difference? Or is there a problem with the motor? Like I said, It runs great, but I may be missing something. I plan to get a bigger shortshaft later, but it's just not an option right now. I would appreciate any help.

Thank you
Barry

 

[PW2]

Re: 6hp Johnson Seahorse

You didn't give much info, so anything posted would simply be a guess, but that motor should perform better than you describe.

My guess is you are only getting power out of one cylinder. Whether that is a carb issue, or perhaps a spark (or compression) issue is impossible to determine without some further info.

 

[tashasdaddy]

Re: 6hp Johnson Seahorse

running properly with a transom elevator you will see the difference. i would check spark and compression on both cylinders, i would also pull plug wires one at a time, then replace, the motors should run with one wire pulled, but the rpms will drop. if it runs on one cylinder, and not the other, you need to find out why one is failing.

this is a 50 hp on a transom elevator.

 

[BLJC27]

Re: 6hp Johnson Seahorse

Thanks for the quick responses. I'll check that this evening and let you know what I find. If it is running on only one cylinder, what are some of the common reasons and fixes for this problem? Would it be something simple to fix or would it likely be a big problem? I know you can't tell me specifics without knowing the exact problem, just trying to get some ideas. (I'm new to the world of outboards)

Thanks again
Barry

 

[BLJC27]

Re: 6hp Johnson Seahorse

UPDATE
I went home on my lunch and checked the motor. Here is what I found.

85 - 90 lbs compression in both cylinders (is this good)
and
good fire on both cylinders
I remember that the guy that I got this from said that he had the carb rebuilt last year. The plugs also look good.
Is there anything else that I could check? Or do you guys think that it could be from the drag of a longshaft on a shortshaft transom?

I looked for the Model and Serial #'s but the plate is missing from the transom bracket and I couldn't find the silver plug on the side of the motor like my 2hp Evinrude has. I believe that this is a late 1960's or early 1970's Johnson seahorse.

Thank you for the help
Barry

 

[PW2]

Re: 6hp Johnson Seahorse

That compression should be fine.

If the spark is fine, chances are it is a fuel problem. maybe a high speed jet clogged?

Can you tell what the RPM's are?

You'll certainly get better performance with a proper transom height, but I don't think you'll get twice the performance. I've got a six on a relatively heavy 17' boat as a kicker, and I get 6-7 knots full throttle at about 5000 RPM.

 

[BLJC27]

Re: 6hp Johnson Seahorse

I'll try to check the RPM's tonight and get back with you.
Thanks again for all the help.