My 1957 Johnson Sea Horse 7.5hp AD-11 conversion

[Virgil2U]

I am planning on converting my old 1957 Johnson Sea Horse 7.5hp AD-11 outboard motor from the current pressurized tank system to the modern single line fuel system by using a pulse pump and installing a new single line fuel connector. I have made pictures of what I think will be a successful attempt but am not sure and I will gladly take any advice from anyone here for any changes they might think I should do.

 

[HighTrim]

Re: My 1957 Johnson Sea Horse 7.5hp AD-11 conversion

I personally do not like modifying the intake manifolds unless we are dealing with a CD. Lots of guys have had performance issues modifying the intake manifold on here, until we got them to tap the bypass for pulse. I would leave intake manifold alone. When done run a fuel line a few inches long from old pressure line and stick a proper sized bolt into it, effectively blocking it. It will be no longer needed. Take the bypass cover off before drilling/tapping, you dont want shavings in the powerhead.

 

[Virgil2U]

Re: My 1957 Johnson Sea Horse 7.5hp AD-11 conversion

I am not crazy about plugging up the intake manifold either, it was a procedure that was listed on the YouTube video and I was under the impression that this was the only way to do it to create the vacuum or pulse needed to operate the pump. I really don't understand by what you mean of using the old pressure line and plug it up. I had thought this line was necessary to run to the pulse pump for it to operate. If I am wrong or if you can show a picture of what you mean or which area to run the plugged hose it would be greatly appreciated. so far every site I have been sent to concerning this procedure it shows and instructs to plug the intake manifold with a vacuum cap.

 

[HighTrim]

Re: My 1957 Johnson Sea Horse 7.5hp AD-11 conversion

The bypass covers, which are behind the pump in your pic, need to be removed, drilled and tapped for a fuel barb. This is now where you get your pulse from. You leave the intake manifold alone. To complete the job, the OLD pressure line needs to be blocked off. Easy breezy. Modifying the intake manifold has to be done on the 5.5hp motors where the bypass covers are not removable. Here is one I just did, do not pay attention to the line routing though, they are mixed up on the pump, but gives you the idea.

 

[Virgil2U]

Re: My 1957 Johnson Sea Horse 7.5hp AD-11 conversion

OK I think I see what you mean. I am putting a picture of what I think you are saying. I want to thank you for being patient with me. I like so many off the disabled vets after being shot in the head do have some mental problems and do not think straight. I have been struggling with it since being shot in the head back in 93. But I do think I know what you are trying to show me better now since I have for some reason see it now as if for the first time.

 

[kbait]

Re: My 1957 Johnson Sea Horse 7.5hp AD-11 conversion

I call tim's outboard 218-682-2331 and ask for a bypass cover from a newer model that is already tapped for a fuel pump. If you don't have a fuel pump yet, they'll have a used one that will fit right on. And ask for the single line connector (it'll bolt to the twin line connector's spot). Get some 5/16" hose for connector to pump, and some 5/32" pump to carb. and use a small piece of the 5/32" to cap off the pressure outlet from the intake, as it's not needed now. Just capping it off works perfectly, done it many times. Good luck!

 

[Virgil2U]

Re: My 1957 Johnson Sea Horse 7.5hp AD-11 conversion

I called the number but it seems they are no longer in business. What do you mean by capping off the pressure outlet from the intake? Where is this intake located at? I had been under the impression that if I had tapped into that cover and run a hose from it to the pump that nothing needed to be blocked. I had thought I had finally gotten this figured out but now you have me completely confused.

 

[nwcove]

Re: My 1957 Johnson Sea Horse 7.5hp AD-11 conversion

kbait is referring to the pressure line that connects just behind the carb on the tiller side, and runs to the connector for the old style tank.

 

[Virgil2U]

Re: My 1957 Johnson Sea Horse 7.5hp AD-11 conversion

Ok I think I know what you are talking about. I have a picture to clarify that I would plug up the correct hose.View attachment 153948

 

[nwcove]

Re: My 1957 Johnson Sea Horse 7.5hp AD-11 conversion

yep, thats the one that needs to be plugged . as mentioned, just screw a small bolt into it.