1958 Johnson 7.5 Pressure to Fuel Pump Conversion.

[baconbiscut]

Hey guys, It's been a while since I last posted here but I'm having issue that I can't seem to figure out. I've got a 58 Johnson 7.5, that I would like to convert to a regular tank. I've followed the the instructions on the old omc site ( I'll see if I can find a link) but for some reason the doesn't create a enough pressure to pull from tank and feed it up to the motor. Does anybody have any ideas. Any help is greatly appreciated

-Dan

 

[Daviet]

Re: 1958 Johnson 7.5 Pressure to Fuel Pump Conversion.

The only thing that pulls the fuel up is the pump. Has it ever worked correctly? Are you running it in a barrel with the tank on the ground? Extra long hose with the tank in the bow of the boat? What pump did you use for the conversion?

 

[jbjennings]

Re: 1958 Johnson 7.5 Pressure to Fuel Pump Conversion.

Daviet has a good point----if the fuel tank is too low, even a correctly working fuel pump may not be able to suck it out that far. It sure had me baffled on my first conversion when my motor was in a 55 gallon drum and the tank was on the ground. I coudn't figure out why it wasn't working. Raised it up a little and Voila!
BTW, did you fully plug off one of the check valve ports and leave the other open?
JBJ

 

[baconbiscut]

Re: 1958 Johnson 7.5 Pressure to Fuel Pump Conversion.

http://www.outboard-boat-motor-repair.com/Johnson/Pressureized Fuel Tanks.htm

This is the website I used to do the conversion, I used the same parts, and the motor was on a
jon boat when I tested it so the fuel tank was probably not more than a foot below the carb. The motor runs fun as long as you keep the bulb hard, but as soon as you open it up with out squeezing the bulb it runs for a little bit then it just dies.

-Dan

 

[Daviet]

Re: 1958 Johnson 7.5 Pressure to Fuel Pump Conversion.

Has it ever operated properly?
Normally if you have to keep pumping the primer bulb it is a sign of a bad fuel pump. Have you tested the pump to see if it operating properly? Is the pulse hose producing a pulse?

 

[baconbiscut]

Re: 1958 Johnson 7.5 Pressure to Fuel Pump Conversion.

Yes, but it's very weak.

 

[Daviet]

Re: 1958 Johnson 7.5 Pressure to Fuel Pump Conversion.

Well, I guess if the pulse hose has a good pulse in it I would think your pump is the problem.