1957 Johnson fuel conversion

[kazek]

Hi.i have 7.5 hp motor that I would like to convert to today's one hose fuel supply.i have read few posts already.what size of fitting should I use for bypass cover,is the size makes difference in the flow?.cover looks bit thin,so is there a special plate to be made to hold the nipple.i decided to go with Kawasaki fuel pump.Any help will be appreciated

 

[HighTrim]

Re: 1957 Johnson fuel conversion

The plate looks thin but holds the barb fine. Same sized barb as fuel line used, I personally use 3/16 ID"

 

[orbanp]

Re: 1957 Johnson fuel conversion

Hi kazek,

Here is an article about such a conversion:
http://www.leeroysramblings.com/Converting_dual_fuel_line.htm

Peter

 

[kazek]

Re: 1957 Johnson fuel conversion

hi.i like the plate conversion ,but dropped the idea after thinking that it may change combution pressure.any thoughts on that?thanks

 

[64osby]

Re: 1957 Johnson fuel conversion

Combustion pressure is in the cylinder. It will not be effected. The block pressure will be running your pump. Piston up less pressure, piston down more pressure.

I converted a 10hp Johnson using

the nipple on the manifold, the check valve was removed and one side plugged. So far it has worked great. I used the Mikuni pump.​

 

[HighTrim]

Re: 1957 Johnson fuel conversion

hi.i like the plate conversion ,but dropped the idea after thinking that it may change combution pressure.any thoughts on that?thanks

Nothing to worry about.

 

[kfa4303]

Re: 1957 Johnson fuel conversion

Here's a handy vid to go with the previously posted link. You can use several diferent brands of pump from OMC, to Mikuni to Briggs & Stratton, as well.

http://www.youtube.com/watch?v=FtG4M7ye1N8&feature=related

http://www.aircraftspruce.com/catalog/eppages/mikunifuelpump1.php

 

[kazek]

Re: 1957 Johnson fuel conversion

Thanks for replies,intell given was use full.i have done a hole in the bypass cover.looks neat.all a have to do now is use JB weld on it.i am off to make a mounting bracket and before I start drilling I want to know if there is relation on how long is pulse hose and went hole location

 

[HighTrim]

Re: 1957 Johnson fuel conversion

Ok Im confused, thought you were using an aftermarket pump?

 

[nwcove]

Re: 1957 Johnson fuel conversion

jmo, but jb weld isnt needed , and if any of it breaks off inside the bypass cover, your conversion will be for nothing, as it will destroy your powerhead. ( just did the conversion on a 7.5 with a b&s pump, four pulls on the cord for a motor that sat for years, and it runs every bit as good as a new one, half a pull after it ran....no jb weld required.)

 

[kazek]

Re: 1957 Johnson fuel conversion

I am talking about a little brass filter/exaust/went on Briggs pump(got that one because guy had it in stock).as to not putting JB weld...is there enough tread to hold the nipple in place?i dont want it to shoot out or anything like that

 

[HighTrim]

Re: 1957 Johnson fuel conversion

You do not need anything, there is enough to tap.

 

[kazek]

Re: 1957 Johnson fuel conversion

thanks guys.pump works.i end up using jb on the outside cause i could hear air suckinh in.used bigger (1/4 inch)fitting.anyway engine runs now,bit rough but its new treads topic.thanks again for guidenence