converting older dual fuel lines to a single fuel line

[bplayer405]

I have a '57 Johnson 18 HP Seahorse outboard that I was going to sell before doing a little research. I wanted to have a motor to use as a backup for my 48 HP Mariner to fish HP restricted areas. I just didn't want to run two seperate fuel systems from to front of my 16' decked Jon to the back. The Mariner is a single line system. My research showed an epoxy or rubber plug to stop the pulse flow in one side of the two ports in the reed plate where the check valves supply pressure for the two line tank. So I started taking apart my outboard. I removed the carburetor and linkage, removed the intake manifold, and removed the reed plate. On the reed plate I removed the check valve assembly below the reeds, required to have a pulse signal to a fuel pump, and checked the passage ways through this area. Brainstorm! Plate is aluminum. Epoxy or a rubber plug in this area could fail from fuel coming in contact. Why not use aluminum? I found a aluminum bolt left over from my transom overhaul and it fit the port in the reed plate perfectly. I cut it off short enough to use a hammer and swell the port shut like using a rivet. Then I filed the excess below gasket thickness. Now the port is sealed leaving one port open for a pulse signal for an aftermarket fuel pump using the existing fitting on the manifold and it cost only my time to tear the intake down. I feel using an aluminum bolt or rivet is a more solid and permanent solution to this modification and it still can easily be reversed if the need arises.

 

[kbait]

Re: converting older dual fuel lines to a single fuel line

Curious.. are you going to run your mariner at 24/1 or your Johnson at 50/1 from your single fuel system?

Welcome to iboats!

 

[RogersJetboat454]

Re: converting older dual fuel lines to a single fuel line

Welcome to Iboats.

Truthfully, most of the fellers around here don't mess with the intake, and instead tap one of the bypass port covers on the block for installing a nipple to supply the pulse to the fuel pump. Much easier, and completely reversible with out having to pull the engine apart...

 

[HighTrim]

Re: converting older dual fuel lines to a single fuel line

I find, as stated, that modifying the intake manifold on the Big Twins can cause running issues. Much better to get your pulse from the bypass cover and plug the old pressure line.

 

[kfa4303]

Re: converting older dual fuel lines to a single fuel line

HI bplayer. Welcome to iboats. Here are some great links that can walk you through the entire conversion process as well as a few general maintenance links.

Converting the Old OMC Dual Fuel
HOW TO CONVERT 50s motors from two line tanks - YouTube
Maintaining Johnson E & FD Serie
1957 Johnson FDE-11 18 hp Outboard Motor Parts

 

[F_R]

Re: converting older dual fuel lines to a single fuel line

bplayer, it sounds like you have already determined to go into the reed plate for your conversion. That's ok with me if it is ok with you. Personally, I'd have just bolted on a later model bypass cover and OMC fuel pump and be done with it. But that's just me.

For the record, your 18hp is all needle / roller bearings, basically same as the the newer 50:1 models. Y'all guys can fight it out over the fuel mix question.

 

[nwcove]

Re: converting older dual fuel lines to a single fuel line

i agree with the above in regards to the conversion.....you definitely took the hard route! that style conversion is done on the 5.5's as there is no other option.
as far as the 50:1 vs 24:1 on the 1957 motor......id paddle before i ran 50:1 through it. and if you do decide to go with 50:1, i would paddle now and then just to get used to it !! jmo

 

[bplayer405]

Re: converting older dual fuel lines to a single fuel line

Thanks for the input. I actually have two 6 gallon plastic tanks in my boat. My original thought to use both for weekend trips or long runs with either motor. I could run one for each outboard though. 50:1 for the Mariner and 24:1 for the '57 Johnson.
Maybe I went the harder route on doing the conversion. It was actually a pretty simple mod. The nice thing about it is that I can swap motors and use the same fuel line for either!

 

[bplayer405]

Re: converting older dual fuel lines to a single fuel line

To kfa4303: all good links and I've used all but the one showing the mounted fuel pump on the bypass cover. Makes perfect sense... I could've drilled and tapped a fitting right in there. Or find a cover with the mod.

 

[bplayer405]

Re: converting older dual fuel lines to a single fuel line

One more thought on this. I like the fact that the check valve on the the reed plate is removed on the mod I performed. There's no pressure built up and captured in that area of the intake possibly causing a leak later. Should have the pump and fitting to finish my mod this coming week. I'll post back to anyone curious about it possibly not running right.