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thedeadsea

Older Johnson/Evinrudes w/double line hose conversion to single line

14 posts in this topic

I recently converted a mid 50's Johnson 18 hp from the old double line fuel system to a newer single line system. If anyone is looking at doing this, I would be happy to put up a little how-to article on it, just post up.

Steve

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That would be great.. there have been a couple of questions on that in the last 6 months.

If it's easier to e-mail, go ahead and send it to:

marine.man1@yahoo.com and I'll get it posted here.

marine_man

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Ok,

Here are the basics. If you want pics I can get some up next time I am at the cabin. If my descriptions aren't detailed enough don't hesitate to ask.

I did the conversion on a Johnson 18 HP, late 50's (not sure the year as this motor came to me for free as sort of a basket case and I haven't searched the model to determine the exact year)

First you need to find a donor motor that has the same powerhead as the motor you are converting (there are lots of blown or non functional motors if you look in the right places. Many HP motors use the same powerhead. 5 1/2 and 6 are the same, I think 7.5 and 10 are the same, and anything 12, 15, 18, and 20 Hp from mid 50's to the early 70's are identical.

I used our family's 57' 12 hp Gale Bucaneer (which seized a few years back) as the donor motor as Gale went to single line before Johnson Evinrude even though they were all made by OMC.

Step one: Remove the fuel pump from the donor motor. Remove the upper side plate from the donor motor (the one that has the single hose fuel pump mounted to it). When I say side plate, I mean the plate on the side of each cylinder on the right hand side of the powerhead. Remove the upper side plate from the 2 line motor. I actually had to drill out the side plate holes on my drill press as the Johnson used larger diameter bolts than the Gale. You will also have to use a low profile bolt on the bottom hole ( a regular hex head, not the actual slotted screw head bolts provided) when you reattach it to the motor as the thicker Johnson bolts will prevent the fuel pump from mounting properly to the side plate.

Inspect the side plate gasket. You will probably be able to salvage one of the gaskets. I paid the $1.75 and got a new one from a dealer (I referenced a 68’ 18 hp for the part #). Do not order directly from Evinrude/BRP as they charge something ridiculous like $7 to ship this very small part. Evinrude dealers order in bulk from BRP so they don’t charge shipping, although they may only order once a week or so depending on how large of a dealership. Also inspect the fuel pump to side plate gasket.

Step Two: Install the donor sideplate and then attach fuel pump to the side plate. Remove all of the double fuel lines and the male fuel line connection from the external part of the motor. Now it is time to run new lines (save yourself stress by replacing those 50 year lines right off the bat). Being the double lines are thinner in diameter than the newer single line, I had to run a clear plastic line through one of the double holes into the motor instead of the thicker rubber hose. Run the single line from the connector to the inlet of the fuel pump, and another from the outlet of the fuel pump to the carb. Be sure to clamp the lines, I use the rounded zip ties (which are OEM to newer motors and hold better than the old wire “clamps”.

Step Three: You no longer need the male connection that provided suction/pressure on the crankcase. Either remove the male fitting and replace with a blind plug, or what I did is attach a short piece of new plastic fuel line, squirt some high temp RTV into it, and then screw a small bolt into the hose before clamping it all together with a zip tie. MAKE SURE you let this cure at least 12 hours before turning over the motor to make sure no RTV gets sucked up into the motor.

Step Four: Remove the single line connector from the donor motor and bolt it onto the good motor. Attach to the fuel line with zip ties.

You are ready to fire up the motor. Remember these pre-60’ motors need a gas to oil mixture that is richer than 50:1. They recommended 25:1 using the old 50's era oil but I am experimenting with 32:1 on this motor to see if that will work with today’s better oil. I guess if I am wrong and it blows I have another old 15 horse that can become the next conversion.

The 18 always had problems running on the old double line system as it was always losing pressure from the old hoses. After the conversion it does 23 MPH on my 14' boat, slightly faster than my mid 90's 2 stroke Johnson 15 hp. Plus I love they way those old motors sound.

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I just did the single line conversion with a mikuni fuel pump on my 1956 johnson 15hp and it works great and was easy to do,

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Hey deadsea, is there anyway you could post some pics? I am not quite following the "donor" part - do you mean that the donor needs to be a single line fuel pump? Or just a second fuel pump?

Thanks!

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i could get you a pic of putting a pump on mine.. does it have some sort of pump already on it that you can take off? if yes chances are that a jhonson fuel pump for engines up to 50hp will fit on there..

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Thanks bl, would love to see the pic. I actually haven't even taken the cowl off yet. I wonder if I should even just not give this motor away... I guess it will be good for my grandson to learn some repsonsibility of maintaining it... smile I am giving it to him with a boat we fixed up together.

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HPIM0729.jpgfuel pump off a 45hp blown motor..

HPIM0731.jpgthese are the holes you need to look for..

this is a 5hp montgomery wards seaking but is the same as a jhonson..

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Thanks bl! that pooks pretty use to swap, once I find one. Any recommendation on where to find one? I know they are kinda speny if new.

Thanks!

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The Johnsons have an actual side plate that bolts onto the cylinder, the older ones don't have the suction hole so that is why you need a donor motor, I'll snap some photos, hopefully later this weekend.

Steve

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outboard junk yard, HSO-Classifieds, dealer or a junk jhonson motor.. but make sure you have holes or at least a hole like those first.. does the motor have copper fuel lines running to the carb? or is it hoses?

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Here is the new sideplate with fuel pump attached. (It is white because it came off a Gale Bucaneer).

utf-8BSU1HMDAyMjUuanBn.jpg

Here is the single line male fitting on the outside of the motor. I had to use nylon fuel line because the single line rubber hose was too thick to fit through the cowling.

utf-8BSU1HMDAyMjQuanBn.jpg

I plugged the suction vent line on the crankcase with a small piece of fuel line with a bolt and also RTV to ensure air wouldn't leak in.

utf-8BSU1HMDAyMjYuanBn.jpg

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Sorry for the poor clarity of the pics. Had to go directly from BlackBerry to Photobucket.

Steve

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