1955 Evinrude 15 HP fuel pump upgrade???

upnrunnin

Recruit
Joined
May 2, 2011
Messages
4
I have been doing a little online research on getting rid of the pressurized fuel can and upgrading to the single line by adding a fuel pump. I just picked up a 1955 Evinrude 15 HP model #15014 from Craigslist and would like to add a fuel pump to eliminate the pressure tank. The problem is that right now I don't have this motor in front of me. My parents picked it up for me and they are 150 miles south of me. Just looking for a "head start" so to speak. Does anyone have any information on what is involved in adding a fuel pump to this motor?? Pics would be great!

Thank you,
Jim Roberts
 

ONERCBOATER

Chief Petty Officer
Joined
Oct 11, 2010
Messages
536
Re: 1955 Evinrude 15 HP fuel pump upgrade???

not sure on this particular one, so i will answer in a very general fashion.
most 2 stroke outboard fuel pumps are powered by crank case pressure pulses. When the engine is running in a (two stroke engines case) the piston on the up stroke creates a vacuum (or low pressure) and draws fuel through the carb and reeds and into the crank case. On the down stroke the piston pressurizes the crank case closing (or allowing to close) the reeds, then the pressurized fuel air mix gets PUSHED into the cylinders.
This gives you one strong pulse per cylinder for every revolution of the engine. If you so choose to, or have the need to, you can drill and tap the case insert a threaded x barbed connector and use that line to power a diaphragm operated fuel pump. I haven't done this on an outboard before, but that said, I would not hesitate to do it if I had a fuel pump at hand and the need for one.
Things to consider 1st, where is the pulse that pressurizes the fuel tank currently coming from (my 1st guess is there is already a hole in case, and a reed (check valve) in place allowing you to pressurize the tank) can you use this hole to power your fuel pump?
If you must drill and tap your case, ideally you would take the engine down so that you could be absolutely assured that there would be no chips escaping from the drilling tapping operation. In reality this is generally considered to be too much trouble so the alternative is to drill very slowly using grease as a lube to catch the chips, if done with the right angle cut on the drill bit itself, the right pressure and speed you can get two clean ribbons of aluminum to follow the flutes of your drill and NOT get any in the case. Then comes time to tap it, at this point you do the same thing, use grease to trap the chips from the tapping operation, and remove and clean your tap regularly. I would feel amiss if i didn't point out that you should try this out and practice a wee bit 1st prior to attacking your dearly beloved (and expensive to replace) engine. This drilling operation is common practice in the Radio Control communities with both gas and nitro two strokes (though most times it is to provide a port to allow pressure for a smoke system on a RC plane though sometimes for remote or relocated fuel pump).
Remember to very carefully look at where you intend to drill, and what is BEHIND it before you drill. Make sure your drill bit is newly sharp and of correct size for the tap your going to use, make sure the tap is clean and don't break it off in the case. Also try to pic a location that won't interfere with ANY thing else. Oh and lost but not least by any means..... get the fitting 1st so that you know for a fact that you can get one you like before purchasing the tap and drilling the hole.

and make sure there is enough meat on the case (thickness) in the location your choose to get 3 or 4 threads cut in, less can work but 3 full threads is the minimum that I feel comfortable recommending

hope this was helpful in some small way.

Sean
 
Last edited:

HighTrim

Supreme Mariner
Joined
Jun 21, 2007
Messages
10,486
Re: 1955 Evinrude 15 HP fuel pump upgrade???

Go to the FAQs. There is a thread to help with the exact problem you are having by Tashasdaddy. It is complete with pics and easy to follow
 

upnrunnin

Recruit
Joined
May 2, 2011
Messages
4
Re: 1955 Evinrude 15 HP fuel pump upgrade???

Thanks for the tip. I am a small engine mechanic (former auto mechanic) and have no problem adding the pulse line (also a former machinist). I just wanted to know if there was a place already on this particular motor for a pump before I pick it up and look it over.
 

fish0holic72

Cadet
Joined
Mar 28, 2011
Messages
13
Re: 1955 Evinrude 15 HP fuel pump upgrade???

I just converted my '58 10hp sportwin last week. I acquired a by-pass plate from a '60 and newer evinrude that was already ported for a fuel pump. I drilled and tapped it out to 1/8th in pipe thread and bought a brass barb fitting to install. I mounted a fuel pump elsewhere on the motor and ran my hoses to it. Don't forget you will have to take a short piece of hose and plug your intake fitting. I just bought a walbro fuel pump that is used on john deere lawn mowers. It runs like a champ. would be glad to help you out if you have any more questions.
 
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