# Need help regarding older OBs that use Pressurized Gas tanks



## BloodStone (Mar 8, 2009)

*Hey gang;
Anybody know how to do a conversion on a 1957 Evinrude outboard from a 2 line pressurized fuel tank to a one line standard gas tank? Because these metal monstrosities are holding up my boat mods (big & bulky). Also, would one 6 gallon fuel tank suffice with an 18 hp or do I really need 2?
Thanks*


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## Mike Redmond (Mar 8, 2009)

:idea: Hi,there's a book called Cheap Outboards BY Max e .WawrzyniakIII..you can order it through Amazon....or you can go to a site called Duckworks Magazine on the internet,once there you can look in their archives,there is an article that pretty much describes what to do and how to work on your vintage outboard...as long as it is a Johnson/evinrude hope this helps. Mike Redmond


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## bassboy1 (Mar 8, 2009)

Mike Redmond said:


> :idea: Hi,there's a book called Cheap Outboards BY Max e .WawrzyniakIII..you can order it through Amazon....or you can go to a site called Duckworks Magazine on the internet,once there you can look in their archives,there is an article that pretty much describes what to do and how to work on your vintage outboard...as long as it is a Johnson/evinrude hope this helps. Mike Redmond


Or, do like I did, and get the book from the library, and save 20 bucks. Good book, worth the read, if you have any interest in smaller outboards. 

Here is a link to where somebody did it. I know him fairly well, so I can email him if you have any further questions.
https://forums.iboats.com/showthread.php?t=205628


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## CarlF (Mar 8, 2009)

Also, would one 6 gallon fuel tank suffice with an 18 hp or do I really need 2?

I have an 18 hp on my boat. I've taken it 10-15 miles up river and back, maybe further, and I've never come close to running out of fuel. Used a 1/2 tank maybe. So unless you are planning on making long range runs, I cant imagine needing 2 - 6 gallon tanks on board. 

That said, if you are really worried about it, get out with a full tank, run a set course of known mileage/time and then re-fill and check your mileage/gallons per hour.


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## Macgyver (Mar 8, 2009)

I did it on a 57 5.5 HP . it is the same difference . hollar at me if you need details...


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## duke (Mar 8, 2009)

on a long trip take a couple of gals i a gas can along if you think you need them.it should help gettig back or to a marina that has gas.


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## BloodStone (Mar 9, 2009)

> Or, do like I did, and get the book from the library, and save 20 bucks. Good book, worth the read, if you have any interest in smaller outboards.
> 
> Here is a link to where somebody did it. I know him fairly well, so I can email him if you have any further questions.
> https://forums.iboats.com/showthread.php?t=205628



*Thanks Bassboy but iboats wouldn't let me see the pics (gotta be a member). Is it possible you can PM me the pics or the entire article? Also, this may sound really ignorant, why can't I just use an inline electronic fuel pump as long as I take proper precautions regarding gas fumes?* :-k


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## Macgyver (Mar 9, 2009)

the pressurized fuel tanks used one way valves in the intake to use crankcase pressure to put pressure in the tank. all you need is to remove those one way valves, block off one of the holes so it doesn't cancel out the "pulse" from the other hole. route the line to a pulse fuel pump.

this is done because natural crank case pressure works on a push/pull basis. the old jonnyrudes used the one way valves to only get the push of the pressure. you can't just take out the valves and be done with it as one is pushing while the other is pulling so they'd just cancel each other out if you didn't block off one of the ports.

I made a new gasket and just didn't cut out a hole for that port and also stuffed a portion of a vacuum hose cap in the port. these can be bought cheap at any auto parts stores. 

I did have a web paged saved that detailed all of this but it seems to of changed..


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## BloodStone (Mar 12, 2009)

Found the following response on iboats in regards to my question that someone had asked previously. Is he correct or is it overly simplistic :BS: Thanks
Btw, sorry for no pics both the wife's & daughter's digital cameras took a dump so.. #-o 



> The easy way is to get a fuel by-pass cover from a newer 18, 20, or 25 HP motor. This is what the pump screws to. Use the same pump as any of these engines'. The cover will bolt right in. The single line fuel connector will also bolt right in.


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## Macgyver (Mar 12, 2009)

that won't work on a 57'


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## Ouachita (Mar 12, 2009)

Macgyver said:


> that won't work on a 57'


I did this on a 58' Johnson 18hp. The bypass cover from a 66' Johnson 20hp I had fit exactly. I just put the bypass cover and the fuel pump from the 66' right on it. Was the 57' made differently?


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## Macgyver (Mar 12, 2009)

my experience is with a 5.5 hp . I stand corrected...if it works on a 58' , then it should work on a 57' as they shouldn't be any different ..


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## flintcreek (Apr 18, 2009)

Blood Stone, did you get it converted to single line tank? If you can not find a by pass plate from a newer model you can drill a hole in your old by pass plate and JB Weld in a copper tube in place and use a lawnmower vacuumn type fuel pump. Connect it up with a vacuum hose, mount it somewhere under the cowl hook up the fuel lines. It is not hard to do at all....Did a old 56 model 10 hp Johnson about 8 years ago.

G.M.


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## CGH (Apr 29, 2009)

BloodStone, if you can't find that book, i have a copy of it that was sent to me!

Any helped need just give me a hollow.

BTW I have the same motor and will be changing mine to single line too!


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## walkeraw (May 5, 2009)

The conversion, as others have mentioned, is very easy to do. A few years ago, I converted my 1955 Evinrude 15hp by following the article on Duckworks magazine --> https://www.duckworksmagazine.com/05/columns/max/5/index.cfm

Very easy to follow, has photos, etc. I already had some RTV/silicon/whatever onhand, so my only cost was ~$24 for the purchase of a Mikuni pulsed fuel pump (like those used on chainsaws/snowmobiles/etc.). Works great!


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