Vintage Johnson dual line gas tank - fit Evinrude 5.5?

[daveh77]

Greetings,
This tank came in the 1957 12' skiff we bought. It appears to have the same connector as the 1959 Evinrude 5.5 that I got from the shed, indicating that perhaps this motor was on this boat.
I was looking at the motor for a fuel pump but after looking at the tank, I guess the motor pushes air to pressurize the tank to push the fuel. Is that how it works?
Amazingly, the inside is clean and rust free.
Suggestions for testing, resurrection, alternatives, etc?
Thanks, Dave

 

[F_R]

Correct, it is a pressure tank and will work on any Johnson or Evinrude motor with similar connectors. There are three different versions of the tank top, if you decide to rebuild yours. You can eliminate the first type because you have the plastic push button. You would have to take it apart to tell if it is type two or three.

 

[daveh77]

So how functional are these vintage pressure tanks? What typically fails on them? How hard to get parts to rebuild them?
Or just update to a different newer/better system?
Pro & con of keeping this system vs 'updating'?

I am also needing to supply fuel to a Ted Williams 7.5 without a built in tank, and an early (1976-80?) Tohatsu M9.8A. I don't know what type of tank or fuel system those had.
I also have a late 1960s Mercury 60 - 6hp that has a generic hose and bulb (old & sunbaked) clamped on it. Probably the least likely to run any time soon.

For simplicity and interchangeability, it would be convenient to have the same fuel tank set up for all 4 motors.
However I am not opposed to keeping this pressure tank with the 5.5 Evinrude because they are the original set up, as long as it is really functional and reasonably trouble free.
I have restored enough vintage cars and equipment to place value on keeping vintage things original but I place bigger value on actual function when out on the water.

I assume many of you have more than one brand of OB. What do you do for the simplest functional fuel tank set up to serve several different motors?

At this point, I don't know which of these motors is going to be the first to get running. Need quick, simple, and affordable for testing. I can gravity feed from above for basic testing but need advice on fittings for doing it that way. Can I gravity feed that Evinrude while trying to get it to run before messing with the tank?

I also have a couple of newer plastic tanks with just one larger hose fitting.

The other factor is fuel/oil mix ratio. I have read many different opinions on the required mix for these various vintage engines, from 16-1 up to 50-1.
I know from my MX days in the '70s and my logging chainsaws in the '80s, that "required" mix ratio is very much dependent on the quality of the TSO.

Now that I think this through, the air cooled Clinton engine needs different TSO than the others that are water cooled, correct?
For it I would be inclined to use Stihl chainsaw oil at 40-1 or even 50-1?

Are there hard design issues that would require the 1959 Evinrude, the 1976 Tohatsu, and the 1968 Merc, to each require different oil or ratios? Bushings vs bearings, etc?
Guessing the Tohatsu & Merc can run leaner mix but maybe old Evi needs a bit richer even with better modern oils?

Now thinking a one size fits all fuel set up is not possible or practical after all.
Maybe the pressure tank and richer mix for the Ev 5.5, a tank for the Sears with air cooled TSO, and a 3rd tank of water-cooled TSO for the Tohatsu and Merc?

Maybe its a good thing that I have the pressure tank and 2 newer plastic tanks.
As you can tell, new to all this and trying to figure it out.

Thanks,
Dave

 

[lindy46]

Tanks are pretty trouble free. Gaskets and o-rings can fail with age and there are rebuild kits if needed. Try it out and see if there are any leaks anywhere and see if it holds pressure. After running the motor for a short time the pressure should build. Just unscrew the tank lid and you'll hear the air pssssst out if it's holding pressure. If yours is clean inside it may be good to go.

 

[Kawaiikeno]

I have 2 of the 50's Evinrudes that take the pressure tanks and like you I thought about converting them to single line and actually did on the 1958 7.5hp.
But after almost running it on a 50/1 mix I unhooked the pump and went back to pressure tanks this way I know if its a pressure tank it's 16/1 mix, another habit I have is to always add the oil in the tank before the gas this way I know if there is gas in a tank there is oil also.
Mike

 

[Crosbyman]

my only issue I had with a 7.5hp & pressure tank is that a pin hole (rust) caused 5 gal to leak and fortunately got dump out the boat which was tilted back with the plug removed. the lawn suffered major..total destruction.

I switched it to a pump and modern tank....my 75hp ETEC uses an onboard tank so no mix-up possible.... I since moved up a few years to 9.5hp


theB&S pump was mounted on the back bracket . & .worked great

 

[daveh77]

Thank you all for your input, very helpful and appreciated.
I'm starting to get some of this outboard stuff figured out, thanks mostly to this forum and the experienced people who contribute here.

The engine pressure pulses off the crankcase feeds pressure through the air line (actually fuel vapor/oil mix in a 2 stroke) to the sealed tank, hence pushing the fuel uphill to the carburetor.
Sounds like it should work pretty well after its running.
So without a pump or primer bulb, how does the fuel line and carb bowl get filled and primed before a running engine creates the pressure?

 

[cc67]

There is a pump on the tank. You have to manually pump fuel to the carburetor.