Please explain the fuel supply system on these old metal cased Johnyrudes

[777funk]

How do the fuel supply systems work with these engines? I've heard someone say that the tanks are pressurized. Is this true?

I know my current Force 125 has a diaphragm fuel pump on the side of the block that draws fuel from the tank and pressurizes it to fill the carb bowls. Are the OMC engines different? Are there different fuel systems used from the 50's through to the 80's or are they all pretty similar?

Could I run an OMC engine from a small container of fuel for diagnostics? When I was troubleshooting I ran my Force from a quart can. A 125 HP will suck through a quart pretty quickly!!! even at idle. I was surprised at what a guzzler it is. Curious how the OMC fuel systems work.

thanks in advance.

 

[racerone]

You operate the primer button on those old tanks.----That fills the carburetor with fuel.---Once the motor starts it directs crankcase compression into the tank.----Air goes into the tank untill crankcase pressure is on the fuel.--Then fuel flows to the carburetor.------Crankcase pumps air into the tank as fuel leaves the tank.---A very reliable and safe system.

 

[pro-crastinator]

Are we talking about the pressurized tank systems - that were used with the old classics thru 1950 something? (not sure last year used)
Note this system was also used by mercury in the early days as well. Not a Johnson / Evinrude exclusive.

 

[777funk]

Thanks racerone. That's what I was looking to find. And yes Pro-crastinator, I was curious about those units. Looks like 1950-1960 OMC approximately. They switched to fuel pumps after this.

 

[racerone]

Those pressure tanks were very good and reliable !---Rather have one of those than the plastic junk made today !!

 

[mla2ofus]

My '54 15HP 'Rude has the pressurized tank and I love it. When I put away for the winter I siphon all the gas out then pour in the amount of 2 stroke oil for 6 gal to prevent rust thru the winter. In the spring I dump 6 gal of gas in it and we're ready to go.
Mike