1956 Evinrude 7.5 Fuel conversion

[spider1939]

Has anyone out there done a conversion from the 2 line pressurized fuel system to the single line with a fuel pump. I was wondering if this is a difficult thing to do , because I have read there is some safety issues with the pressurized system so hopefully someone can let me know how this is done and if it is very expensive. Thanks

 

[wbeaton]

Re: 1956 Evinrude 7.5 Fuel conversion

Don't believe the hype. Pressure tanks are fine. Most of us that run 1950's OMC's still use them. Also, you devalue your motor when you convert them.

 

[tashasdaddy]

Re: 1956 Evinrude 7.5 Fuel conversion

if you have a good pressure tank, it's not worth the cost. around $100 as long as you don't screw up. i did my 1958 35 hp, but i only had 1 tank, and need more tanks for long runs. the pressure tanks are in my opinion safer than the single line, the single line has a vent that fumes can escape. the pressure tank does not. it works on this principle, you pump the button to force gas to the carb, once the engine starts the engine pumps air into the tank to force fuel to the carb. there is not fuel pump. it is a totally closed system.

 

[R.Johnson]

Re: 1956 Evinrude 7.5 Fuel conversion

With the quality of the two line molded hose available today, leave that 2 line tank in the garage with the cap closed, and see what you get.

 

[klicknative]

Re: 1956 Evinrude 7.5 Fuel conversion

I was given a '57 7.5 with no fuel tank so I'd like to know how to covert it. I'm not real keen on having a pressurized 50 year old gas tank on my boat.

 

[Scaaty]

Re: 1956 Evinrude 7.5 Fuel conversion

Whens the last time ANYone heard of a old simple couple PSI P-tank going sky-high? The old deteriorated lines, in the old days, might have ruptured or been stomped on, sliced, cut, fish hooked, and let a touch of gas out...and the idiot was smoking a cigarette while checking.
The new line sold by Laings is just fine, or do the simple thing ..RUN 2 NEW HOSES OF TODAYS STANDARDS. They hold FUEL INJECTION PRESSURE. Sorry Johnson...your old wife's tales don't fly (yeah, I DO have some old Johnnys in the shed)

 

[Chinewalker]

Re: 1956 Evinrude 7.5 Fuel conversion

The old pressure tank, when cleaned up and rebuilt with new hose, o-rings, etc. (kits available from several sources) are just as safe and reliable as a single line with a fuel pump.

Ever opened one of those steel single line fuel tanks on a hot day? Ever seen what happens to one of those plastic tanks on a hot day with the vent closed? They get just as pressurized as the pressure tanks! If you've got a bad o-ring or hose on one of those, you'll spill just as much fuel...

- Scott

 

[BoatBuoy]

Re: 1956 Evinrude 7.5 Fuel conversion

Johnson, I just "re-hosed" a 2-line tank last week. It's been sitting in the sun at over 90 degrees several days with no problem.

 

[tashasdaddy]

Re: 1956 Evinrude 7.5 Fuel conversion

if it were me, and i just did a conversion, i would go to ebay and find a 2 line tank. it will be cheaper than the conversion. and 1 missed drilled hole and the engine could be toast, or having to by another one for replacement parts.

this is my 35 hp. it involves removing the bypass cover on the side of the engine, which you will have to replace the gasket. drill out the center hole, and drilling and tapping the 2 outer holes. buying the pump and gasket, new fuel connector and fuel lines. plugging air line on the motor.
not exactly sure on the 7.5hp but would be similar, i think. FR would know.

 

[spider1939]

Re: 1956 Evinrude 7.5 Fuel conversion

Thanks so much for all the replies. Its great to be able t get so much help in a short span of time. Thanks to all.

 

[F_R]

Re: 1956 Evinrude 7.5 Fuel conversion

The problem is that the 7.5 was never offered with a fuel pump, so therefor there is no bypass cover with the fuel pump mounting feature. That is not to say that you cannot make an adapter plate. If you are skilled enough to do that, you already know how.

 

[R.Johnson]

Re: 1956 Evinrude 7.5 Fuel conversion

When I was a school kid, a friend had a 10 HP johnson with a pressurized tank. The fuel hose under the hood, going from connector to carb. broke. By the time the fire was out, the aluminum hood was dripping in the river. The tank itself won't over pressurize, it has a check valve to prevent that. If that pressure tank fail's on the water, who's going to have one to help you out. I would not want to bet why OMC stopped threre use, more than one reason would be my guess. I won't argue that they will work alright, they do! I just feel that a fuel pump is better for reliability.

 

[klicknative]

Re: 1956 Evinrude 7.5 Fuel conversion

Thanks guys, I'm not going going to have any problem mounting it. My plan is to build a bracket and mount it on the port side of the engine. I need to know where to put the pulse line conection on the engine. I assume on the intake manifold/plate. Is there a boss cast into it where I can drill and tap for 1/8" NPT? Another reason I want to convert is so I can use a 3 gallon tank to save a little space on the boat. I'm going to use this motor as a kicker on my '63 Fiberform 15'. I need a second fuel tank because this motor needs 24:1 mix while my main ('69 40HP Lark) runs 50:1.

 

[wbeaton]

Re: 1956 Evinrude 7.5 Fuel conversion

"I just feel that a fuel pump is better for reliability."

+50 years on my tanks and motors. I call that reliability. I do agree that a fuel pump is a better system in principal, but not much. In the end, they both get fuel to the carburetor in an effcient and reliable manner.

Also, broken/leaking fuel lines can happen on any motor. Its an interesting story, but not fair to blame the pressure tank.

Klicknative, if you have to carry a separate tank for your 7.5 hp anyway why does it matter if its a pressure tank or not? I could understand it if you wanted to share one tank.

 

[Chinewalker]

Re: 1956 Evinrude 7.5 Fuel conversion

Plus, having the dual line tank assures that you ALWAYS have the motor hooked up to the 24:1 mixed tank and not the 50:1...

- Scott

 

[jdkessel]

Re: 1956 Evinrude 7.5 Fuel conversion

Here is a link I came across when shearching for double line tank repair kits. It mentions the 7.5 but I dont know if it will be of assistance to you.

http://www.outboard-boat-motor-repa...tboard Boat Motor/Pressureized Fuel Tanks.htm

 

[klicknative]

Re: 1956 Evinrude 7.5 Fuel conversion

Chinewalker, I don't have the tank for this motor. I do see your point about crossing fuel lines. I'll mark the 24:1 line with some red electrical tape to ID it. I'd rather buy a new tank than take my chances with a used pressure tank that may have rust, pinholes, weak seams, ect.

 

[klicknative]

Re: 1956 Evinrude 7.5 Fuel conversion

I just read JD's link so now I see how to get a pulse signal from the existing fitting. I'm going to try to find a core plug to fit the hole instead of a rubber cap. I was planning to use a Mikuni style pump and fabricating the braket to use the case screws to hold it to the motor. I'll keep the old parts I take off so it can be returned to orginal.

 

[wbeaton]

Re: 1956 Evinrude 7.5 Fuel conversion

"I'll keep the old parts I take off so it can be returned to orginal." - thanks.

 

[BoatBuoy]

Re: 1956 Evinrude 7.5 Fuel conversion

I read jdkessel's link also, and I think the author was sniffing his own tank. There are inaccuracies as well as imaginaries in the article. However, converting to a fuel pump is great if that's what floats your boat.