1957 Johnson 7.5

jimbobmt

Recruit
Joined
Jul 8, 2010
Messages
4
I am interested in some information on this motor.
First, I saw it yesterday, and what a beautiful outboard motor! It has NEVER BEEN RUN! The guy bought it from an old timer that had it in his garage and it has never been in the water. It even came with the original owners manual still in new condition. The model # is AD-11, Ser. # 1658935. Now for the tough stuff.... He didn't get the fuel tank and line, and it has a triple type connector. From what I can gather by reading the manual, one connection is for fuel, one for pressurizing the external fuel tank, and the connector lock.
He's been told that it can be converted to a dual type plug, but original is best on this "new" motor. Where could I find a tank and connection hose?

The next puzzle is the oil/fuel mix. In the manual it says "use a reputable outboard motor oil or regular SAE 30 grade automotive engine oil (not heavy duty)"....."Put 1 gallon of gas in a 4.25 gal. capacity tank and add 1 quart of oil and mix throughly. Fill the tank the rest of the way with fuel." "If smaller amounts are required, use 1/2 pint of oil to 1 gallon of gasoline"

So for this era, it's leaded gas and motor oil? How will unleaded gas act? Should we use lead additives? Is motor oil recommended because of the lack of outboard motor oil during that era? Would the ratio need to be changed using modern mix oil? The book says to "avoid premium gas due to the higher lead content".

I hope to be able to post a few pictures in the future, but I'm still trying to find out how to reduce the file size so it will attach. It's a beautiful motor!

Jimbobmt
 

turtles11756

Petty Officer 1st Class
Joined
Dec 5, 2007
Messages
260
Re: 1957 Johnson 7.5

old gas tanks for your motor are seen on ebay they have a small finger pump on the top of tank to build pressure / prime .you may find one that needs new gaskets or you can convert motor to fuel pump type tank .sure would like to see pics of your find. vintageoutboard.com for parts . it still has a hot spark ?
 

JB

Honorary Moderator Emeritus
Joined
Mar 25, 2001
Messages
45,907
Re: 1957 Johnson 7.5

The correct modern fuel mix for that engine is 1 Qt. TC-W3 rated outboard oil to 6 US Gallons 87 octane unleaded gas. That is a 24:1 ratio.
 

1stgenbird

Petty Officer 1st Class
Joined
Aug 5, 2009
Messages
397
Re: 1957 Johnson 7.5

You gotta post some pics of this motor. Sounds like quite a find.
When I was a kid in the '60s my older brother had a '57 7.5 Seahorse that he really pampered and that was a sweet outboard.

There is a seller on ebay that sells the restored pressure tanks for Evinrudes and Johnsons. They go for about $100 and look great.
 

bktheking

Vice Admiral
Joined
Jul 29, 2008
Messages
5,057
Re: 1957 Johnson 7.5

Tanks aren't hard to find, I've got 2 in my garage, one i've never even tried. Don't convert it IMO, if the motor is all original find a restored tank as suggested off ebay and post pics!
 

1946Zephyr

Vice Admiral
Joined
Oct 21, 2008
Messages
5,556
Re: 1957 Johnson 7.5

please oh please oh please let's see some pics of this beauty.:D:D
 

Happy_Jack

Seaman Apprentice
Joined
Aug 13, 2009
Messages
41
Re: 1957 Johnson 7.5

Hi JimbobMT,

Sounds like a nice find.

If it has not been run, you can expect to need to remove the flywheel to replace the original (now definitely cracked) coils, clean and reset the points, check the spark plugs (Champion j6j if original, j6c to replace) then remove the carb & disassemble it, clean it out, and re-assemble with a rebuild kit, replace engine side fuel lines (3/16") it will definitely need a new impeller (powerhead must be removed to do this) and you should change the gear oil in the lower unit. Lubricate all the linkages, get a good (not contaminated) 2 line pressure tank, hose and fitting, fill it with a fresh mix of 24:1 oil, prime the carb with the button on the tank, adjust the high & low speed needles, and let it rip (in a bucket of water covering over the waterpump of course)

If you decide to do all of that, you should have a good running motor there, PLEASE take care when working on it not to scratch the original paint, it is only original once...
 
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