oil:gas ratio 1957 Johnson Seahorse 7.5hp

[Medicman613]

Hey all,

I recently inherited a 1957 Johnson seahorse 7.5 outboard. I have the original manual that came with the motor and when I do the math works out to a 20:1 ratio gas to oil. After looking online I have seen anything from 16:1, 20:1, 25:1, and 50:1. What are people's recommendations? I called a local Marina and they suggested 50:1 with the new oils. Still not convinced!

Thanks

 

[bbstacker1]

No question oils are better today than in 1957. However the engine itself has not changed, it still has friction bearings, keep it at 16:1.

 

[racerone]

The 1957 model 7.5 hp is one sweet running motor if it has been properly maintained.--- It has plain bronze bushing and those need a good quantity of oil.---Stick with a 20:1 ratio here !!!-----If you do not know how old the waterpump impeller is you should consider installing a new one.

 

[Crosbyman]

great motor I have the evinrude version along side my 75 ETEC

converted it to pump and now burning xd-100 in it since I have a short trolling season .

xd-100 is nice ..no fumes to speak of ..no stinky smell biodegradable to !! and decarbs the motor

 

[boobie]

What gas oil ratio are you using in the 7.5 ??

 

[F_R]

That motor was shipped from the factory with a 4 gallon tank. It said right on the side of the tank, 1/2 pint of outboard oil per gallon of gas, or one quart of oil to a full tank. That's 16:1, not 20:1 or 24:1 or 50:1 or anything else. Believe it or don't believe it.

 

[Crosbyman]

4 us gallons is about 16 liters so 1 liter of o?l is 16/1 with xd-100 but.... it is pricy about 10$/L you can try AMSOIL synthetic but is is also pricy

 

[Vic.S]

1/2 pint per gallon is indeed 16:1


Perhaps the OP should tell us exactly what his manual says ....

 

[Medicman613]

Just at work now, I will post what the Manual said later. There was discrepancy between the manual and the gas tank however.

 

[racerone]

This is because they supplied / had different size tanks for motors !!----The 10 hp and larger came with a bigger tank , 5.5 and 7.5 hp models came with a smaller tank.------The larger motors with different bearing had a different ratio printed on the tank.--------The bigger tanks ended up with the smaller motors.-------------Use 20:1 on this motor today.

 

[boobie]

I was always told in service school that if it had bronze bushings to use 24:1. If it had full needle bearings you could use 50:1.

 

[Medicman613]

Here it is folks. Quoted directly from the original manual from 1957:

Pour 1 gallon of gas into mile master tank (3.2 gallon capacity). Add 1.5 pints of oil and mix thoroughly. Fill tank with gasoline. FOR EASE OF MEASUREMENT when mixing smaller quantities of fuel, mix 1/2 pint of oil per gallon of gasoline.

As per my math that is 20:1. Can sme one verify? Just started on this site and I like it already. You guys are so helpful and fast to reply!

 

[Vic.S]

Here it is folks. Quoted directly from the original manual from 1957:

Pour 1 gallon of gas into mile master tank (3.2 gallon capacity). Add 1.5 pints of oil and mix thoroughly. Fill tank with gasoline. FOR EASE OF MEASUREMENT when mixing smaller quantities of fuel, mix 1/2 pint of oil per gallon of gasoline.

As per my math that is 20:1. Can sme one verify? Just started on this site and I like it already. You guys are so helpful and fast to reply!

No its 16:1

1/2 pint to 1 gallon of gasoline is 16:1. Thats obvious ......8 pints in a gallon so 16 half pints in a gallon.

But for the instructions filling the tank.......

Tank holds 3.2 gallons total . Thats 25.6 pints. Youve put 1.5 pints of oil in there so there is only (25.6 - 1.5) pints of gasoline. Thats 24.1 pints ... call it 24 pints

24 : 1.5 is 16:1

sorry to take a full 1/4 hour to reply

Gone off this site again now ???

 

[nwcove]

Hey all,

I recently inherited a 1957 Johnson seahorse 7.5 outboard. I have the original manual that came with the motor and when I do the math works out to a 20:1 ratio gas to oil. After looking online I have seen anything from 16:1, 20:1, 25:1, and 50:1. What are people's recommendations? I called a local Marina and they suggested 50:1 with the new oils. Still not convinced!

Thanks

local marina suggested 50:1 ? do they sell motors? stick with 16:1 or you will be looking for one in a short time. follow factory specs whether you mix 30 wt or high end synthetic . jmo

 

[Medicman613]

Thanks all. If your ever in Ontario and see a big blue cloud of smoke Behind a boat it may very well be Me... 16:1 for the win.

 

[Vic.S]

Thanks all. If your ever in Ontario and see a big blue cloud of smoke Behind a boat it may very well be Me... 16:1 for the win.

16:1 is oily but most British Seagull engines ran on 10:1

I use one , but its a fairly late model which I have now converted (carb mod) to run on 25:1
When I first had it I used ordinary SAE 30 oil at 10:1 .........I'm sure 35 years later you can still see the smoke

Now then Ontario is Canada ... I thought you used litres not all these old gallons and pints.........

 

[Medicman613]

I do, but I have to make it easy for the crowd I'm asking questions too. Conversions on my end is easy

 

[Medicman613]

Well all. Today was the day for the great pull on the pull cord. Not a peep from the engine was made. I have already replaced the plugs which are sparking beautifully. I pulled the plugs aqnd there is no fuel in the cylinders. Upon closer inspection of the carburetor (the most likely culprit) I noticed some gunk built up in the float chamber. You know what that means! Carb is coming off...Anyone know any reputable dealers for carb rebuild kits?

 

[Medicman613]

Took the carb off, and it's clean as a whistle other than the glass float bowl that had a bit Of build up. Luckily no gaskets are damaged as they are made of thick rubber. Will try starting engine tomorrow.

 

[Crosbyman]

''If your ever in Ontario and see a big blue cloud of smoke Behind a boat it may very well be me........'''


After hearing that Hillbilly song about Ontario blackflies you should run 10/1

https://www.youtube.com/watch?v=qjLBXb1kgMo