1970 Johnson 9.5 Gas Efficiency

[ugmold]

This summer with Gas Prices so crazy I decided to run my Johnson 4hp on my 12 ft Aluminum instead of the 9.5 (both 1970). I was startled at how efficient the the 4hp is compared to the 9.5 which I always thought used way too much gas, but ran well. And yes I realize the size difference, just seems way off.

 

[racerone]

Check / replace fuel pump diaphragm.-----Inspect float and float valve.-------Agreed the 9.5 is not very fuel efficient compare to a 1984 model 9.9 / 15 HP or a 4 stroke.-----But you can carry that 9.5 at about 60 lbs.

 

[909]

My old turtle used too much gas for it's size too. They're low compression motors that aren't exactly the most efficient.

But you can't beat the size, the way it folds up, and the weight as racerone mentioned.

A lot of pilots love this motor because its so light, and takes up almost no room.

 

[ugmold]

I think I put a new diaphragm in a few years back. And I do love the engine, it pushes the 12 ft aluminum along well. But I guess you guys just confirmed the fact that it a gas guzzler. Thanks

 

[Crosbyman]

thissummer I took out my turtle even if I loved it ...last year'S fishing trip kind of showed the ugly side of the 9.5hp (loves fuel)

at 7-8 $ cdn a gallon I decided to rig up a nice Merc 4hp phase maker ignition. After a good carb job , cleaned the point adjusted the idle limit screw it just ran and ran ...all day

I could not believe the difference after 3 days of lots of trolling I did not use more than about 2 gal.
I ended up reverting back to the DARK side

see before and afetr shots of my rig

 

[racerone]

Check the number / size of the high speed jet.----Possible someone opened it up to try and make a 15 HP out of it.

 

[ugmold]

Check the number / size of the high speed jet.----Possible someone opened it up to try and make a 15 HP out of it.

I have read about people putting a 15hp carb on a 9.5 which makes it a 15hp (don't know if that is true) but is the high speed jet the only difference? Any idea what size it should be for 9.5 and 15?

 

[racerone]

That model was NEVER offered as a 15 HP.---Only one carburetor ever offered.---------The newer 9.9 / 15 HP shared the same block.------There is the mistaken belief that you can make any 9.5 / 9.9 into a 15 with a bigger carburetor jet.------ 9.5 HP typically used a 0.049" orifice plug ( AKA jet )

 

[ugmold]

That clears that up. Thanks Racerone.