prop on 40hp jhonson

[teelaw64]

looking at prop to get more rpm. theres a key way with no key and keyways on shaft is smaller then the one in prop. but theres a sherr pin though. as much as can find stamp on front hub says p j 40 looks like you could put bigger dia prop on. im not sure of pitch .1976 jhonson model 40 el 76r

 

[F_R]

Re: prop on 40hp jhonson

The keyway in the prop is not used for anything, it is used only for assembling the prop at the factory. PJ-40 is an aftermarket prop made by Michigan Wheel Company. I don't know the size offhand.

 

[Daviet]

Re: prop on 40hp jhonson

What RPM is the engine running now at wide open throttle?
I think the standard prop was 10 1/2 X 13, with 4 or 5 different sizes available.
You need to know what RPM you are turning now to guage what prop you need.

 

[teelaw64]

Re: prop on 40hp jhonson

What RPM is the engine running now at wide open throttle?
I think the standard prop was 10 1/2 X 13, with 4 or 5 different sizes available.
You need to know what RPM you are turning now to guage what prop you need.

well it dont go very fast gps shows 12mpr i don know rpm how do i check

 

[steelespike]

Re: prop on 40hp jhonson

If you read the stickies at the top of the page and get us all the info you have about the boat and motor.An induction tach like a Tinytach will get you the rpm.
If you have some sort of reasonable size/weight boat at 12 mph you have problems other than a prop.Do a compression check.Very likely you are running on one cylinder or throttle not opening all the way. Check the spark,observe the movement of the throttle.