Propeller Replacement 1973 65hp. Johnson

[Duck Heaven]

Hi Group!
I just recently purchased a 1973 Rinker Runabout/Tri-Hull with a 1973 65hp. Johnson. Currently, the boat out-of-the-hole is quite slow and at top end may only acheive 23-27 mph. I've been told the existing prop is generally used for trolling. There are no manufacturing names on the prop ... other than the number 2020. I'am confident ... the prop has been changed many times over the years and there is no-way to identify if the existing prop was the correct choice to begin with. I want to replace the existing aluminum propeller with a stainless steel. What diameter and pitch would be a good choice for overall performance? Thank You!

"Doc"

 

[WillyBWright]

Re: Propeller Replacement 1973 65hp. Johnson

Make sure your motor is running on all three cylinders first. Low pitch props give great holeshot and slow speed. High pitch props give lousy holeshot and high speed. Powerheads not running well give lousy holeshot and slow speed.

 

[Duck Heaven]

Re: Propeller Replacement 1973 65hp. Johnson

"Make sure your motor is running on all three cylinders first."

Willy B. Thank You for sharing your thoughts!

Yes! The motor is running nice and smoothe on all three cylinders ... and purrs like a kitten. This boat and motor set-up was purchased NEW and owned by only the one owner ... who unfortunately is now deceased. Decendants have little to no input on the history but were eager to share that the engine was always properly fogged while put-up over the winter months and plugs and lower unit gear lube checked frequently.

Willy B. I have considered taking the prop off and taking it in to a marine repair facility to have it properly measured so as to have a better understanding of the current props potential and usage.

Tell me sir ... does increasing the diameter of the prop from 12" to potentially a 13" necessarily provide additional "overall mph increase" or is changing the pitch more of a factor?

Thanks ...