Prop Questions

[Bow Guy]

I have a 73 Mercury 650 65 hp 3 cylinder and the motor was originally on a 15' Glastron ski boat when purchased new in 74.. The second owner of the motor put it on a 21' or 22' Lobster boat and changed the prop to what's on it now, it's a 3 blade and the only numbers on it are 2064 R 10.
The motor is on my 16' Smoker Craft Challenger Aluminum boat
Question:
# 1 Can anyone here decipher this number? to size & pitch ?
# 2 How would I select my length in the Michigan Wheel selection section as a 14' to 16' ( 12 Pitch) or a 16 to 17' (13 Pitch)
# 3 or am I good on what I have its in good shape the boat does 34 against the tide and current on the Hudson River
Thanks, Bow Guy!

 

[Sea Rider]

BG,

You should tach current prop you alone on a wot run while lightly loaded, check if inside factory wot rpm range for that OB, remove prop and take to a prop shop to have it measured, will know if in need to suit a better +, - pitch prop to opt performance maximizing a new prop on your current application..

Happy Boating

 

[steelespike]

With a gps you can tell what the current is And get a accurate wot speed.
What is the rpm at 34 mph? Is the speed by gps?
​ Did you look under the prop nut for numbers?

 

[Bow Guy]

Sorry for the dumb question, What is wot? I dont have a tack on the boat and the speed was by GPS

 

[David Young]

Wot = Wide Opened throttle

 

[Sea Rider]

If wanting to be spot on your boating activities, need to install a tach, speed is relative, wot rpm is all. Buy a cheap induction Hardline tach : https://www.hardlineproducts.com/pro...o-8-cylinders/

Follow installation instructions and report back both up/down river wot rpm runs. It's normal for OB to lose some top wot rpm while going up river, how much, will depend entirely on river's stream strenght and OB HP.

Happy Boating

 

[SkaterRace]

Installing a cheap tach will help you figure out the proping issue. You can buy them off amazon for less than $30.

 

[Bow Guy]

I guess I have to get a tach, thanks
here's a video of my first splash the other day after the boat restore