I need a little basic prop info

[thunderroad]

I've got a 69 Formula 19' w/160 Mercruiser. My current prop is a 19P. WOT is 45-4700..but I very rarely run it there. Getting a skier up is no problem. Top end is around 35 if you can trust the 37 year old speedometer. The only thing that seems a little weird about the setup is that from 4000 up to WOT I can't tell any difference in top end speed. My question is.....I rarely pull skiers, mainly the boat is used for cruising. The majority of the time there are only two people in the boat. What pitch prop would be best for fuel economy and cruising or is the one I have as good as it's gonna get? Would, say, a 21P give better economy and still not strain the engine?...or am I thinking just backwards on the pitch?

 

[walleyehed]

Re: I need a little basic prop info

Prop design is a factor to take into account as well.
We want to stay near the top of the RPM range, or let's say from the middle up on an I/O or inboard.
What model of prop are you running now, and what is recommended WOT range?

 

[thunderroad]

Re: I need a little basic prop info

I don't know about design but it just looks like a basic 3 blade prop. The number on one of them is 48 58422 19.
The number on the other is 48 58422A1 19P. I can' t tell any difference in the two, either in looks or performance. I've been told that 45-4700 is the correct WOT range for my unit.

 

[deejaycee_2000]

Re: I need a little basic prop info

They are both 19 pitch so they would perform the same ... a 21 pitch would give you more speed, but less power on a pullaway, but a little more fuel economic on constant rpm ...

 

[thunderroad]

Re: I need a little basic prop info

Thanks....that's what I was wondering about. I really don't need a lot of quick power. I might spring for a 21 and see how it works. I suppose I could always sell it on ebay if I don't like it.

 

[walleyehed]

Re: I need a little basic prop info

"They are both 19 pitch so they would perform the same"...

This is the most mis-understood subject about props...
a 19P is not the same as X-brand 19P vs. Y-brand 19P.
I have a 23 Turbo that will out-run most 24's and some 25's at the same RPM.
You must understand the design before "assuming" any pitch in any manufacture will run the same...
I don't know what happened to my prop-test results from the other forum, but the 40-some props I ran on that series proves it.