Old Prop Size?

[estedman]

I took my old prop off since it needs to be replaced and I wanted to verify the size/pitch. I'm new to all of this so wanted to check first before ordering.

The only numbers I found were:
487952-17 inside the prob by the hub.
70-120-3c stamped outside by one of the blades.

I am I assuming that this is a 17 pitch prop?
I measured the Diameter at 14.5", if I measured it the right way.

I am looking at a 15.25" 15 pitch prop. I know the pitch drop should increase my rpm's, but what will the increase in Diameter do?

1990 Maxum 2500 Cruiser
5.0 Merc Alpha 1
Current WOT: 3900 rpm 32mph
Redline I think is 4400rpm.

Thanks!

 

[Texasmark]

Re: Old Prop Size?

What you are doing is looking at a prop capable of pushing a heavier load adequately. The larger diameter goes hand in hand with the lower pitch to provide added thrust for heavier loads.

One would expect speed to fall off a couple mph, and rpm's to increase 300-400, with a gutsier hole shot and better capacity to control the boat just above planing speed.........but you don't know what will really happen till you actually run it.

Mark

 

[estedman]

Re: Old Prop Size?

Thanks, thats what I was looking for, figured it would be a little trial and error.
So I'm reading the part # correctly, that the old one was a 17 pitch? The numbers were hard to read on the old prop.