25hp Merc 2s-What 4 Blade Prop Pitch?

3204 Views 10 Replies 4 Participants Last post by Rollbar, Jan 22, 2017

Rollbar

Discussion Starter · Jan 19, 2017 (Edited)

I have a 25hp Merc and currently it has a 13P 3 blade aluminum prop on it (2106R 13)(38x13P).
Problem: prop blow-out.
Transom is 16 1/8" tall and this motor is a short shaft which measures 17" from mount to cav plate-Not much room there in height/can't adjust down.
It blows out just before the boat planes and I back off it just a little to grab and then I can proceed to WOT which I run at 27mph loaded/2ppl.
Running rpm w/this prop is 5880-6k.
Given the OEM prop I have (listed above) what pitch would I need in a 4 blade aluminum prop?
I would like to stay w/aluminum and looking at the Solas or Hustler prop if possible.

Motor specs if needed:
Ser# 0D182388
GR: 2.25
Thanks again,

Link to boat pics if needed:
http://www.microskiff.com/threads/134-stumpnocker-skiff-tiller.41689/#post-326725

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Rollbar

Discussion Starter · #2 · Jan 21, 2017

Found this info and at the bottom of page 15-16 in reading this I can keep the same pitch as my 3 blade when converting to 4 blade and only lose maybe 100 rpm.
http://media.channelblade.com/boat_...s/dts/dealerlibraries/8441/copetipstricks.pdf

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Skiff Junky

· #3 · Jan 22, 2017

Full disclosure: This is my ad.

These props are left over from back in the day when I did this.

http://www.microskiff.com/threads/props-for-25hp-merc-2-stroke.37801/

The 4 blade 13p with extra cup should do the trick. If not, you most likely have a set up issue. Keep in mind, when I used to do this 50% was set up and 50% was prop.

Never was fond of Solas SS props as they were too unpredictable for me. That said, lots of people have claimed to have luck with them on this site.

If you go the aluminum route, you will need to find a shop that will cup it (properly) for you.

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