Pontoon Boat & Deck Boat Forum

I bent the shit out if my 15x13 3/4 3 blade over the weekend, performance wise it was pretty good running mid 20's at 5000rpm on a 25 Crest with a 125 Mariner. I want to try a merc 4 blade 13x13.8. Is this a good idea or should I just stick with a new 3 blade? Thanks

Sixshooter44 wrote:I bent the shit out if my 15x13 3/4 3 blade over the weekend, performance wise it was pretty good running mid 20's at 5000rpm on a 25 Crest with a 125 Mariner. I want to try a merc 4 blade 13x13.8. Is this a good idea or should I just stick with a new 3 blade? Thanks

Depends... Do you know what is the recommended wide open throttle RPM for your Mariner?

Lets double check your numbers first... The Mercury 4-Blade is a Spitfire right? Well then it is a 13.8" diameter and 13" pitch. What is your blade a 13.75" diameter by 15" pitch? Generally when switching from 3-blade to 4-blade you want to drop a little on the diameter. But this is a fairly close match and if we got your numbers correct a 13" pitch should allow you another 400 RPM... 4-Blade props generally cost you a tiny bit of speed but they bite the water better and turn better with less blow out.

Max rpm is like 5100 I believe, it's a 96 model. I don't spend a bunch of time at max throttle, mostly cruise between 3000-4000rpm.