Prop size? 115optimax?

Post by **1lastcast** » Thu Aug 13, 2009 5:10 pm

Hey guys. Im looking for some help with selecting a stainless prop to replace my stock alum.

Boat is a 2007 Legend xcal 18ft with a 115 mercury optimax engine. Prop is 13x19 pitch.

Im looking for a little more hole shot when pulling a tub.

I have my eye on a 17p ss trophy prop 4 blade? But I dont want to push the RPMs to high on my motor? what are you guys with ss props running in terms of pitch?

Post by **CNs** » Thu Aug 13, 2009 6:34 pm

Go to this site

it s the mercury prop selector

http://appcenter.mercurymarine.com/propSelector/home.do

Max rpm for optis is usually 5750

Post by **1lastcast** » Thu Aug 13, 2009 8:17 pm

Thanks I have taken a look at Mercurys prop selection website. It is very helpful. however it gives me many options. So I thought I would ask others with motors like mine for there input

Im leaning towards a 4 blade 17p at the moment. My merc manual states that a 4 blade prop will lower the rpm from 50-100rpms. It also states that for every +1 in pitch I will decrease up to 200rpms. Every -1 in pitch will increase rpms up to 200.

I have to check my WOT rpms this weekend. Im sure I was running 5200rpms at WOT. So my math tells me going from a 3 blade to 4 blade would give me 5100rpms + -2 pitch (400)rpms = 5500rpms.

Post by **Mick** » Fri Aug 14, 2009 6:56 am

[quote="1lastcast"]I have to check my WOT rpms this weekend. Im sure I was running 5200rpms at WOT. So my math tells me going from a 3 blade to 4 blade would give me 5100rpms + -2 pitch (400)rpms = 5500rpms.[/quote]

out of curiosity, why is your WOT RPM so low?

I have a 115 opti on a similar sized boat to your legend. My WOT RPM is roughly 5600. I get out of the hole quickly and run very welll at WOT. And I pull a tube around with the kids and that works fine as well. I also have a standard Merc 19 pitch alum prop. Your 19 pitch prop should enable that engine to run at much higher RPMs at WOT. I would try to resolve that issue before looking for a new prop.

Mick

Post by **1lastcast** » Fri Aug 14, 2009 7:00 am

Thanks Mike.

Maybe its a issiue with my tach? What is your TOP speed? Im reaching 41mph GPS.

Post by **Luke** » Sat Aug 15, 2009 10:56 pm

I have a 178SC SE Princecraft with a 2006 115 optimax. I run a 13.25 diameter by 17inch pitch aluminum prop. WOT RPM is 5650, top speed 43mph (gps). Good hole shot when pulling the kids on the tubes. I borrowed and tried a Stainless Steel 17p 3 blade and there was no difference in performance. I have been told by two separate marinas that the aluminum prop is sufficient for the 115 due to the motor not being strong enough to flex it.

Post by **1lastcast** » Sun Aug 16, 2009 4:59 pm

OK, Just got in from the lake. What a great weekend to be on the water

And the fishing....well at least the weather was nice. lol

Anyway. WOT 5400rpm with proper trim. 2 people on board.

43mph on gps max. flat clam seas.

That works for me