What's the right Prop Size?

[Kamalot]

Ordered a 23' NR Seahawk Outback with Yamaha F225, was told by a coworker that stock prop 14.25 X 20 would not be a good choice. He suggests 15.25 X 18 for my setup!!!

[WaterDog]

What are you looking for? Better hole shot, better top end?

Whoever your buying the boat from should water test it and give you the prop that matches the boat. I'd then get a SS and save the stock for a spare. When I had a prop, the difference between the SS and the Al in the same pitch was night and day.

[Metal Manipulator]

I asked a boat dealer once and he told me on my inboard that when you aplied the throttle out of the hole that your RPM should hit 4,000 or alittle above with a normal load in the boat. Of couse the best bet is to call the manufacture, or talk to a boat dealer or his mechanic.

[Kamalot]

I've done some research, and what I've come to realize this that this motor should top out at about 5800rpm at top speed. Which in my case should be around 50mph, and I was planning on SS Prop which makes it more important to get it right due to the $$ involved. So what I'd like to fine is somebody running this same motor on a simular hull and find out what RPM, MPH and Prop their running, to help deterime what might be right for me.

[SlabQuest]

Waterdog is right, find out the correct WOT range and water test. Every boat/motor is different.

[TWB]

Anchorpoint, the number one most important thing on an outboard is to not over rev it. So, you need to start there. If the maximum rpm for that engine is 5800, you need to be propped so that it does not turn up past 5800rpm when you have it wide open. When you get the right diameter prop, then you can start playing around with props with different pitch. As was said, you can change the pitch to affect your rpm, your top speed, and the hole shot.

Your dealer should be familiar enough with his product that he could recommend a prop to start out with. Most dealers have test props around that they will let you try to see what works best on your boat. Ask him.

Keep in mind that a prop shop can tweak a props pitch to fine tune your craft. Even if you buy one that is a little off, a good prop shop can usually get it dialed in.

The prop shops are another good source of info, and some of them have test props that you can use, if you are buying a new one from them.

[NorthRiverRick]

anchorpoint,

I've got that boat (21') and motor with a 14x19 aluminum prop. This was the standard that NR offered with my boat. The motor is hung on an outboard bracket BTW.

The Yami specs list WOT operating range at 5-6K rpm. They also recommend propping to result in a WOT in the top half of that range.

If you look at the performance bulletins on the Yami website, you'll see their choices of props on similar boats all result in 5800-6100 WOT RPM.

Mine runs up to 6100 RPM when trimmed out. I was considering a stainless prop at purchase but decided to stand pat with the standard. I'm currently thinking of going to the Yami 15.25x19 Saltwater series (stainless) prop. But...before I spend the big $$ I think I'll go to a place like Seattle-Propeller to get an expert opinion and computer calcs.

Another ifisher, gimmeumpqua, has the 22' that he re-propped to a stainless last summer. He'll give you some good info I'm sure.

Let me know if you need any other help spending money on your boat, I'm getting good at it!

Rick

[fish assassin]

Try the Michigan Wheel web site. They have a "prop-it-right" section that
asks all sorts of questions and then in about 10-14 days the come back to
you with the correct size wheel(s) for your ride.

Find it here: Prop-It-Right at Michiganwheel.com

Go to the data bar on the left and pick Outboard & Sterndrive Analysis. It's free
and they do it right.

-assAssin-

[Kamalot]

Hey NRRick,

When you're trimmed out and at 6100rpm, what is your MPH?

This info will help me calculate. I did check the Yamaha Site and had determined from there as you did that a 15.25 X 19 would probably work well!

Thanks Cory

[NorthRiverRick]

anchorpoint,

The boat does 53-54 mph depending on load. It has a pretty good hole shot as well. Certainly good enough for a fishing boat. :grin:

Rick

[NorthRiverRick]

fish assasin,

Thanks for the link. Seattle Propeller has a similar form to fill out for analysis. I think I'll do both and compare results/recommendations.

Regards,
Rick