How to trial props?

[superbenk]

I'd like to experiment with a different prop, but it seems everywhere you can buy one online they are non-returnable once they hit the water. I'm not really near the water or any marinas with a service shop so how can I go about trialing different props? I'm on the fence over better hole shot or more top end so I'd like to try both to see which I like better.

 

[Sea Rider]

Assume you're not satidfied with your boat/engine combo ? To play with props need to go for a wot spin with lightly loaded boat on flat calm, no wind water conditions and check max rpm achieved. Then will know if under or over propped and go from there selecting the best pitch to maximize engine performance. Usually 150-200 +,- per 1 pitch change.

Good Samaritans with a full trunk of spare props to trial freely are near impossible to find.

Happy Boating

 

[superbenk]

I figured as much Here's what I have & I'm open to suggestions one way or the other. I have a 2008 Four Winns Horizon 200 with carbed 5.0L & Alpha 1 Gen 2. With just myself in the boat, 1/2 tank of gas & light chop I get around 48mph according to my iPhone (on a lake with no currents) at around 4700-4800 rpm. According to the brochure I *should* get ~53-54 so I'm a little disappointed there, but it's tolerable. With 3 kids & my wife it drops down to around 43 @ 4500 rpm. I'd like to achieve top speed but I've also been reading 4 blades can make things smoother at low speeds & cruising. I should get a spare prop so I'm considering options to squeeze out a touch more performance as well. We normally cruise but will sometimes tube.

 

[superbenk]

Current prop is 14.25x21" 3-blade aluminum

 

[Sea Rider]

With family oriented load going 1 pitch down will put you back to around 4700 rpm if you been previously running at wot and achieving just 4500 rpm.. What's the max wot numbers factory stated for that engine.

You should have an extra prop to be spot on for other water activities like, pulling tubes, wakeboarding, skiing. Delivered props are just good for overall cruising.

Happy Boating

 

[jestor68]

Unless you have established a relationship with a dealer, they may not be willing to go out with you to test different props, and most likely would not be willing to lend out expensive props for you to try

Not having a dealer nearby; the best recourse is to check the Mercury prop selector to see what it recommends. I have found it to be pretty accurate(if accurate data is put in).

Some simple calculations using a 10% slip indicates your tach may not be reading right based on the speed you state.

 

[superbenk]

I'm not sure what you mean by establishing a relationship or not being a customer. Everywhere I read about prop sizing and buying new props says it's largely a "trial & error" thing to find the right prop & yet it seems no place makes it that easy to test different setups. So I'm just curious how others do the "trial & error" part without ending up with a pile if really expensive props that aren't exactly what they want. I get that builders do a good bit of research to ship the boat with a good all around prop but how does the owner tweak that performance without trying a few options? As for my boat, I realize it won't be factory new, but when I bought it last fall it only had 18 hrs on it. Everything runs great but since I would like a spare prop I thought I'd find something to squeeze a bit more performance out.

 

[ihearth2o]

I'm sure you've already started but do your research before you spend any money. Learn how props are designed and how prop characteristics will affect performance. You also need to decide what those performance goals are otherwise be prepared to have a lot of spare props. Once you have that figured out, If you can bankroll it, buy it and try it out. Try to find used or try buying aluminum as they will be friendlier on the wallet. Once you think you've got the right prop, sell the others off. It will probably add cost to the whole process but given your situation, you have to get creative.

 

[steelespike]

If we assume the tach is accurate and the gps is accurate using a 1.61 gear ratio we get 19% slip at 48 mph..
If we use a more typical 13% slip we get a little over 50 mph.
I believe some of the on line prop dealers will "rent" props for testing or a sizable deposit is required to assure you will buy when you find
your best prop.
Some things to check.Is the bottom clean and smooth?Is the throttle opening all the way?
Perhaps the present prop is not the original and is an inferior design substituted so the seller could keep his better performing prop.
If there is a prop shop in your area you might see if they can add some cup to the prop.
As far as 4 blades go the Merc. Spitfire 4 bld. is said to give 4 blade performance without sacrificing top end.
using your same 21 pitch.I've seen 2 independent tests with positive results.
You also might consider the Turning Point Hustler in the same pitch.The Hustler is said to deliver close to ss performance for the price of aluminum.
If you can't find a prop dealer that will let you test; if the prop isn't right put it on Craigs list or ebay at a slightly reduced price.

 

[superbenk]

Thanks for the info! I'm not sure what the factory RPM specs are, but I seem to remember reading a carbed 5.0L should run somewhere around 4600-4800 so it seems I'm pretty close there. Boat is immaculate (like new) so the bottom is spotless. Prop is what is spec'ed from the factory.

I'll check out the props you mentioned & maybe look into seeing if there are any shops locally that handle props. Like I said I'm not really close to any water so I'll have to look around. Overall I feel like I'm close, but it'd be great if I could get a touch more. I'll do more research.

 

[JaCrispy]

I'd be interested in your current prop if you decide to sell. As long as it fits a Alpha One.

 

[superbenk]

I'd be interested in your current prop if you decide to sell. As long as it fits a Alpha One.

Whatever I do I'll be keeping the current prop as a spare.