Testing new prop suggestions

[lake_effect]

Spoke with a local prop shop (Green Bay) and they suggested I buy an aluminum version of a prop they think should work before I drop a lot more on a stainless one and they should be able to tell what I need of the numbers I get with that one. Has anyone ever done that before? I'm a younger guy and don't have anyone with stainless props I can borrow and test run.

I have a 19' Mirrocraft Aggressor exp with a 08 Optimax 150. Getting 45 mph and 5000 rpm with the stock 19p black max. Not concerned about top end, was looking at 15 and 17p 4 blades. Any input is much appreciated.

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[Waxy]

Originally Posted by lake_effect

Spoke with a local prop shop (Green Bay) and they suggested I buy an aluminum version of a prop they think should work before I drop a lot more on a stainless one and they should be able to tell what I need of the numbers I get with that one. Has anyone ever done that before? I'm a younger guy and don't have anyone with stainless props I can borrow and test run.

I have a 19' Mirrocraft Aggressor exp with a 08 Optimax 150. Getting 45 mph and 5000 rpm with the stock 19p black max. Not concerned about top end, was looking at 15 and 17p 4 blades. Any input is much appreciated.

In my opinion, and it's worth exactly what you're paying for it, I don't think that prop shop is giving you the best advice, I wouldn't do that. You'd be comparing apples and oranges, and potentially be left with a prop you don't need or want.

I don't think you can get a really good idea of how a stainless prop will perform and get the data you need to make the right choice by running an aluminum. I would look for a different prop shop that will let you test a couple stainless props before you buy, or look to spend the money you'd spend buying that aluminum on shipping costs for a couple stainless props.

Waxy

[Kouki7]

I had access to a few props and this is how i organized the data when I was trying to sort what prop I wanted to run 90% of the time on the boat.

[Ltrain]

Originally Posted by Kouki7

I had access to a few props and this is how i organized the data when I was trying to sort what prop I wanted to run 90% of the time on the boat.

Very thorough and an excellent way to get a proper assessment. I did something similar but not as extensive. I limited my categories to rpm and speed at wot, speed and fuel burn at 4k rpm , paid attention to ease of planing and ease of raising the bow. Wish i could of seen your tables to use as a template. Very nicely done

[Kouki7]

Thanks! It was a bit of work, but was trying to gather both data for myself, and for others to have an idea of before they drop 600-700 on a SS prop.

Lake_Effect - One thing to note on aluminum props is they have the ability to flex. A 150 Optimax being a 2 stroke will have torque which can flex those blades more so than a 4 stroke, I would question comparisons being made between an aluminum prop to Stainless steel. I’m not that smart though to prop world, so maybe your dealer understands this and has a formula to account for that.

[DW]

Before you do serious prop analysis and selection make sure your motor height is correct. Outboards are frequently too low, and if so, you can not get optimum performance or optimum prop selection.

You can get aluminum props for $100 to 150 on line so experimenting with cheap aluminum props is an economic way to find the best final prop selection.Generally, pitch reduction is 1” when transitioning from aluminum to SS.

Since you are already seeing 45 mph you are already close.

[lake_effect]

Thanks for the help guys. I wasn't sold on buying multiple aluminum props so they could get close and then buy a stainless one as well. I am running about 250 rpms low of acceptable range and 750 low of max. Looks like I can go down to a 17 or even a 15 but that may be too low. Had the kids out tubing for my son's birthday tonight and I had to be going 20 to hold plane and that's higher than I'd like. I also get cavitation on tight corners.

As far as motor height I could drop it down 1 more set of holes but I'd like to not start messing with that. I'm going to watch out for a used high five, trophy plus or rev 4 17p and see what I can find and teat them out. Thanks again guys.



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[Snowking]

Just so you know rpm wise. Normally going to a four blade 17 pitch ends up close to what rpms you would have with a 19 pitch stainless three blade. If anything I would try raising the motor up. Not lowering it even deeper. The four blades props are known for being able to run the motor up higher.

[lake_effect]

My current prop is a 19p aluminum. I wasn't planning to lower it, just stating where it was for reference. Like I said i am going to look for a used 17p trophy plus, rev 4 or high 5 to start and see how it runs and then possibly look at raising it one set of holes.

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If it’s a prop shop, I’d think they loan you one, or several, to try. Several years ago my dealer happily supplied me with 3 to try.