Would another prop do any better than this?

83Evinrude

Petty Officer 1st Class
Joined
Sep 3, 2008
Messages
290
While testing an in hull depth sounder transducer location I also used a GPS to verify our WOT speed.

At an outside temp of 70deg I was able to trim out to a max speed of 53mph while running 4950rpm. Prop is a like new Michigan Wheel 14 & 1/4" x 21" Aluminum. The test lake is 915ft above sea level.

The boat is a 2004 Glastron SX 195 with a VP 5.0GL engine and two barrel carb rated at 220hp. Volvo lists the WOT rpm range at 4400-4800rpm. The engine has a fresh fuel filter and new spark plugs. The VP SX outdrive has a ratio of 1.60

Glastron lists the boat as weighing 2550lbs with my engine, length at 18' 7", beam at 90 3/4" and transom deadrise at 21 deg. Max hp for this boat was a VP 5.0Gxi at 270hp. This is a bowrider runabout and does not have any planning aids (outdrive fin or trim tabs).

On board at the time of the test were my wife and I for 315lbs, 28gal of fuel and and gear estimated at 100-150lbs.

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The boat is used for cruising, skiing, tubing and recently a bit of wake boarding. Usual load would be anywhere from two to six passengers. The boat has a nice holeshot and will go from in gear to 30mph in approx 5 seconds. Single slalom skiers come up very quickly and also pulls two adult tubers with ease.

I'm a bit over the max recommended rpm with a light load and was wondering if a better prop might improve things a bit. I'm thinking about one of the following options.

1. A Stainless 3 blade 14 & 1/4" x 21", perhaps a Stiletto Advantage II. Would this prop give a couple more miles per hour and preserve the current holeshot? Would cruise economy improve at all?

2. A Stainless 4 blade, perhaps a Stiletto Bay Pro 14 & 1/4" x 20? How much better holeshot should I expect and if I'm going to lose top end, how much? Would mid range cruising economy improve? If this isn't the right pitch for a four blade, what would be correct? Other comments on what to expect going from my current prop to a 4-Blade?

Any other prop type or pitch suggestions would be greatly appreciated. I would prefer a competitively priced Stainless model. I would not want to lose any holeshot, and would prefer not to lose top end as I see this as cruising economy.

Thanks.
 

Dhadley

Supreme Mariner
Joined
Feb 4, 2001
Messages
16,978
Re: Would another prop do any better than this?

Either prop will probably do better than what you have especially if you need to pull the rpm down a tad. The Bay Pro prop you're looking at is a good choice but it's a 14" diameter, not 14 1/4". The 14" is a Bay Pro II, the 14 1/4" is a Bay Pro III. The BP II is more suited for stern drives, the BP III is aimed more at outboards or higher X dimension applications. I think you'll like either the 3 or 4 blade Stiletto.
 

83Evinrude

Petty Officer 1st Class
Joined
Sep 3, 2008
Messages
290
Re: Would another prop do any better than this?

Either prop will probably do better than what you have especially if you need to pull the rpm down a tad.

Thanks for the response, I just plugged my figures into a prop calculator and 4950rpm at 1.6 ratio and 53mph works out to about 13.8% slip.

Is this about right, good or bad? Will a good stainless prop have less slip than I'm getting now due to better blade cupping?
 

hwsiii

Commander
Joined
Jan 25, 2009
Messages
2,639
Re: Would another prop do any better than this?

For the vessel you have that is high, you should be around 8 to 10% in my opinion.


H
 

83Evinrude

Petty Officer 1st Class
Joined
Sep 3, 2008
Messages
290
Re: Would another prop do any better than this?

For the vessel you have that is high, you should be around 8 to 10% in my opinion. H

If I was trimmed a bit too high could that account for slippage being a bit high? Prop not not hooking up well? What would cause slippage to be on the high side and what can be done if anything to lower it?
 

hwsiii

Commander
Joined
Jan 25, 2009
Messages
2,639
Re: Would another prop do any better than this?

Yes, that ould ause it. And buying the prop Dhadley reommended would ure it.


H
 
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