SS vs Aluminum specs.

[Mudbugger]

OK, so I'm ready for the tar and feather, equipment and brigade to arrive, as I don't have all the requested info that listed in the sticky. I'm ready for it, but here goes.

The boat in question is a 1985, Invader, 17 ft open bow runabout, sporting a 3.0/140 carburetted engine with an Alpha 1, Gen 1 outdrive and a 2 blade (was originally a 3 blade, but I modified that, on our last outing!) aluminum 14 X 19 prop.

The performance was acceptable as was, the engine would hit the lower end of the WOT, RPM range, at about 4200 RPM.

I've received conflicting suggestions, about changing from aluminum, one guy says go down 1 pitch size (17") the other says go up one pitch size (21"). Just coincidentally, each one happens to have a good used prop, that matches his suggestion! Go figure that!!

Anyway, obviously I'm new at this, and boating is a rather small part of my life, too many really pressing things, allow too little time and dollar$ for the fun things.

Any and all advice appreciated, I will accept the tar and feathers, as punishment for the missing info. Plus, the boat is presently about 750 miles from my present location.

TIA.

 

[QBhoy]

Your rpm are fairly low for what I’d expect from that rig and it’s likely gear ratio. Are you trimming up and or is there a chance the prop was in bad shape before the “modification” ?
I would naturally stick with a 19” for this set up.
As always. There is no real hard fixed rule around these things sometimes. Some set ups find that the rpm will increase at the top end with a good stainless (with same pitch as ally previously)...simply because the hull is lifted further out the water..giving less load and more speed/rpm.
depends on the prop too. If you throw a prop like just a bog standard vengeance on it. You’ll likely lose rpm...and often speed too.

 

[dingbat]

I have three props for my boat.

An aluminum Michigan Wheel 14x17 that I carry as a spare

A stainless Evinrude Offshore Renegade 14.25 x 17, 4 blade that I ran for 10 years

A stainless Mercury Enertia 15x15 that is currently on the boat

Three different sizes and two different materials yet all three met WOT rpm criteria and have similar top end speeds. The big difference between the three is how they perform under differing circumstances.

The only way to know for sure is to try them. See which one works best for you

 

[Texasmark]

How about this: http://boatpropellers.iboats.com/Mer...t_id=375185985

If I read the ad correctly the hub is part of the purchase price and this prop, like a lot of props today, has a removable hub.
This prop should get you up into your power band better, has excellent characteristics, similar to SS props other than blades aren't quite as thin, will give you a dazzling hole shot (getting up on plane) and hold the stern up better when cruising in the 20-25 mph range. SS prop would be 2-3x the price of this prop and these are tough alum. props. I have 4 of them currently and 2 SS props; not to fit your boat but brand/type.

 

[Mudbugger]

Thank you all for your suggestions and knowledge. I did go ahead and buy the 14 X 17, stainless, for $50.00, I figured that there was not much reason not to. It's in very nice shape.

I'm looking into the Hustler, 1730, 4 blade also. It will be several months before we return home and before boating season begins.

We're currently in Alabama, so I'll continue looking around, to see what may be available here, as the market appears to be more favorable here than back in Indiana.

 

[jimmbo]

What brand and Model is the SS prop you bought?

 

[Mudbugger]

jimmbo, it's marked Quicksilver, so that should be Mercury/Mercruiser, correct?

I also for a deal, on that Hustler 1730, new $86.00, delivered. I will have to purchase a hub kit at some point in the future.

Boating season is still a long way off.

 

[jimmbo]

$86 isn't a lot of Money, as you get to learn something about props.

TP is a Price Point prop. Some people swear by them, I tend to swear at them, as I have unboxed more than a few that had one of the blades that wasn't quite the same contour as the other 2 or 3.

Yes Quicksilver is Mercury's 3 Party Brand(to be sold at Retailers that aren't Mercury Dealers). Most Props are very close to, if not Identical to the Mercury Brand props

 

[Mudbugger]

Well, that TP Hustler arrived yesterday. I must admit, it is an unusual looking creature, with 2 distinctively different pairs of blades.

 

[Texasmark]

Well, that TP Hustler arrived yesterday. I must admit, it is an unusual looking creature, with 2 distinctively different pairs of blades.

Apparently that's the old design. The new design all blades are identical...both of the ones I recently purchased were of the new design. My take on the original design with 2 different blade patterns is that you setup 2 different resonances so you have vibrations at 2 different frequencies, remembering that Merc originally delivered production outboards with 2 bladed props for efficiency reasons (opinion) and finally realized that a 3 blade was a bit less efficient but ran quieter, and a 4 blade (symmetrical) even quieter. I said it before somewhere on this site that when I was running my '89 (sale year not year built) Ranger and 115 tower and Quicksilver Laser prop, when on the pad I could hear 2 distinct noises: The engine singing at 6k and the prop blades beating the water making a humming sound.

 

[Mudbugger]

Interesting, the page still shows it as a dual geometry prop. At any rate, it will be interesting come about May or June.

 

[Texasmark]

Interesting, the page still shows it as a dual geometry prop. At any rate, it will be interesting come about May or June.

I know it does. My guess is once fielded the vibrations caused them to look closer at the design and put both ideas into each blade, rather than every other blade. (opinion)