Propper prop for an 18 ?

[Sagbay32]

Just bought a 95 18 with 350 mag, and was wondering what prop is best. It has a michigan wheel on it now. I think it is a 24 x 14 and5/8. The boat ran around 63 non gps. Any info appreciated.

Thanks
Mike in White Lake

[Varyak]

Mirage 23 Plus, will get you where you want to be.

Mark

[Formula Jr]

Sagbay32, spend some time looking at the old posts. There's gold there.

[Ranman]

The answer depends on the ratio of your drive. My 350MAG Bravo One has a 1.65:1 ratio and thus requires a 25P Mirage Plus. If you have a 1.5:1 drive the 23P Mirage Plus is the ticket. You might also try a 23P Vengeance if you get the opportunity.

[Sagbay32]

How do I figure out the drive ratio on the '95 alpha?

[Formula Jr]

spin you engine one rev and see how many times the prop spins.
Engine is always 1 spin.
then you get the ratio. Engine 1:Prop 1.98, Ratio 1:1.98

[Tom on Lanier]

Or, you can read the ratio on the side of the outdrive. Rather inconspicuous but, if you look carefully, you should find, stamped in the Mercruiser decal, a small set of numbers like 1.5:1 or 1.65:1 or some such thing. If you have the Mercruiser owners manual that came with the boat, it is in there also. That is assuming the drive is what came with the boat originally.
You can definitely improve by changing from the Michigan wheel. The Mercury Mirage Plus is very good. The Turbo works well for me. Smaller diameter, more pitch = more speed, less chine walking. http://www.donzi.net/ubb/smile.gif

------------------
Tom
"Tomahawk"

[Sagbay32]

If I do choose the Mirage 23p for example what should I expect for numbers? I am new to this and don't have a full grasp on pitch vs. chine walk etc.
Also:
1. Where to get a good deal on a new prop?
2. Can I run an aluminum prop for these low water inland lakes? I was told I would only lose performance out of the hole.

Thanks again for the education
Mike

[Ranman]

My take on aluminum vs. SS

Aluminum - Because it is softer, the lobes of the prop must be made thicker compared to SS. Since the lobes must be thicker, they must slice through or split more water. This will cost you in top end (around 1-3 mph). Since aluminum is soft it gives or flexes. This is good when you hit something in the water as the aluminum prop takes the hit and is inexpensive to fix compared to SS. Aluminum is relativly cheap but not considered a real high performance prop. Aluminum props most likely flex on hard take-offs, but this may actually improve holeshot performance vs a SS since the flex will reduce pitch. Aluminum probably flexes at top end due to high stress/load etc.. again costing you mph.

Stainless Steel - First the props are much prettier. SS props can have thinner lobes and be just as strong as aluminum and thus can slice through the water more efficiently gaining you top end improvements. SS will not flex as much and thus holds its shape under more severe conditions which means more consistant performance. SS props are more resilliant to minor bumps and nicks than aluminum but if you really whack something, it could mean trouble.

Bottom line is if you want to maximize performance, SS is the only way to go. If you 're really worried about shallow water, aluminum may be a necessary sacrifice. Don't forget that you can always use both. Your best bet is to get a GPS and a couple of different props to try out and see which one works best for you. Fortunately, many of us have very similar combinations to yours and so the advice gained here is priceless. My bet is that if you have a 1.5:1 drive the 23P Mirage Plus will be your winner at the 66-68 mph range. Let us know how it turns out.

[Riley]

Mike, which Michigan Wheel prop are you running right now, and at what rpm? The Michigan Wheel Ballistic is a pretty good prop with a lot of hull lift. However, if you have the 1.5 ratio I think 24" is just too much pitch.

The Mirage 23 would put you in the ball park, but I'd also try a Laser II in either 21" or 23" pitch. I'd avoid an aluminum prop at all costs, just be careful where you do your boating.

As far as speed goes, I think Ranman might be a bit optimistic in his 66-68 mph estimate. I'd say you have a pretty strong running 350 Mag (270 hp)if you can get an honest 63-65 mph gps reading. Let us know how it works out!

[Ranman]

Sorry about the speed post. My 350MAG is 300hp and I gps around 67. If the '95 350MAG has less HP then the speed would obviously be less.