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  Prop choice for 90hp Yamaha on a Classic 16

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Author Topic:   Prop choice for 90hp Yamaha on a Classic 16
Chesapeake posted 04-10-2001 12:54 PM ET (US)   Profile for Chesapeake   Send Email to Chesapeake  
Through prior posts, I know many of you have added Yamaha 2-stroke 90s to your classic 16/17s. I would appreciate it if you could tell me SS prop choice was considered optimal after your own testing? Maybe this will save some time with my own dynamic testing of props. Thanks.

Bob

JimU posted 04-10-2001 03:01 PM ET (US)     Profile for JimU  Send Email to JimU     
My prop choice was a 15 pitch stilleto. Produces good hole shot and top speed of 42-44 per my gps.
triblet posted 04-10-2001 03:03 PM ET (US)     Profile for triblet  Send Email to triblet     
42-44 knots or MPH?

Chuck

compounder posted 04-10-2001 04:10 PM ET (US)     Profile for compounder  Send Email to compounder     
Bob, my C-90 is relatively new & I have not completely dialed it in yet. That said, the 17in pitch Michigan Wheel SS prop I now have is only turning up to 51-5200 rpm. I would like to get this up to 5500 as suggested and am thinking of trying a 15in pitch.

I have heard, but not confirmed, that Yamaha brand props come in even pitches rather than odd, so it seems that a 16in pitch might be worth a try.

When I have more data nailed down I will report it on this forum.

Joe

Chesapeake posted 04-10-2001 08:33 PM ET (US)     Profile for Chesapeake  Send Email to Chesapeake     
Thanks men. I have already paid for, but not taken delivery of motor and prop (what the heck am I waiting for?), but the suggestion to start with a Yamaha 16 SS is a good one.

I will humbly accept all other advise / opinions. Thanks, in advance.

Bob

JimU posted 04-11-2001 02:00 PM ET (US)     Profile for JimU  Send Email to JimU     
Miles Per Hour. JIM
JimU posted 04-11-2001 02:00 PM ET (US)     Profile for JimU  Send Email to JimU     
Miles Per Hour. JIM
Tartansailor posted 04-12-2001 06:38 PM ET (US)     Profile for Tartansailor  Send Email to Tartansailor     
My 17ft. Montauk sports a 90hp Yamaha 2 stroke, with an Aluminum 13X17 prop.
With 3 men weighing 670 lbs. plus a full 32 gal. gas tank, its a white knuckle ride at top end. I believe the advantage of an Aluminum prop is that it will break before the drive train, in the event of hitting a rock real hard. Not so with a SS prop.
compounder posted 04-12-2001 07:22 PM ET (US)     Profile for compounder  Send Email to compounder     
Tartansailor, I may be wrong, but I think you've just repeated an "old wives tale."

Modern props are mounted in a rubber (neoprene?) device to prevent damage to your lower unit when solid objects are struck.

I would be surprised if damage were to be more likely with SS than aluminum.

Joe

Tartansailor posted 04-12-2001 09:34 PM ET (US)     Profile for Tartansailor  Send Email to Tartansailor     
Hi Joe,
My 90 hp Yamaha was built in 91, and does not have a neoprene slip clutch. Wish I had one though.
Dick
lhg posted 04-12-2001 10:12 PM ET (US)     Profile for lhg    
Forty years ago, when Mercury invented the thru-hub exhaust propeller, they introduced the "Flo-Torque" rubber sleeved propeller hub, to protect the drive drain. Compounder is right, the aluminium thing is an old wives tale, except for a non-rubber splined prop (does anybody still make those?) Actually, aluminium props are much more likely to let you down if you hit something, because of their soft blades.

Now, Mercury has a new design, called a Flo-Torque II, which is a separate, slide in hub made of plastic splines. No more rubber.
This will shear to protect a drive train. It's easy to carry a spare sleeve/spline. Because of this, their props can now be used on any brand engine, simply by changing the center hub unit. It seems like a great idea, and makes props easier to sell and switch between engines. But the Dealers for the other brands of engines are never going to tell you this.

Lil Whaler Lover posted 04-12-2001 10:22 PM ET (US)     Profile for Lil Whaler Lover  Send Email to Lil Whaler Lover     
Let us not be so hasty to call the aluminum prop vs. stainless prop situation an old wives tale. During the summer of 1999, Maine lakes had very low water levels. Many boaters refused to acknowledge the situation and thus there were many unfortunate encounters with granite. We replaced or rebuilt at least 40 props during the summer. About 30 of them were aluminum and the other 10 were stainless. Out of this small sample, we had 4 bent prop shafts with Stainless props and none with aluminum. I have to conclude that the risk to the drive system is greater with a stainless prop than with aluminum.

This observation does hold true when the boating is done in soft bottom conditions and I have no idea how it compares when stumps or other wood is hit, but with granite around it has become very hard to sell stainless for use in Maine lakes.

I would like to see more comments on this issue. Dave

Lil Whaler Lover posted 04-13-2001 07:03 AM ET (US)     Profile for Lil Whaler Lover  Send Email to Lil Whaler Lover     
Woops, I meant to say does not hold true in soft bottom conditions. Apologies, Dave

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