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  PROP size for 14' Dauntless w/50 hp

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Author Topic:   PROP size for 14' Dauntless w/50 hp
dghinseaford posted 04-20-2008 08:26 AM ET (US)   Profile for dghinseaford   Send Email to dghinseaford  
Hey Guys,I know that the common thought is a heavy Mercury 50 hp 4 stroke is not enough for the heavy 14' Dauntless.
That said, my Dad bought this new in '99 and that was the package he ordered! Its got about 25 hours on it, so I know he isnt going to repower!
So, my question is:

Does anyone else have this set up?

If so, what is the optimum prop size?

The boat does have a Dole Fin, genaeral use has Mom and Dad sight seeing on the river, but, it would be nice to get them on plane a little quicker.

Thanks!

fishgutz posted 04-20-2008 11:04 AM ET (US)     Profile for fishgutz  Send Email to fishgutz     
Here is a start. This boat specs out very similarly to your Dauntless 14. http://www.yamaha-motor.com/assets/products/otb/bulletins/ bulletin_4stroke_highthrust_al_edg-145cc-t50tlr.pdf
What gear ratio does the motor have? Is it a Bigfoot or standard gearcase? If it is a Bigfoot a 12 or 13 pitch prop should work well. If it is a standard gearcase then maybe a 10 or 11 inch pitch.

I'll crunch some numbers and get back to you later.

dghinseaford posted 04-20-2008 11:13 AM ET (US)     Profile for dghinseaford  Send Email to dghinseaford     
its a standard, merc 50 4 stroke. thanks alot! i look forward to your # crunching! dgh
Tom W Clark posted 04-20-2008 11:19 AM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
I recommend the Mercury Trophy Sport four blade propeller in the 10-5/8" x 13" size.
fishgutz posted 04-20-2008 04:36 PM ET (US)     Profile for fishgutz  Send Email to fishgutz     
Every number I tried and using comparisons from Mercury's, Tohatsu's, Suzuki's, Honda's and Yamaha's websites say 10,11 or 12 inch pitch prop. I really don't think you can turn a 13 inch pitch prop and get that boat up on plane in a reasonable amount of time.
I've found you will have to use trial and error to really decide. I have a Dauntless 14 with a 75 Mercury 2 stroke motor. I have 3 props. A 17 inch pitch Black Max, an 18 inch pitch Mercury Vengeance SS prop and a 19 inch pitch Black Max prop. Performance is very similar with each. The 18 Vengeance works best.

I would go with an 11 inch pitch SS prop.

dghinseaford posted 04-20-2008 06:14 PM ET (US)     Profile for dghinseaford  Send Email to dghinseaford     
Thanks guys, so what size X 11" pitch should I try first?
fishgutz posted 04-20-2008 06:35 PM ET (US)     Profile for fishgutz  Send Email to fishgutz     
You choices are limited. The diameter will be 10 1/2 inches give or take an eighth to a quarter of an inch either way.
Tom W Clark posted 04-20-2008 07:28 PM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
You might be surprised. Long time forum member Dick had a 1999 Mercury 50 HP four stroke on his 1999 Montauk and used the 13" Trophy Plus to replace the three blade he had. That boat was able to achieve in excess of 32 MPH.

The Dauntless 14 is about the same weight and beam as the classic Montauk, though considerably shorter. I would expect similar performance.

There is also a 10-5/8" x 12" Trophy Plus available.

Regardless of what prop is chosen, you do NOT chose it based on diameter. You first choose a line of propellers to try, and then determine what pitch in that line is best suited for the boat. The diameters are determined by the propeller's designers.

Not all lines of propellers will turn the same RPM vis-a-vis a given pitch.

dghinseaford posted 04-20-2008 07:48 PM ET (US)     Profile for dghinseaford  Send Email to dghinseaford     
there is a sticker on the lower unit, above the cavitation plate which says 1.83:1 12x22
is this an indicator?
Tom W Clark posted 04-20-2008 08:13 PM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
1.83:1 is the gear ratio of the lower unit.

12x22 is the actual tooth count of the gears. 22 / 12 = 1.83

Tom W Clark posted 04-20-2008 08:16 PM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
Correction: I meant to write Trophy Sport above, not Trophy Plus (an entirely different propeller, not applicable to this motor.)

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