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Author Topic:   MONTAUK 170: Re-power with Yamaha 100-HP

dirk posted 12-24-2006 05:53 PM ET (US)
I have the intention to repower my 2005 Boston Whaler Montauk 170 with a Yamaha 100-HP EFI four-stroke. What prop do I need?
jimh posted 12-24-2006 10:25 PM ET (US)
What is the gear ratio of your engine? What is the maximum rated RPM for your engine? What is the top speed you anticipate with your usual weight and load?
You can look up the information specific to your motor in the owner's manual or from the manufacturer's literature.
You can add up the weights of the boat, motor, crew, and gear to arrive at a total boat weight. Or just weight the boat on a scale.
Once you have the boat weight and horsepower, you can estimate the maximum boat speed using Crouch's Calculator.
Once you have a target boat speed, you can use the Propeller Calculator to estimate the propeller pitch.

Crouch's Calculator
http://continuouswave.com/cgi-bin/crouchcalc.pl
Propeller Calculator
http://continuouswave.com/cgi-bin/propcalc.pl
This information will help us predict the propeller pitch.
Or, if you don't want to bother with all of that calculation, put on a 19-inch pitch three blade and give it a try.
The Judge posted 12-25-2006 11:05 AM ET (US)
Did Yamaha come out with the 100 again? Last I looked they stopped/changed to 90 in 2003 or so and they were all carb'd.
Lil Whaler Lover posted 12-25-2006 12:54 PM ET (US)
In other parts of the world, such as Australia, Yamaha never chanbged the 100 and 80 horsepower 4-strokes to 90 and 75 horsepower designations. I would assume this also applies to Europe.
Teak Oil posted 12-25-2006 08:32 PM ET (US)
I would use the same prop that 170 owners have on their boats equipped with Mercury 90 four stroke engines. The Yamaha 100 doesn't really make 100hp, hence the change in hp designation in the States.
There should be lots of threads here on prop selection for the 170's in the "Post-Classic" forum
imko posted 12-26-2006 12:05 PM ET (US)
Dirk,
The dealer in holland told me that next year the Montauk 170 will have a 100 hp Mercury.
http://www.marinepower.com/news/single/5263D18047D4426FC125711C003086B3
I think the Laser II 13¼ x 20" is the perfect prop!
Regards,
Imko

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Author	Topic: MONTAUK 170: Re-power with Yamaha 100-HP
dirk	posted 12-24-2006 05:53 PM ET (US) I have the intention to repower my 2005 Boston Whaler Montauk 170 with a Yamaha 100-HP EFI four-stroke. What prop do I need?
jimh	posted 12-24-2006 10:25 PM ET (US) What is the gear ratio of your engine? What is the maximum rated RPM for your engine? What is the top speed you anticipate with your usual weight and load? You can look up the information specific to your motor in the owner's manual or from the manufacturer's literature. You can add up the weights of the boat, motor, crew, and gear to arrive at a total boat weight. Or just weight the boat on a scale. Once you have the boat weight and horsepower, you can estimate the maximum boat speed using Crouch's Calculator. Once you have a target boat speed, you can use the Propeller Calculator to estimate the propeller pitch. Crouch's Calculator http://continuouswave.com/cgi-bin/crouchcalc.pl Propeller Calculator http://continuouswave.com/cgi-bin/propcalc.pl This information will help us predict the propeller pitch. Or, if you don't want to bother with all of that calculation, put on a 19-inch pitch three blade and give it a try.
The Judge	posted 12-25-2006 11:05 AM ET (US) Did Yamaha come out with the 100 again? Last I looked they stopped/changed to 90 in 2003 or so and they were all carb'd.
Lil Whaler Lover	posted 12-25-2006 12:54 PM ET (US) In other parts of the world, such as Australia, Yamaha never chanbged the 100 and 80 horsepower 4-strokes to 90 and 75 horsepower designations. I would assume this also applies to Europe.
Teak Oil	posted 12-25-2006 08:32 PM ET (US) I would use the same prop that 170 owners have on their boats equipped with Mercury 90 four stroke engines. The Yamaha 100 doesn't really make 100hp, hence the change in hp designation in the States. There should be lots of threads here on prop selection for the 170's in the "Post-Classic" forum
imko	posted 12-26-2006 12:05 PM ET (US) Dirk, The dealer in holland told me that next year the Montauk 170 will have a 100 hp Mercury. http://www.marinepower.com/news/single/5263D18047D4426FC125711C003086B3 I think the Laser II 13¼ x 20" is the perfect prop! Regards, Imko