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Author Topic:   ALERT 15, 90-HP Yamaha

edwardschnog posted 10-13-2008 11:54 AM ET (US)
I was told by a technician that my ALERT 15 [later described as having a Yamaha 90-HP two-cycle motor] will perform better with the POWERTECH NRS-3R-18P-YM90 prop (including PORT-516 vent holes) than it would with the 19-pitch standard Yamaha black stainless propeller. What is better: Choosing a lower pitch and a more aggressive cupping, while balancing for the same engine RPM? Or vice versa? What is the effect of both extremes?

Tom W Clark posted 10-13-2008 02:02 PM ET (US)
Edward,
The PowerTech NRS series is a three blade propeller with high rake. It is going to be very similar to the Stiletto Advantage, the Turbo 1 and the Mercury Laser II.
The nominal drop to 18 inches of pitch is reasonable. Try it and see.
The one caveat about the PowrTech prop is I do not think they have yet gone to a square bore hub (Mercury Flo-Torq) as most other manufacturers have so if you buy it and it done not work out it will more difficult to sell as it will be hubbed for a Yamaha.
Any square bore prop will have near universal applications across brands.
edwardschnog posted 10-13-2008 06:17 PM ET (US)
Dear Tom,
Thanks for the tips...
Do you know the exact difference between the PTR and the NRS props? Both are bow lifters right? I was told that the PTR has more aggressive cupping, so I would need to go with a lower picth when buying the PTR prop. Please explain the differences and why someone should choose the one over the other.
My 15ft Whaler Alert model is equpped with a 90HP, 2 stroke Yamaha.
At WOT the engine hits 5200rpms. Engine is equipped with the standard black stainless prop. Top speed is 62mph (GPS clocked)
elaelap posted 10-13-2008 07:35 PM ET (US)
62 miles per hour! Yikes. I "only" get slightly over 41 mph wide open on flat water out of my classic 15 with a Yamaha 60 four stroke, 15 inch pitch aluminum prop. Hey...I ain't complaining, and I won't be spending very much time at that speed anyway, thank you very much.
Tony
edwardschnog posted 10-13-2008 08:23 PM ET (US)
Sorry, correction.....
Not 62, but 42 MPH !!
jimh posted 10-14-2008 11:47 PM ET (US)
Propellers that run at elevated mounting height usually benefit from added cup.
jimh posted 10-14-2008 11:57 PM ET (US)
[Thread closed--there are three concurrent discussions on this same boat and motor. Post follow ups to http://continuouswave.com/ubb/Forum4/HTML/006387.html --jimh.]

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Author	Topic: ALERT 15, 90-HP Yamaha
edwardschnog	posted 10-13-2008 11:54 AM ET (US) I was told by a technician that my ALERT 15 [later described as having a Yamaha 90-HP two-cycle motor] will perform better with the POWERTECH NRS-3R-18P-YM90 prop (including PORT-516 vent holes) than it would with the 19-pitch standard Yamaha black stainless propeller. What is better: Choosing a lower pitch and a more aggressive cupping, while balancing for the same engine RPM? Or vice versa? What is the effect of both extremes?
Tom W Clark	posted 10-13-2008 02:02 PM ET (US) Edward, The PowerTech NRS series is a three blade propeller with high rake. It is going to be very similar to the Stiletto Advantage, the Turbo 1 and the Mercury Laser II. The nominal drop to 18 inches of pitch is reasonable. Try it and see. The one caveat about the PowrTech prop is I do not think they have yet gone to a square bore hub (Mercury Flo-Torq) as most other manufacturers have so if you buy it and it done not work out it will more difficult to sell as it will be hubbed for a Yamaha. Any square bore prop will have near universal applications across brands.
edwardschnog	posted 10-13-2008 06:17 PM ET (US) Dear Tom, Thanks for the tips... Do you know the exact difference between the PTR and the NRS props? Both are bow lifters right? I was told that the PTR has more aggressive cupping, so I would need to go with a lower picth when buying the PTR prop. Please explain the differences and why someone should choose the one over the other. My 15ft Whaler Alert model is equpped with a 90HP, 2 stroke Yamaha. At WOT the engine hits 5200rpms. Engine is equipped with the standard black stainless prop. Top speed is 62mph (GPS clocked)
elaelap	posted 10-13-2008 07:35 PM ET (US) 62 miles per hour! Yikes. I "only" get slightly over 41 mph wide open on flat water out of my classic 15 with a Yamaha 60 four stroke, 15 inch pitch aluminum prop. Hey...I ain't complaining, and I won't be spending very much time at that speed anyway, thank you very much. Tony
edwardschnog	posted 10-13-2008 08:23 PM ET (US) Sorry, correction..... Not 62, but 42 MPH !!
jimh	posted 10-14-2008 11:47 PM ET (US) Propellers that run at elevated mounting height usually benefit from added cup.
jimh	posted 10-14-2008 11:57 PM ET (US) [Thread closed--there are three concurrent discussions on this same boat and motor. Post follow ups to http://continuouswave.com/ubb/Forum4/HTML/006387.html --jimh.]