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Author Topic:   Prop size for 70 HP '85 Evinrude VRO

sodden_skier posted 08-26-2007 10:59 AM ET (US)
Hello,
I'm looking for some advice for the optimal prop size for a 1985 Evinrude 70 HP VRO. It's for a 17' classic Montauk-like, but somewhat obscure Whaler, so we can just consider it a Montauk.
I'm not exactly sure what's on there now, but am hoping to increase RPMs and top speed.
Any recommendations are appreciated.
Thanks!
sodden_skier posted 08-26-2007 11:11 AM ET (US)
If anyone is interested, the model is a Whaler Bass Boat, so it has casting decks in the front and back...which adds considerable weight.
Tom W Clark posted 08-26-2007 11:26 AM ET (US)
The Bass Boat model, offered from 1971 to 1976, is not a Montauk and should be referred to as a Bass Boat model. These are somewhat rare but many are still n existence providing lots of fun to their owners.
http://continuouswave.com/whaler/cetacea/cetaceaPage05.html
The Bass Boat was the heaviest of all the 16'-7" models, at least 50 pounds heavier than a Montauk.
Most 16'-7" Whalers with the classic OMC 70 HP used a 17" pitch propeller. I would think an OMC/BRP SST )or Viper) 13-1/2" x 17" propeller would serve you well as would a Stiletto Advantage I in the 13-/14" x 15" size.
If you do a lot of waterskiing, a drop in pitch may help you achieve greater pulling power.
To really identify what propeller might be best, you will need to figure out what prop you have now, your maximum RPM and your top speed measured with a GPS.
sodden_skier posted 08-26-2007 12:02 PM ET (US)
Thanks for the recommendations, Tom. I don't use this boat for waterskiing at all. I am only interested in top speed performance.
Tom W Clark posted 08-26-2007 12:19 PM ET (US)
If top speed is your goal, then you want the 13-1/4" x15" Stiletto Advantage I, part # 21315
Tohsgib posted 08-27-2007 11:17 AM ET (US)
max RPM on a 1985 is 5500. Max speed or WOT on a 23 year old engine might not be good for it.

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Author	Topic: Prop size for 70 HP '85 Evinrude VRO
sodden_skier	posted 08-26-2007 10:59 AM ET (US) Hello, I'm looking for some advice for the optimal prop size for a 1985 Evinrude 70 HP VRO. It's for a 17' classic Montauk-like, but somewhat obscure Whaler, so we can just consider it a Montauk. I'm not exactly sure what's on there now, but am hoping to increase RPMs and top speed. Any recommendations are appreciated. Thanks!
sodden_skier	posted 08-26-2007 11:11 AM ET (US) If anyone is interested, the model is a Whaler Bass Boat, so it has casting decks in the front and back...which adds considerable weight.
Tom W Clark	posted 08-26-2007 11:26 AM ET (US) The Bass Boat model, offered from 1971 to 1976, is not a Montauk and should be referred to as a Bass Boat model. These are somewhat rare but many are still n existence providing lots of fun to their owners. http://continuouswave.com/whaler/cetacea/cetaceaPage05.html The Bass Boat was the heaviest of all the 16'-7" models, at least 50 pounds heavier than a Montauk. Most 16'-7" Whalers with the classic OMC 70 HP used a 17" pitch propeller. I would think an OMC/BRP SST )or Viper) 13-1/2" x 17" propeller would serve you well as would a Stiletto Advantage I in the 13-/14" x 15" size. If you do a lot of waterskiing, a drop in pitch may help you achieve greater pulling power. To really identify what propeller might be best, you will need to figure out what prop you have now, your maximum RPM and your top speed measured with a GPS.
sodden_skier	posted 08-26-2007 12:02 PM ET (US) Thanks for the recommendations, Tom. I don't use this boat for waterskiing at all. I am only interested in top speed performance.
Tom W Clark	posted 08-26-2007 12:19 PM ET (US) If top speed is your goal, then you want the 13-1/4" x15" Stiletto Advantage I, part # 21315
Tohsgib	posted 08-27-2007 11:17 AM ET (US) max RPM on a 1985 is 5500. Max speed or WOT on a 23 year old engine might not be good for it.