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Author Topic:   Prop Sizing for Nauset at High Elevation

milehiwhaler posted 09-27-2006 06:33 PM ET (US)
I would like some suggestions on prop sizing for my "new to me" boat.
Specs:
1973 Nauset
12 gallons of fuel
1985 90 HP Evinrude (Two Stroke Obviously)
CMC Trim/Tilt System
Operating Elevation 6000 feet
Use: Cruising
Occupant weight: Two people at 175 pounds each (250) total
One Battery
Furniture: RPS and Fiberglass Center Console
Gear: 75 Pounds
Any suggestions would be appreciated! Thank you in advance.
Tom W Clark posted 09-27-2006 11:30 PM ET (US)
6000 feet?! That 90 HP Evinrude is only going to put out 65 or 70 HP at that altitude and only be abe to turn a 15" pitch prop.
The Judge posted 09-28-2006 10:36 AM ET (US)
Can't really tell from your info but Tom is probably right with pitch.
What prop are you running and how many RPMS at WOT?
skookum point posted 10-02-2006 02:41 PM ET (US)
My experience with several different boat/motor combinations is that you'll need to drop 4" of pitch when going from sea-level to 6000 ft.
Tom W Clark posted 10-03-2006 09:14 AM ET (US)
Based on John's comment, you will need either a 15" or maybe even a 13" pitch prop.
MitchD posted 10-03-2006 11:01 PM ET (US)
I have run boats all over Colorado lakes since 1982, including a 1972 16' Mark Twain tri-hull with a 1984 90hp Evinrude. A 19 pitch prop worked perfectly fine with WOT of 35+ mph. I also had a 20' EbbTide with a 285hp IO, and ran a 19 pitch at a scary 50+ WOT. I currently have a 2005 190 Nantucket with a 135hp Merc, also a 19 pitch. It runs WOT at 40+ mph on the plains lakes and 35+ on the mountain lakes.
I am not a prop expert by any means, but I understand that the lower pitch sacrifices speed for power. I do have a hard time getting the Nantucket on plane quickly, and seem to lose plane at around 25 mph, which is my preferred cruising speed. I have to cruise at 25+ or at displacement speed of less than 20 mph.
E-mail me for a ride-along on Chatfield. October is the best month for cruising and fishing, as the water skiers and jet boaters are off the lakes.
milehiwhaler posted 12-03-2006 05:59 AM ET (US)
Sorry for taking a while to make a reply post. Thanks for everyone's advice. I now have in my possesion an 11, 13 and 15 pitch propeller I will try them all when I take the wraps off in the spring and let you know the outcome.

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Author	Topic: Prop Sizing for Nauset at High Elevation
milehiwhaler	posted 09-27-2006 06:33 PM ET (US) I would like some suggestions on prop sizing for my "new to me" boat. Specs: 1973 Nauset 12 gallons of fuel 1985 90 HP Evinrude (Two Stroke Obviously) CMC Trim/Tilt System Operating Elevation 6000 feet Use: Cruising Occupant weight: Two people at 175 pounds each (250) total One Battery Furniture: RPS and Fiberglass Center Console Gear: 75 Pounds Any suggestions would be appreciated! Thank you in advance.
Tom W Clark	posted 09-27-2006 11:30 PM ET (US) 6000 feet?! That 90 HP Evinrude is only going to put out 65 or 70 HP at that altitude and only be abe to turn a 15" pitch prop.
The Judge	posted 09-28-2006 10:36 AM ET (US) Can't really tell from your info but Tom is probably right with pitch. What prop are you running and how many RPMS at WOT?
skookum point	posted 10-02-2006 02:41 PM ET (US) My experience with several different boat/motor combinations is that you'll need to drop 4" of pitch when going from sea-level to 6000 ft.
Tom W Clark	posted 10-03-2006 09:14 AM ET (US) Based on John's comment, you will need either a 15" or maybe even a 13" pitch prop.
MitchD	posted 10-03-2006 11:01 PM ET (US) I have run boats all over Colorado lakes since 1982, including a 1972 16' Mark Twain tri-hull with a 1984 90hp Evinrude. A 19 pitch prop worked perfectly fine with WOT of 35+ mph. I also had a 20' EbbTide with a 285hp IO, and ran a 19 pitch at a scary 50+ WOT. I currently have a 2005 190 Nantucket with a 135hp Merc, also a 19 pitch. It runs WOT at 40+ mph on the plains lakes and 35+ on the mountain lakes. I am not a prop expert by any means, but I understand that the lower pitch sacrifices speed for power. I do have a hard time getting the Nantucket on plane quickly, and seem to lose plane at around 25 mph, which is my preferred cruising speed. I have to cruise at 25+ or at displacement speed of less than 20 mph. E-mail me for a ride-along on Chatfield. October is the best month for cruising and fishing, as the water skiers and jet boaters are off the lakes.
milehiwhaler	posted 12-03-2006 05:59 AM ET (US) Sorry for taking a while to make a reply post. Thanks for everyone's advice. I now have in my possesion an 11, 13 and 15 pitch propeller I will try them all when I take the wraps off in the spring and let you know the outcome.