jgordon525
Recruit
- Joined
- Apr 1, 2010
- Messages
- 1
Hey all,
I am just finishing up repower of my old Wellcraft Nova 250XL from single OMC800 stringer to VP260A w/280PT drives (clamshell covering the actuators). Need to choose the first trial prop and since I have all the data needed to make the calculations I figured it might be an interesting challenge for all you experts out there. Really informative for the rest of us!
The boat:
79 Nova 25xl 25' and change 9.5' beam
Most of the Nova's had 2 260hp mercs / alpha/MR drives and would run 55-60 WOT. The dual engine boat weight 5200 lbs. Mine is the single engine version with a taller freeboard. Lets say 4200 lbs(?).
Previous power
260HP rebuilt SBC
OMC 800 Stringer driver w 1.41 ratio
15 x 15 OMC prop
lost track of how deep the drive was set
WOT 4200 / 33 MPH (with no hesitation getting there)
3500rpm cruise / 26 MPH
Repowered
VP 260A SBC From donor boat. Compression and leak down are great.
VP 280PT 1.61 ratio
280 will swing a 16" diameter
I set up the drive depth so the cavitation plate +1/2" from the hull.
If I am making the same power...... what do you think a good prop is to start with?
Typical usage 4 adults and gear. 120 gallons fuel. Used offshore in Southern California. Hoping we can improve the cruise speed right out of the gate.
Will going to a 16" dia prop help? Since the OMC 800 stringer had no problem getting to WOT, I am guessing I could have pushed a 15 x 17". Now with the VP and 1.61 ratio can I get away with going to 17" pitch and the 16" diameter? How do you calculate slip?
Of course I am expecting to fine tune from the first prop. But since I have a lot of info to work with (enough?) I am betting one of you guys might be able to get REAL close on the first shot. Will keep everyone posted on the results.
Thanks for your input!
Joel
HB, CA
I am just finishing up repower of my old Wellcraft Nova 250XL from single OMC800 stringer to VP260A w/280PT drives (clamshell covering the actuators). Need to choose the first trial prop and since I have all the data needed to make the calculations I figured it might be an interesting challenge for all you experts out there. Really informative for the rest of us!
The boat:
79 Nova 25xl 25' and change 9.5' beam
Most of the Nova's had 2 260hp mercs / alpha/MR drives and would run 55-60 WOT. The dual engine boat weight 5200 lbs. Mine is the single engine version with a taller freeboard. Lets say 4200 lbs(?).
Previous power
260HP rebuilt SBC
OMC 800 Stringer driver w 1.41 ratio
15 x 15 OMC prop
lost track of how deep the drive was set
WOT 4200 / 33 MPH (with no hesitation getting there)
3500rpm cruise / 26 MPH
Repowered
VP 260A SBC From donor boat. Compression and leak down are great.
VP 280PT 1.61 ratio
280 will swing a 16" diameter
I set up the drive depth so the cavitation plate +1/2" from the hull.
If I am making the same power...... what do you think a good prop is to start with?
Typical usage 4 adults and gear. 120 gallons fuel. Used offshore in Southern California. Hoping we can improve the cruise speed right out of the gate.
Will going to a 16" dia prop help? Since the OMC 800 stringer had no problem getting to WOT, I am guessing I could have pushed a 15 x 17". Now with the VP and 1.61 ratio can I get away with going to 17" pitch and the 16" diameter? How do you calculate slip?
Of course I am expecting to fine tune from the first prop. But since I have a lot of info to work with (enough?) I am betting one of you guys might be able to get REAL close on the first shot. Will keep everyone posted on the results.
Thanks for your input!
Joel
HB, CA