Thread subject: Whaler Central - Boston Whaler Boat Information and Photos :: seeking propeller advice
Posted by dbcollen on 07/13/12 - 11:41 AM
#1
I have a 1974 outrage 21 with twin 4 cyl 115 mercs ser# OC2XXXXX. I presently have Solas Amita 13x21 props, they seem to be the correct pitch. at WOT lightly loaded I can overrev the engines slightly (5400 rpm) with my normal load the engines stay at 5000-5200 rpm WOT. The engines are supposed to run 4750-5250 rpm. I am wanting to replace the aluminum props with stainless. The pair of mercury 13.?x19 ss props that I have let the engines run up to 5700 rpm.
Posted by Tom W Clark on 07/13/12 - 1:00 PM
#2
I offer the same advice I gave back in April:
I recommend a pair of 13-1/4" x 19" Stiletto Advantage 4.25s (or the Turbo 1 equivalent) with DE-501 hub kits or Flo-Torq hub kits of your choice.
The motors should be raised three holes up, maybe even four holes up.
How fast of the boat going at 5400 RPM?
Posted by dbcollen on 07/13/12 - 1:18 PM
#3
the motor is 2 holes up, and getting some ventilation in the seas I run in, the boat was going around 46 smph.
Posted by Tom W Clark on 07/13/12 - 1:29 PM
#4
Two holes up now? That means the bolts are going through the third (middle) holes in the motor mounting brackets?
o <-- All the Way Down
o <-- One Hole Up
o <-- Two Holes Up
o <-- Three Holes Up
o <-- Four Holes Up
The props are ventilating because they are cheap aluminum props. The Advantages will not ventilate like that.
5400 RPM with 21" pitch prop at 46 MPH is about 11 percent calculated propeller slip. That's a lot but not surprising for aluminum props with little cupping
The Stiletto Advantages will yield calculated slip close to zero or even negative.
With the 19" Advantages and the motors raised one or two more holes, I predict the combination of better propellers and less gearcase drag will improve your boat speed by 2-4 MPH and you will see WOT engine speed of about 5200 RPM.
Edited by Tom W Clark on 07/13/12 - 6:46 PM
Posted by dbcollen on 07/13/12 - 8:10 PM
#5
I just got back from fishing, and I looked at the engines, I have them 3 holes up right now, only one hole left below the bolts. I am not questioning your wisdom, just trying to learn. Why would the stiletto 19 props run 5200 when the quicksilver 19 stainless props I took off run 5700 rpm?
Edited by dbcollen on 07/13/12 - 8:13 PM
Posted by Tom W Clark on 07/13/12 - 8:25 PM
#6
Nominal pitch is the same but the blade geometry is completely different.
Posted by dbcollen on 07/13/12 - 9:48 PM
#7
What is the difference between the turbo1 and the advantage? What is your opinion of turning point express props?
Edited by dbcollen on 07/13/12 - 9:50 PM
Posted by Tom W Clark on 07/14/12 - 7:03 AM
#8
The Stiletto Advantage, Turbo 1 and Yamaha Performance Series 3-Blade are all the same propeller, different labels, different prices.
All three are made in Indianapolis, Indiana by Precision Propeller Industries, Inc (PPI) which is now owned my Yamaha. PPI has been manufacturing propellers for decades and made most of Yamaha's props for many years and Yamaha liked them so much they bought the company from its founder in 2008.
I do not think much of Turning Point propellers though I have no personal experience with the Express.