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  Prop for 1977 Outrage21

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Author Topic:   Prop for 1977 Outrage21
kohrfam posted 09-30-2014 01:51 PM ET (US)   Profile for kohrfam   Send Email to kohrfam  
I'm looking for a prop for my 1977 21 outrage with a Honda 150. The motor is on a Bobs 8'' setback hydraulic jack plate.
Any suggestions on where to start? Thanks.
jimh posted 10-03-2014 09:41 AM ET (US)     Profile for jimh  Send Email to jimh     
I suggest the following method as a way to start the determination of a propeller for use with a boat:

--determine the anticipated maximum speed to be obtained, based on the engine power, the boat weight, and the hull design

--use the anticipated maximum speed as a target speed in calculating the propeller pitch

--select an initial propeller of the calculated pitch, and test the performance

--evaluate the performance.

Method for initial performance evaluation:

--compare the engine speed at maximum throttle with the manufacturer's recommended full throttle engine speed range; the maximum engine speed obtained in testing should be in the upper part of the suggested range;

--if the engine speed at maximum throttle is too high compared to the suggested range, change the propeller pitch to a higher pitch;

--if the engine speed at maximum throttle is too low compared to the suggested range, change the propeller pitch to a lower pitch

Once a propeller pitch has been found that puts the engine speed at maximum throttle into the upper part of the recommended range, further evaluation can be made.

To assist in this selection, you can employ two on-line calculators I have created and published. To calculate an estimate of maximum speed based on power, weight, and hull design, using a method suggested by George Crouch and implemented in an on-line tool by me, see

Crouch's Speed Calculator
http://continuouswave.com/cgi-bin/crouchcalc.pl

To calculate propeller pitch based on engine speed, gear ratio, propeller pitch, propeller slip, and boat speed, see

Propeller Calculator
http://continuouswave.com/cgi-bin/propcalc.pl

jimh posted 10-03-2014 09:46 AM ET (US)     Profile for jimh  Send Email to jimh     
Do you have any performance data from any testing you have done with your 1977 Boston Whaler OUTRAGE 21 and HONDA 150-HP outboard engine mounted on an 8-inch set back bracket that you can provide here? Having some data for a starting point will be very helpful in selecting a propeller.
Tom W Clark posted 10-03-2014 11:36 PM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
I recommend a 14-1/4" x 19" HONDA Turbo 1, Stiletto Advantage or TURBO Turbo1 (they are all the same propeller)

Top speed should approach 48 MPH if the jackplate is adjusted to its fullest potential at speed.

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