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More Prop Talk ...... by MarkS » Sat Dec 15, 2012 5:48 am
Subject boat = 1971 GT150 - 1978 Evinrude 115 V4 w/PT&T - Mission is to get WOT at 55-5600, with max SAFE speed.
Starting point/baseline - 1st Prop - OMC brand 12 3/4 X 21P ALUM - WOT 5400 @ 54MPH - Note: gets a little hairy over 53mph, nature of the hull design as I am told.
2nd Prop - OMC SST 12 3/4 X 21P Stainless (teflon coated) - *WOT 5200 @ 52MPH - Note: more left on the table in the speed, *chine walk gets too severe to continue. Porpoising at lower speeds if trimmed above 1/4. Probably going to be the fastest/best all around, if the set-up can be refined to control the boat at top speed.
3rd Prop - OMC Raker 13 3/4 X 22P Stainless - WOT 5100 @ 50MPH - Note: Too much pitch & bow lift, didn't like much if any trim, porpoise and chine walk prevalent, much better suited to CVX style hulls with pad.
4th Prop - OMC SST II 13 3/4 X 19P - *WOT 5800 (pulled back, was still winding up!) at 48MPH - Note: not enough pitch, might be a good prop for heavy loads or pulling barges.
5th Prop - Power Tech PT03(?) 13 1/5 X 19 w/custom cupping and pitch added - WOT 5200 @ 48MPH - Note: Stern lift created by this prop gives a whole new "feel" to the boat, thought we had it here. RPM and MPH just not where they need to be.
Back to props 1 and 2, with a Solas Amita 3 13 X 19P as a back-up/spare/emergency. Will probably try raising the motor up another hole as suggested, and maybe add a Bob's True Tracker to help with stability. All numbers posted from recollection, so please forgive me if they're not exactly as stated earlier.
Special thanks to David P. (CGOAMN), & Tim at Performance Props Inc - Soddy Daisy, TN.