I'd like to get another 1-2 MPH out of my boat. It's an '88 Baja Sunsport 196 with a 500HP SBC and an Alpha SS with 1.50 gear ratio. I did a little back to back testing last weekend with my two props. With 2 people and 3/4 tank of fuel, it ran...

- Quicksilver Mirage 23P (not a plus - totally stock)
GPS 78.1 MPH @ 5800 RPM
7% slip!

- Custom Spinelli 26P 3-blade (similar to Hydromotive)
GPS 78.2 MPH @ 6000 RPM.
20% slip

5800-6000 RPM is a good spot for this motor. I also periodically run nitrous which adds another 500 RPM and definitely want to remain below 6500 RPM. Can the Mirage or Spinelli be reworked to gain some speed or would another prop design be better?

Lab Finishing your Mirage will add a couple hundred rpm. If there is speed to gained, this should bring it out.

By the way Pl um Crazy is one of my favorite Mopar colors...........

Plum Crazy,

If your numbers are accurate I would say don't touch that Mirage. It is not going to get any better than 7% with your boat. This is actually extremely low for a 3B propeller. The Spinelli obviously is not the ticket for your boat. the round ear blades will perform better on your hull.

Julie

Labbing the prop will not improve the slip #'s. In fact they will more than likely go up a %. But if you want 1-2 more mph, what are you willing to sacrifice? Losing a little in the mid will give you 200rpm on the top and more than likely your 1-2 mph.

It is funny how we all talk about slip #'s as if they are MPH. The Spinelli is slipping 20%, but running slightly faster than the 7% Mirage. On my boat I personally want the fastest prop regardless the slip %. The way different mfg's rate their pitch #'s it is all pretty much BS anyway. As for Plum Crazy I personally think a labbed 25 Mirage or a 3 blade Hydro may be worth looking into. Plum Crazy is my dad's old boat and we were unable to find a faster prop than the "26" Spinelli, and we tested a lot. Our experience was the Spinelli lost more MPH / additional passenger than the Mirage or Hydro's. The Spinelli had less blade area which allowed the WOT RPM, and the high slip. Get rid of weight and the speeds increase. We never really messed around with propping for 5500 ish RPM and that may be worth exploring. Plus while on the NOS the RPM increase may be more starting from 5500 than at 6000. How are you doing Dan?

Craig

Agreed, slip may go up, but in some cases the rpm out weighs it!

Wette, I really prefer the Mirage all around. The Spinelli is more difficult to steer while idling and slips too much in corners. I actually tried a Mirage Plus 25p once. I ran about 76 @ 5200 RPM. Maybe I should try propping to around 5500 RPM. I think a standard Mirage 25p would get me there.

A labbed 25 sounds like it could be the ticket.