spectras only

This picture of my Gaffrig GPS speedo [about 73mph] was taken before re-pitch to 26P .
Most pitch/speed calculation are approximate but here it is >

Boat weight - 6000lbs
running surface length at max speed 10'
approx SAE HP at the crankshaft 680-690HP total , twins
WOT -5150 rpm
drive ratio - 1.65
speed length ratio-5.21
max speed to date-74.64 mph
calculated slip- 0.08%
pitch ratio-1.68

Boat runs pretty efficient for a 24* deadrise pad hull

4mulafastech

Spectras - I've always loved your Mirage! Very unique and has to be one of the smallest twin IO boat around. Looks like you got her dialed in nice. Would be fun running you with my 292. Should be really close. Although I would like it to be a little rough out to give me a little advantage!

pqjack

according to brett,a 26p bravo is closer to 25p...you could have your props re-pitched to a real 26,or even 26.5p...might be just what you need....

spectras only

pqjack, Brett is right as usual. My B1 26 props checked out to 25P , one blade was even less at 24 checking with pitch gauge.

4mulafastech, my props are thinned as well to get WOT @ 5000 with 26P . The 350 mag with 300 shaft HP wouldn't turn a 26 to 5000rpmm even with 1.65 dr ratio. My boat would run faster with the 27 Mirage Plus three blade but I prefer the four blade for midrange acceleration. You'd have a slight advantage with the extra length in the rough, albeit my boat takes on rough with the K Planes trimmed, only my kidneys may object ,haha. The Mirage has a high freeboard that helps.
here's a picture of some conditions we go through Porlier Pass towards Vancouver Island.


http://www.youtube.com/watch?v=z8IVujFhCHU

Porlier Pass with nicer weather

http://www.youtube.com/watch?v=kdZHLqsiKSw

looseconnection

So 25" is what a 26bravo checks at I would say I would be good with a full 26" or stock with a bit more cupping. That would drop me 150 to 200 rpm so it would put me down in the rated wot range or 4800 to 5000

Spectra did you cut down your diffuser ring?

Thanks for the help

spectras only

I'm sure cutting the diffuser back 5/8 would help gaining a few mph but it might hamper getting on plane times! I'd love to try some different props to experiment but we have no prop exchange programs in my area and shipping props back and forth with Brett is not in my plan. Local buddy who did some exchanges with Brett are happy though. He likes 5 blade Maximus props [ $$$ ] but those are usually better suited to BB power. Our SB boats are best suited to B1 and Mirage Plus props to run with. You might try to cut the diffuser off and let me know how it worked out before I do it with mine,haha.