Rank: Newbie
Groups: Member
Joined: 7/28/2010
Posts: 1
Points: 3
Location: North Alabama
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Heres the scoop-
Boat 223 Cobalt Condurre 1989 20* deadrise, weighs about 3600 lbs full.
Motor: 454 mercruiser 330 hp with bravo drive-not the mag, cast internals
Current Prop: 23p mirage from 1989, not a plus
Current top speed 55mph
Current top RPM 4700 to 4800: about 200 revs too much for this non mag motor.
Drive ratio is 1.5:1
The mirage carries the bow nicely and perfroms great. But according to prop slip calks I am at 19% slip.
Are the mirage plus props of today better than mirage of 1989. I am guessing I need to go up an inch in pitch, and my rpms will settle around 4500 top end, and 4600 or more once I finish exhaust work.
According to slip calc at 10% slip I should be close to low 60's. Is 10% slip unreasonable?
LC
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Rank: Administration
Groups: Member
Joined: 2/27/2007
Posts: 1,789
Points: 5,080
Location: Sarasota
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Hey LC
I saw your post on THT before I saw it here on our forum ha ha.
I think running a new Mirage Plus or Quicksilver Thunderbolt will hold the rpm down where you need it, and cut down on that slip%.
Its been said that the Mirage Plus has a little more cup then the original Mirage. I've never ran them back to back though so I can't really back that up with any data.
They don't make a 24 Mirage, so its either the 23 or the 25.
I'd try the 23 first. If it hooks up and cuts that slip down to 10% or so, you'll see a gain in speed.
As I mentioned on the PM, if the new 23 doesn't hook up, we can go with a Tempest plus for some better bite, or cup the Mirage a little more.
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