20' Cigarette - Shorty Advice Needed
 

Hello all!
Wondering if there's anyone in the know who might provide advice regarding a shorty for my 20' Cigarette (1986).
Currently have supercharged 454 w 5lbs boost running through a Bravo 1. X dimension is lowish (not sure exact measurement). Spins 27' Mirage to about 5000 rpm delivering low to mid-70's speed. Looking to up the ante a little this year with headers and potentially a -2 shorty+prop. Any thoughts on gains, driveability, etc.
Many thanks!

There is usually a bit of trial & error involved. For rough estimating you usually dont want to be deeper than about 5" or higher than 3" in reference to the propshaft to bottom of the boat. At least for starting puroses. That said depending on what you are trying to accomplish going further either way may be required. ;) Jamie

Thanks for the tip Jamie... I'm going to try to get something to get me into the range and see how it goes.
Best regards,
Yoryi

No problem .. :) J

You should be able to get more speed than that with your set up.

This might help. My buddys '79 22 donzi with same exact drivetrain and boost runs 82 on GPS with 28 Bravo 1 prop. Bottom design is the same and weight is close enough to same.

Trim drive level with bottom of boat, and put a level on the bottom going out to the drive - where does the line of the bottom of the boat hit the drive in relation to the water intake - right in the middle, near the top, 1" from bottom, etc???? This is quickest way to tell you where your x dimension is compared to his.

Another buddy changed his 20 to a bravo without a supercharger, and is running same speed as you are.

Hang Time,
My propshaft is currently around 7 and 3/4" or 7 and 7/8" below the bottom of the boat. Before the s/c it ran 66.6 on radar and last week it ran 76.2 on GPS both times with the Mirage 27 (maybe the Bravo prop is faster?), and with the s/c as the only mechanical difference (many years apart). FYI, we believe this 454 to be a strong (maybe not) running 330 and not a 365. Any suggestions or info with respect to the two boats mentioned would welcome.
Thanks,
Yoryi