x-dim
 

What is the shortist housing made for bravo 1, I need to shorten up the x-dim by 3 1/2 to 4". Or what will k-planes do for top speed with a drive that is to low? If I cut out a new hole for the drive then the exhaust will dump on the swim platform.

IMCO have lower units up to 3" shorter than stock.

http://www.imcomarine.com/pages/sterndrives.html

you can use a 3" offset extension box, but you would have toraise the engine and relocate your exhaust. And you'de be dumpin onto the platform

imco 3" shorty

raise it where you want it, then get custom tailpipes made.

How do you know that that you have to raise it that much?????

3.5- 4 inches is a LOT.

I would try the shortened lowers first for sure. Mine was high and just lowering it just one inch made a huge difference.

Griff, I was told the x-dim for my hull should be approx. 3" below the pad, mine is 7". It's an old 1985 aero, I was told its the same hull as the 24' pantara, they like to set the x-dim low for ride quility not performance, which is histerical because it's a performance boat.

I would try the 3" lower first. My 28 Pantera with a notched transom was set with the propshaft 3 1/4 - 3 1/2 inches below the bottom. It was a little high and and I couldn't carry the bow enough. I lowered it 1". Cruise speed went up 3-4 mph @ 3600rpms. Slip went down, and I gained 1-2 mph on the top end. Easier to getting on plane and could trim it higher without blowout to carry the bow better.

I just talked to imco, he said I sould try a 3" shortie, the kit comes with all componets. He said I'd have to cut off the cavatation plate and install a new "shield" thats what he called it, so that the prop would clear, anybody done that? Also he said I could expect about a 4 mile an hour increase, but I was told by a boat builder that I could expect a 10 mph increase? What gives?

An increase of 4 mph is certainly possible. 10 mph would be miraculous. Keep us posted

at best is 2 mph per inch, so three inch shorter drive you might get 6 max, but count on 4 are 4.5 mph increase

What's the thought on k planes or trim tabs?. I know I'd be able to have better control, but what about speed increase? is it a bandaid cure for the wrong x-dim?

Trim tabs will not help to gain speed. They will only slow you down when they are in the down position. Yes they will help keep the nose down in the rough.

I HAVE A BRAVO WITH PERFORMANCE 1.36 GEARS AND AN IMCO 2 INCH SHORT LOWER YOU CAN HAVE FOR $2000 .USE THE LOWER AND KEEP THE UPPER AS A SPAIR.THE 1.36 OR 1.50 GEAR CHANGE IS IN THE UPPER IN THIS DRIVE.ADD ANOTHER $1000 AND GET THE EXT BOX WITH WING PLATES FOR STEERING.ALL FOR 3K

That's what I'm using 1:36, but I'll still be at the very least 1" to deep. Do you have the trim extentions for that box?

Try a blackhawk drive. It is short enough to get you where you want to be.

Who manufactures blackhawk drives? Where is the web site? Thanks

Blackhawk is made by Merc

Blackhawk -no longer made by Mercury

Blackhawk, good drive?

Blackhawk is a duo prop surface drive made by Mercury for a few years, I think 1995-98.It will fit the Bravo bellhousing,and what I have heard worked best on cats.

there is a brand new blackhawk drive on ebay, search # 2466095435, also contact xs marine ,they were cutting down bravos, email [email protected] ask for allan

I don't know what kind of boat you have,
but I would think twice before I bought a Black hawk.

If your boat is a V-hull 21-28'
I would go whith mcollinstn (post#4).

When you cut the transom, mine is 2 peices, 1" thick plywood glued by fiberglass in between and on the front and back with gellcoat on the outside. do you cut out a larger square on the inside 1" slabe say like 1 1/2 by 1 1/2 foot, then a smaller 1' by 1' on the outside slab? then glue those together and fiberglass up and regellcoat the outside? Or how is this done ?:eureka: :confused:

I would stay away from the black hawk drive just because of the availability of parts, Props , and people that are familiar with them.

what about surface drives like a Kamma or a arrneson??

There is someone who makes a surface drive that will adapt to a bravo housing.

ttt