bor

iTrader: (1)

I m looking for some advise /thoughts on the propshaft height on a twin engine 30 ft cat whit bravo its sportmaster drives

I have both standard and -2" lowers available for them and was thinking to start high at 3.5 - 4" above running surface and space down if it is to high.
Did a few search here but couldn t find much

thx

bor

4mulafastech

I don't have experience with I/O, but my twin outboard Talon 22 with 6" jack plates liked the prop shaft centerline 2" above the running surface. This was turning 14.5" diameter Mazco cleavers. 3.5-4" seems a little high, unless the props are further from the transom compared to outboards.

bor

iTrader: (1)

Thx 4mula tech !

whit the i/o the props are a bit further from the transom and the set back is 7" on the ITS , but wouldn t be very far compared to your set up .
I was thinking to try to get the bullets out of the water or far as possible to reduce the drag .
I looked at ton s of pics but its hard to see so thats why I look for some input on here cat owners or that have experience whit them .

glassdave

iTrader: (1)

make sure you have bullet proof lowers i believe running them as a surface drive is very hard on them.


Sorry i lost track of your email and PM been super busy good luck with the project.

timmoore

I've got mine 1 1/2 inches above the bottom on my 24 Skater with Bravo 1s, I think I could have gone a little higher. I'm using 14 3/4 inch props.
Mine has the notches in the transom so it's like they are on 12" setbacks. I think 2 - 2.5 would be great with some bigger diameter props.
Just my 2 cts...

timmoore

Running them surfaced is hard on them.
I've broken 2 small propshafts on mine and that is with very little HP.
Upgrading to 1 1/4s this winter, I hope they stay in 1 piece

4mulafastech

Yes, definitely hard on lower units. I also lost a propshaft on a Merc 2.5 after about 230 hours and a little N2O.

bor

iTrader: (1)

Hey Dave !

No problem glad youre so busy ! just looking to get much info as possible and probily start at the high end and do some R&D to get some data on what it does at different heights ,Arnaldo contacted formal owners but they wouldn t help whit measurements and experience of there I/O so we are on are own .

as I have the luxery I plan to start high whit the shorty s and then go down also gonna put the engines on a driveshaft to get cg better .

gonna keep u posted !!

bor

iTrader: (1)

hi Tim ,I love your project ! Mine also have quite a big notch and the set back of the ITS so could be a little higher but yours running great whit the power you have ! I have the 1 1?4 shaft s so that s a bit better also heared it can throw blades when running a high X .

But you only can space down not up that s why I want to strart high and have the option to go down if it not work .