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Re: Shorter drives?

My boat is a 23' WPM cat with a NA solid roller 598 home built and not dynoed. With a standard length Bravo it ran best with a 30 Bravo at 6100 RPM through 1.36 gears. My x is pretty high and I really didn't think the shorty would help. Luckily I have a buddy that let me try his before I bought mine. With the shorty I turn the 30 6300 RPM and can swing a 32 6000. The slip is essentially the same in all scenarios. Don't you have a 28 Daytona? I have a friend with a 28 and he runs 2" above the sponson on a box. Without a box you will need to be about even with the bottom of the sponson. My propshaft is even to 1" above the sponsons. Obviously mine is a single. Good luck testing!

Craig

Re: Shorter drives?

Quote:

Originally Posted by WETTE VETTE

Yes, I have a 28 TD Daytona with 496 ho stockers. When parallel with bottom, my propshafts sit about 1/2 to 1" above the very bottom tip of the sponsons. I have all ready ordered two IMCO satin shorties, so I hope all goes well.

Re: Shorter drives?

Quote:

Originally Posted by gsmith9898

Do you want to sell the one?

No, I'm looking for another one.

Re: Shorter drives?

Quote:

Originally Posted by BenPerfected

Payton,
I run a non-stepped V with twins and my prop shafts (when parallel) with the bottom are .75" below the bottom. I get on plane a little slow with Bravo 1's in a 30' hull @ 8,000 lbs. (dry).
I started at 4.25" below (including a 3" spacer) w/27P Mirage props at Lake X. Base line was 97 MPH w/ Imco 2" shorties. Switched to Bravo 1's (same effective pitch; 27p Mirage to 28p Bravo 1). At this point we started reducing the spacers...2", to 1" and then to no spacer. The only significant change was the speed increased each time we raised the drives 1". We ended at 103MPH+. After a re-rig, the following year I tested at .75" below the bottom vs. the final 1.25" from the previous year. No change in speed. In my straight V, 1" below is close to optimum.
Sprague

Well, here I had decided I didn't need to try them. After reading this, maybe I do need to give it a try.
I've got a 32' running surface, 25 degree V and I would guess about an 18" notch. I run labbed, 25" mirage+s. A friend has a set of labbed 26" Hydros I could probubly get for about what I could sell my Mirages for.
Maybe I need to start thinking about this again.

Setup on a lower unit is pretty simple, right? Just torque the verticle nut and set preload on the carrier nut? And get everything in the right place. :eek:

Re: Shorter drives?

Every application is going to be different - TESTING - is the only for sure way to know - I know on my application (35 Fountain single step) the RPM increased by 200 - up 2" & up 2" prop pitch netted me 5 MPH

Re: Shorter drives?

Here's a few pictures at eye level with propshaft and bottom of boat. Does it look like I'd be safe going up 2"?

Re: Shorter drives?

Quote:

Originally Posted by BenPerfected

I run a non-stepped V with twins and my prop shafts (when parallel) with the bottom are .75" below the bottom. I get on plane a little slow with Bravo 1's in a 30' hull @ 8,000 lbs. (dry). We ended at 103MPH+. Sprague

Sprague,

1) Does your boat have a notch in the transom?

2) Did you notice any increase in speed at your cruising range....let's say 3500-4000rpm?

Thanks

Re: Shorter drives?

Payton,
Gear lash has to be set up.. Pinion height and driven gear depth.. The Imco lowers are different than Merc cases. Well the number of shims are different to get the same pinion ht..

Dick

Re: Shorter drives?

Dick, how much to make the swap for me? If I simply bring you my lowers?

How much more if I watch? :D :D

Re: Shorter drives?

I just ordered my pair of Shorties, so we'll just see !! :drink: