02 semi stagger Lightning 700hp 575 SCi's
Went from -1 IMCO SC's to -4SCX's(blueprinted lowers, #6 shafts, 17" 5bl 35P props) and didn't lose any speed
Went from limping home on a broken upper every 100 hours or so to a few months of hard shifting(both drives) and metal on the drain plug(one drive) at 180 hours.

Took drives apart
Metal came from lower gear severely pitted-one drive
Hard shifting came from galled cone and cup-both drives. This was hard on the shift forks
New cones are lighter and don't fit the clutch shaft-needed new shafts
Propshaft seal surfaces were severely seal grooved-had them flamesprayed with ceramic
Drive pinion thread stretched when torqued to spec with brand new Snap on torque wrench-new inputs
1 upper drive gear had a few small pits

Parts list X 2!
all bearings and seals
flamesprayed propshafts
drive and driven lower gears
drive and driven upper gears
forks
cones
clutch shafts
input shafts
1 U joint each drive

History
Installed drives
Changed oil at break in time, 5 hours?
Both started leaking out input
Sent both inputs to IMCO and they replaced the seals for free(except shipping to them)
They continued to leak but only about a cup a season so I left them alone
Changed oil every 25 hours or more often if at end of season. Always pulled drives at end of season.
One time I noticed the drive guide screw was coming loose and gouged gimbal ring. Mentally irritating, functionally fine.
280 hour 700hp 575SCi's w/stock couplers and computers(rev limited at 5350rpm). One coupler has 480 hours.
Maintained well, driven hard but not stupid.
Very disappointed in the lifespan. The time and cost spent rebuilding these(along with the original installation) maybe should have been spent on Arnesons????
Gotta wonder!

Have a friend with same boat. 750+ HP and more RPM, Broke a lower, paid IMCO to fix it. Broke both lowers a year later. He's dealing with them right now. He's probably at 100 hours total time.

Dick Tryce/ Mr. Gadgets/ Dicks Performance Marine has hooked me up for drives and parts for years. He's great!
Thanks again Dick

Good Luck
Rob

If I am understanding correctly, you went from breaking an upper every 100hrs to needing to rebuild every 180?

The disappointment you have is understandable, I am just not ready for all that goes with the Arneson. I decided on the SCX uppers, and to sell my XR uppers before I actually break them again to offset some cost. Even if I need to rebuild the IMCOs every 150, thats something I can plan for and live with. Disintegrating the XR randomly anywhere between 0-80 hours over and over makes the boat a whole lot less fun.

Needing to rebuild every 180 hours is TBD at this point.
Maybe it was dumb luck that the lower started going away. The other side looked fine. I will say that the vert shaft lower bearing height was not what was spec'd on IMCOs spec sheet. Bearings shouldn't have changed it. I shouldn't have had to adjust it.
Maybe the lighter cones will help keep them from galling.
Maybe they'll last longer this time around, I can only hope.
Unlike the SC's, I always felt confident in them and they never left me idling back to the dock for 2 hours!
Any time I started to get overconfident in them I'd remember the old, stock couplers and calm down. lol

I could have saved one lower gear set and all the upper gears(polished cups and they looked decent, needed new brass rings though) except for the one drive gear with pits.
Forks could have been cleaned up.
The clutch shafts could have been turned down .004 to work
The bearings could all have been reused.
But, when flirting with disaster I did all I could to prevent it.
I have a lot of decent used SCX parts for sale.

lower drive gear


upper drive gear

Sure thing, I was careful not to say "problems". All that goes with it, for me, in my current situation.

Here's the short of it: Due to several factors I haven't gotten to do more than 6 drive bys in 14 months. Over the course of those 14 months I've replaced everything power-train with new except the uppers themselves and just got it all back together a few weeks ago. I replaced, repaired, changed, and added a bunch of other stuff while it was apart. It was a labor of love and I'm just done messing with it for a while and want to drive this thing I've been pouring money into for over a year to remind me why I bought it. A few hours after the crate arrives from IMCO I'll be back in action. Same selection of props I've amassed, I won't be dealing with a completely different handling boat, and I finally won't be spending another summer dialing something in (hopefully) or undoing what was a real unexpected pain to get done the first go round. Has nothing to do with a problem I have with Arneson. I think it is extremely cool and if it truly added 10mph to my boat in addition to all the other advantages it provides over what I have currently that would be impressive for sure.

Had I known that AFTER I replaced the transom assemblies it would toast an engine, and then to discover the why and have to address that, and knowing now what a huge undertaking this ended up being, I might have planned differently. Unfortunately the end result of luck and my choices has me looking at a boat that I've replaced all but the uppers, and its fairly hard to say anything besides "fine" replace those too. Cost is a factor, and I'm pretty sure the Arneson kit x2 would cost more than the SCX upper and helmet x2. I thought I was at least making a respectable choice not taking another go with the XR's or anything based on it and choosing the SCX.

The Arnesons do/will/would give you roughly a 10 mph increase in both your midrange and top speed. This is the norm and there is no reason that your boat would be any different.

Setup isn't that difficult, certainly not a summer season worth of testing.

Handling will not be hugely different, it would dock better with the Arnesons and it would track and steer better with the Arnesons. These are facts from boat owners that have run the Arnesons/converted to Arnesons from the Bravo style drives. Rough water handling will also be improved over the Bravo style drives.

Propellers will not be the same as you noted on a boat your size (guessing it's a 38' Donzi) so that is a VERY valid concern.

Not to mention the extra cost, length it would add affecting my slip/lift and eliminating the ability to easily use the swim platform and ladder. And the fact that I would need to undo things I just finished putting together.

But if you're saying putting the Arneson setup on my boat will be as easy as swapping the XR's for the SCX's, and the total cost would be the same or within 5%, and the labor would be the same or within 5%, and I'll be back on the water 7 days from now, and you have someone lined up to pay me new price on all the 4 hour old stuff I just installed that will be unneeded with an Arneson conversion. and you'll buy it all back if its not as easy and as speed beneficial as you say... Plus I'm fairly sure I'd be the very first 38zx with Arnesons, which cool in itself, I'd rather not be the trailblazer with my own $40k+ on the line. So if you aren't willing to buy everything back and comp my labor if the end result does not end up being a 95-100mph, 14,000lb, 2003 38zx non-daytona I'm not really willing to chance it, and we should just leave it as that.

Look, I understand your product is great, so are others too, but I do not want all that goes with an Arneson conversion, for me, right now. Its a hassle for me, and you're not likely to convince me otherwise. Not your fault that 14 months ago when all I thought I would end up doing was a gimbal pin and an oil change I got caught up and already committed to a bravo style outdrive long before I fully considered all my options. Such is life, and my choices right now are limited to other uppers I can swap in place of the XR, so that I can enjoy this boat for a change.

Your right

Alright. I'm actually not trying to be rude here. I just didn't expect to have to defend or explain myself to a vendor in a thread specifically about another competing vendor.

I explained my personal motivations for not choosing the Arneson at this time, but I'm open to it. So if you would do me the courtesy of explaining to me the difference between installing the Arneson Bravo conversion on a new install vs an existing one. To quote your page on the conversion: "The #7M Kit is ideal for new installations where by you want a reliable high performance outdrive on your new boat. Installation takes just a few short hours and requires the use of a drill, and a few hand tools." This infers (and I believe I personally comprehend the reasons why after some research) installing during a new build up is ideal, but on an existing installation of a Bravo outdrive, there is more to it than a few hand tools, a drill, and a few short hours. Please correct me if I'm wrong, and I stress that I mean that sincerely and not in the condescending way. If I am incorrect about your product I would like to be educated.

With that, I am also left wondering, why choose the "Bravo Conversion" at all? What is being converted on a new boat that is being assembled for the first time and has not had anything on it to that point? I'm sure there's some simple explanation to this along the lines of the "Bravo Conversion" essentially meaning "Universal" and less involved than most Arneson setups in some way.