Cutting a Bravo lower
 

A couple of weeks ago I posted a thread about cutting down a Bravo lower by two inches. Well we cut it today! Everything went well, thanks to Marvin Chivers and the equipment at L&W Machine. I will index the two halves and weld them together next week.

The progress continues.

The two sections are now apart and the final cut is taken. All of the settings have been saved on mill's computer. :)

Hiya Maxx! Dang------you're really gettin' into that stuff aren't ya? Looks very interesting---keep posting as the project unfolds please. :)

Hey Mark, how-ya been? I have been rebuilding and upgrading drives and have seen a couple of shortened lowers. I fell out of my chair when I heard what the price was to shorten one! Therefore, I thought I could offer a lower cost / quality alternative to folks who want a shorter drive but were apprehensive about spending big bucks on buying a Shortie or having one shortened. :)

Are you going to cut and weld the cavitation plate or make a new one out of stainless?
Just wondering,
Thanks,
Caleb

Timewarp, I am going to cut the lower cavitation plate and weld on a new piece to the upper. Kind of reversing the two.

Maxx, are you going to cut and respline the vertical shaft like the rear axle jobs you've referred to or use an imco 2" shorter unit? I've been involved in the axle jobs before and agree it should work. I have replaced my alpha with a bravo and now I've heard that the bravo is 2" longer than the alpha! I'm kinda pissed because I feel like I'm losing "free Speed" if there is such a thing. 2" shorter at 90 mph has got to make a difference since the alpha used to be there and ran fine at 70 and turned and planed ok. Keep me posted, this is cool. Greg

Greg, I did the same thing (switched from an Alpha to a Bravo) I measured both drives from the input shaft to the prop shaft and they had the same dimensions. However, the physical size of the Bravo is much larger and the overall dimension is a bit longer thus they produce more drag. This very reason is why my boat manufacturer moves the X dim up 2 inches for Bravo applications. As far as the vertical shaft goes, we can't cut and respline because the lower section of the shaft is case hardened and we would still be in that area even after taking off 2". I am going to cut the shaft in the large diameter area, stub one side, drill the other and press the two pieces together. Then weld with a stainless alloy. This should be plenty strong 'cause welding with the stainless will not crystalize the metal at the weld joint. The upper splines would twist off before the weld joint would break. I am communicating with an aftermarket, drag racing, drive train company to produce a vertical shaft at a reasonable price.

i would be interested in hearing how the project goes i might be on the customer list soon for a shorter lower myself.

WOW what a project!!!! Keep the pictures coming :D:D

Jon

Maxx, so in essence the skeg is 2 inches longer? An Imco shaft is about $300 Do you think you can do it cheaper? How did you decide where to cut the drive at? Cool. Greg

I will continue to post as we progress. Greg, we measured down the vertical shaft journal to 1/2" below the bottom race seat and made our cut there. I didn't want to get too low, because I need to be able to fit a tig torch inside to weld and seal that area. Also, the Bravo has an oil passage that leads from just below the lower race area to the lower Torrington bearing. I still need to perform one more machining process to keep that functional. As far as the shaft goes, the jury is still out. I am trying to have them produced at a reasonable price. Being a former drag racer, I could purchase a pair of aftermarket axles for around $300.00 and a Powerglide input shaft for around $200.00. I don't see where there is anything super special, compared to those items, about a Bravo vertical shaft that warrants the price these companies charge for them. If you or anyone would like to discuss it further; I can be reached via email: [email protected] or phone: 757-739-5196.

Very interesting project Maxx/John---keep the pictures coming and keep alearnin' about them drives son! :D

Mark, will do! Audiofin, your project looks intense as well. I am very fond of Formulas and can't wait to see the finished product. :)

I know John personally and he really knows his stuff when it comes to these kind of projects. He helped me rebuild my bravo to withstand the 650PSHP blower motor I built and so far so good The next step is to run the new lower and hopefully make some good gains. I must say that this was a well thought out process and should work really well. I also have to agree with him that the vertical shaft should be ok when welded, (I have a background in metallurgy), but like he mentioned he also sent my vertical shaft off to a company to have it evaluated at a more competitive price. I must say it looks good so far.
DT

Price
 

Thanks for those nice comments Don. Now that my head swelling has gone down, I have received a lot of emails requesting a price to do this job. At the risk of sounding too much like an advertisment, and getting kicked off the board; I figured I can do the entire job for well under a $1000.00. That would include cutting the drive and the shaft, re-shimming, re-sealing with new propshaft seals and O rings, and re-setting the rolling torques. The drive would be returned ready to bolt on, just a little shorter. Options will include after-market shafts, new bearings /races, and nose cones. I don't want to get too specific out of respect for the OSO rules, but I would be glad to email the prices. I plan to include a pretty good garauntee on the vertical shaft, also.

Maxx you project is very interesting. I believe the prices for most marine stuff is way too high just because it says marine. A few years ago I rebuilt a TRS gimbal the merc prices for the bearings and seals were very expensive. I noticed they all had Timkin and Chicago Rawhide numbers and could be bought from a good auto parts store for literally a fraction of the price. I think they all cost me around 15 bucks instead of around 100. E mail me more info on your shortening as I was planning on it this winter and would be intrested in your service.

B.R.S. did you get my email I sent you? There has been a bit of a delay in welding the two pieces together. I sustained a flash burn this week, but I picked up some eye drops from my doctor so everything is feeling better. Hopefully, I can get to it this weekend. Man, with all the injuries I've had recently I feel like Tim Allen :rolleyes: BTW, you may have noticed that I have not mentioned the "M" word; I am afraid that if I do I will have an irresistible urge to double prices.:p

Maxx hows the project going? Hows the eyes? I've had eye burn myself and it feels like sand in the eyes. Hope you feel better. Greg

Greg, my eyes are starting to feel better; thanks for asking. I need to wait a few more days before getting back to it, and I think I will toss my self darkening hood! So, for right now everything is in limbo. As soon as I can get back to it I will post some pics.

MAXX, please mail me a price to upgrade my Bravo HPs into XR/XZ equals plus your shortening operations.
thanks
Shawn

John it looks like I will have time to nock off early on Fri if you want to come up. If you are call before you leave for OH so I can schedule accordingly.

B.R.S. and shawn, I sent emails to you guys. Shawn, I need to get up with Chris at Stern Drive Specialties on current prices for gear sets etc. ( I buy all of my Merc stuff from sterndrivespec)

Maxx thanks for the compliments. I hope to go to paint tomarrow.

Jon

updates???:confused:

mxz800, I posted a couple of pics illustrating the indexing of the two sections. However, I just got the shaft today and checked for shimming, straightness, backlash, etc. Everything worked out great, and I am very encouraged. I will complete the welding and cosmetic touches next week and post some photos. I have kept a journal of the entire process; logging info about any glitches and ideas that would make everything come together a little smoother.

John/Maxx, I think I am going to need my drives shortened by two inches as well. It would be nice if you could cast a nose cone right into the drive---kinda like IMCO does. I still might be interested anyway.

Q. I wonder if it is more critical to have better hydrodynamics i.e. a nose cone when the drive is deepe into the water or higher up near the surface/surface piercing? Can anyone answer that?

By the way, I have XR drives from the year 2000

Mark / Kaama, I was wondering the same thing. Precision Manufacturing in Fl makes a nose cone / LWP that is not as large as some of the others I've seen. I was going to do some testing with that one to see if it makes any difference. Give me a call when you get a chance :)

John how did the trip to Fla go?

B.R.S. I'll bee heading out Friday. Hopefully things will turn out well.

outstanding project

How do you determine what x-dim. you sould have?

aero-offshore, check out this post. Folks in this thread explain it a lot better than I could. Basically, if you have to trim your drive way up to get the speed out it or you are using a prop with a lower pitch than other boats equipped similarly to yours, you may be a little low in the water.

Http://www.offshoreonly.com/forum/sh...ht=X+dimension

Thanks Maxx, but now i just blew a vane in my brain.! Spark from Sparky Marine says 2.750 to 3.00 for my hull a 24' ,24 degree dead rise v botom is about right, I was just lookng for more thoughts. by the way that was measuring from the bottom of the v to the prp shaft center line at an even trim.

Have you measured yours?

Some folks have expressed an interest in this thread, agian. So, I brought it back out.

So Maxx are you offering this service? Hows the prototype holding up? What kind of $$ are we talking about?

Yes Dyno, we will be offering this service. Our website with prices will be up soon and we will have a banner-link on OSO. You can give me a call, also, at 757-971-2704.

Cool Maxx you the man!!! I'm going to do some testing myself before I decied to cut them. I'm going to need an add on steering set up this winter( if I stay employed)
Thanks
Don