Beefing up a Bravo 1
 

putting around 530 - 550 hp in my cat . 468 NON BLOWER.

what can I do to beef up the drive and also what precautions can be taken to help. thank you !

if you bring it up EASY to get and plane and dont launch it you shouldnt have to much trouble with the drive you have...

not an expert,but a billet top cap would be my first choice...i did it on mine

Use the search function in the upper right corner. There are several threads discussing this dilemma. It's been beaten like a dead horse

thanks going to try it .

How you beef up a B1??? That's easy. Sell it and buy an ASD#7M.

first question is what year bravo and what model bravo do you have. there are some differences between years like vertical shaft diameter and the difference between models is quite a difference like the bravo x upper gears are not straight cut gears like the xr also the cases are not the same the x has aluminum chimmnies which snap off if the thing ever got launched and re-enteres without throttling back and the xr has steel chimmnies. all the gears in a xr are forged and the x has cast. the lower on a xr is pretty obvius by looking at the propshaft diameter. the shaft on a xr is all steel and one piece and the x has a stainless 2 piece fusion welded shaft which always twists and breaks at the weld. the xr also has a billet aluminum propshaft bearing carrier. you can change the vertical shafts to a better hardened shaft from imco or teague. also other things to know is the newer style sleeker upper case drives are all shimmable uppers as opposed to the older models where predetermined shimming. difference is they say as per mercruiser school i just went to was the newer ones will shift and should have better gear wear.

It seems you never break the items you can easily replace but typically do break the items that you can't replace easily....or at least I seem the break the items I don't have spares for. Therefore, keep an entire spare drive laying around. If your luck is like mine something else will break but the drive won't! :)

Have 2 bravo spares and a blackhawk.. I just hate getting towed home after you buzz up the river turning heads..LOL

Thanks for all the responses.. Is there a reputable guy to send it out to if I want to have work performed. I wont mess with bravo's .

1990 B1 should have sn starting with OL or OF or earlier. That would be the thin floored helical cut gears. They are forged, but then machined for the helical gears. That old of a case is thinner in some spots than the newer ones. They used to set them up pretty loose back then. But the most common problem was pushing the floor out of the fwd driven gear. New B1X uses thick floored gears and steel tower in the case. Also uses the XR vertical shaft, but still has the 1" propshaft. The newer the case the stronger they casted them. A 2004 case will have more meat in it, so adding a steel tower and good top cap with a steel tower is a common upgrade that lives in a lot of cases. There are several guys in my area with that setup with much more power than you have. It must be driven with respect, but most have decent luck with that setup.

What rpm are you running at WOT? The higher the rpm, the easier on the drive, to a point. Less blades on the prop is too. No 5 or 6 blades unless you like maintenance.

Hope that helps.

Dick

While I agree Mr. Gadgets upgrades are worthy, I feel if you have a newer bravo it's easier to simply buy an XR upper and use your regular bravo lower on it. XR gears can handle more "instant" power/torque but will wear themselves to death over time. Helical cut regular bravo gears will last much longer but can't handle the torque big HP brings with it. It's kind of like flipping a coin where you loose heads or tails and win only if the coin lands sitting on it's edge.

well its the 1990 bravo upper, with an xr lower, with low water pickup. [ i know xr lower means no extra longevitey due to the most crucial parts in the upper.]

I am running a 26 4 blade 6000 now, going up to a 28 4 blade and most likely will run up to 6700.

have a ton of money in this motor, just getting it freshend up now and going to dyno it before it goes in in March.

whats the billet cap that they talk about ?

again, thanks for the help

billet cap is available from a couple of reputable businesses:
max machine worx...teague...and probly others...while the cap wont make the upper part bulletproof,it does strenghten it in the weakest area...good luck

You need a rev limiter....and at least one spare drive. :) It helps that your in a fairly light weight boat.

Mr. Gadgets is always dead-on with his advice.

The reason I recommend the helical gears is because of the poor track record the XR upper gears are having these days. My theory is, if you dont have enough power to knock the teeth off the helicals, stay with them. A Procharged 950 hp 24' Checkmate is running the helicals without problems. Others in the 800-850 range are also. I agree, if you can find a good set of XR upper gears, they are stronger, but if they last 10hrs, well not such a good deal. They used to last 250hrs on a regular basis, not now. I have a set (XR) I pulled out of my personal drive with 300 on the driven gears and about 270 on the pinion gear that show no signs of pitting.. They were made around 2002.. Ran approximately 700hp through it.
I would rather see someone buy a B1 X upper.. add an XR ribbed top cap (well built comes with bearings and relatively cheap) with a stud kit, and you have a good drive. 550hp is not that much power these days..

Dick

Ditto, and this plan is working perfectly for me for the last 2yrs of hard running 650hp ish a side.

I run around 800 thru my b1 and for the price of the drives they do ok. One thing I wouldnt do is run an xr lower. Bigger bullet that causes more drag with no increase in longevity.
I have a b1x laying around that I will try out. Reading what mr gadgets is saying very informative. His posts usually are.

Poker,
It is ok to run the XR lower. The lower cases on the B1 and XR lower are the same size. The only difference is the propshaft, bearing carrier and lower gears (driven gear has a larger hole in it to fit the tapered splines on the XR propshaft).
There was a short bullet on the 88 drives, but since they made it longer, the dimensions have stayed pretty much the same.
Hope that helps.
Dick

Imco Sc
 

I have been running IMCO SCs on my boat for 64 hours now. I have 900HP aside and i have not had a problem yet. I turn them to 6000RPM every time i go out. 1.36 ratio 36 pitch props. My season is over now and would like to have someone tear my drives apart and see what should be replaced. When i emptied the drive oil there was alot of shavings. I live in Windsor Canada and was looking for someone within a couple hours drive. Any drive experts near me.THANKS

So the bullets are the same size or maybe I should say shape?
I destroyed an xr as easily as a bravo1. For me it's just easier to have a couple extra b1's laying around then fix the xr. I can get b1 in good shape for 800 to a grand. That's two for the price of an xr rebuild. I use an imco shorty now so the lower question was more for the orig poster having one on his b1. I have seen some guys think they are helping their drives.

You need to talk to MR. GADGETS. He knows the drives very well. And also is very reasonable.

Drive Identification
 

So the only difference between the B1 X and the XZ is the lower prop shafts size? Is there a way to identify the X or XZ drive vs. a regular B1 or an XR? Serial number? Is there a better / stronger case to shop for and can this be identified externally or by serial number?
Thanks.

Shortly after i saw metal like you my vert shaft broke. AND, when Mr. gadgets tore them down both upper and lower gears were about to go. The SC's looks awesome, but are bearly better then a XR.

Mr. Gadgets is a GREAT guy and I trust all his advice. He does good work on drives also.

But 900hp will break any bravo based drive, and if they don't break they will wear out much faster.

OP, Mr. Gadgets can set your drive up to last though. Especially if you run his oil, bravo shop oil, something better then the mercury oil!

Inspector,
The XZ had the old style input shaft ujoints (with grease fittings). So that is one other difference between the newer B1X. The XZ serial would start with OM.. Not sure when the B1X came out, so it could start with OM, but OW would not be an XZ. OW's are hump backs.
If you have a drive with 1" propshaft, and it uses the XR upper case (retainer nut on the input shaft has holes instead of tabs), then it is a good bet it is a B1X. Same XR upper case with old style large unjoints (grease fitting) and 1.25" propshaft, could be an XZ or XR. You would have to pull the back or top cap to look at the teeth on the gears.
There are some that can look up the serial number and give more details, I dont have that info.
Best way to determine what you have is to open it up and inspect it. Decal sets usually head you in the right direction, but they can be misleading is some cases.
A stronger upper case, well in my opinion the B1 is stronger because the input snout is thicker where the retainer nut threads are. But you have to add a steel tower to the case to finish that statement. The newer the cases are (mid 2000's) the more meat they seem to have. So if you are shopping there a lot of things to look at. I have seen one XR upper case that the tower pulled the threads out of the case (all I saw was the case, not sure what caused it). Merc towers thread down 1" into the case. When a tooth snaps off the XR upper gears, it can push the pinion out the front of the case and in most cases the snout is cracked right at the thin spot on the threads. So nothing is bullet proof. They all have weak spots. And that is what the chase is all about, fixing the weal spots.
Hope this info helps.
Dick