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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.
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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 |
Originally Posted by 199025sxtWarlock
(Post 3569847)
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 |
Mr. Gadgets is always dead-on with his advice.
Originally Posted by Mr Gadgets
(Post 3569816)
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 |
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 |
Originally Posted by Mr Gadgets
(Post 3570025)
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 |
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
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