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-   -   upper or lower ? (https://www.offshoreonly.com/forums/drives-lower-units/220948-upper-lower.html)

blue thunder 12-07-2009 11:26 AM

I'm putting about 700hp through standard bravos at 5400rpm. The weak link seems to be the top cap. Both of recent my upper failures were WOT in very rough water. One rotating with pressure on the top cap in forward, wiped out the gears. The other with forward pressure on the lower gear, over zealous throttling caused feedback to the gearset and popped it out of gear then WOT back into gear, broke the top cap.

I have also twisted off propshafts in big water. If you are not in big water or you can control yourself better than I, your bravos will live fine with a billet top cap and a good shower. Upgrading the propshafts to 1-1/4 would be wise as well and not all that expensive.

Griff 12-07-2009 03:56 PM

If I were you, I would just put nose cones on the drives that you have and run them. They won't last forever, but should survive a few seasons with good throttling habits.

rssteiny 12-07-2009 04:08 PM

95% of my running is on a pure flat river and a lake the same, i do 1 poker run where depended on weather conditions can get 3,4 footers, i also baby it onto plane never over 3000 rpms and I ease it to wot, i dont just slam the sticks down. i have good drive showers so you think a billet cap and bigger shafts and nose cones and let her go. my hp may not be quite 650 any how but it will be at least 620 and the boat is not that heavy.

Thanks Rick

blue thunder 12-07-2009 04:41 PM

I run nose cones on standard bravos. I do poker runs and usually run pretty hard. I run in the upper eighties to low ninties and the nose cones seem to help. I would feel pretty good about my drives if I had the bigger propshafts and better caps. I'll probably work on that next season. The only reason I would pop for the imco lowers would be if I wanted to raise the propshafts 2". But I am already up 2". How about you, could you gain some speed raising the props?

rssteiny 12-07-2009 07:03 PM

my 32 active thunder has a high x now so i think i need to stay standard length, maybe i should just put nose cones on my bravos and billet caps and let it at that. i was running 87 mph at like 18% slip and in my rev limiters, this year i should be another 50 hp or so and proped right with the nose cones pulling down my slip numbers and i hope to see mid 90s.

Griff 12-07-2009 10:04 PM


Originally Posted by rssteiny (Post 3002273)
95% of my running is on a pure flat river and a lake the same, i do 1 poker run where depended on weather conditions can get 3,4 footers, i also baby it onto plane never over 3000 rpms and I ease it to wot, i dont just slam the sticks down. i have good drive showers so you think a billet cap and bigger shafts and nose cones and let her go. my hp may not be quite 650 any how but it will be at least 620 and the boat is not that heavy.

Thanks Rick

I really don't think you'll have any major issues with regular Bravos with the type of boating you do. Stronger top caps couldn't hurt, but I really don't think you'd need them. What you may think about is looking for a deal on a spare drive, just in case. Not because I think you'll need one, but because if something is going to break, it will do so at the worst time and when you can't find a good price on another one.

t500hps 12-07-2009 10:09 PM

I also was thinking nose cones on your lowers and start shopping for a spare would be a good idea......ever notice you never need the things your prepared to replace??? Those stronger top caps aren't that expensive and not a bad investment either.

Mr Gadgets 12-08-2009 08:54 PM

rssteiny,
I have two customers with 32 AT's. One with XR's on stand off boxes and one with XZ's without. Both are running Imco -2". Both in the 700hp range. The one with the XR's wore the gears out.. The one with the XZ's the uppers are still going strong. Not really an apples to apples. But my opinion has always been that if you dont have enough power to snap the teeth off of the helical gears, they will last longer. Both boats have been driven with respect, that is THE most important factor. A properly setup B1 with good top cap, will go a long way when driven with respect.
The lowers are better with the XR propshafts, especially if air time happens and you dont have the feel for driving in that type of water..
XR upper gears have been snapping teeth off in the past couple of years, where they weren't before that. Hopefully someone will solve that problem in the future..
If you want to put bigger power and drive it without respect.. Then you will be better to step up to a drive like the SCX..
But everything will break if you try hard enough..
If you have questions.. pm me or you can call me.
Hope this helps.
Dick

US1 Fountain 12-08-2009 10:17 PM


Originally Posted by Mr Gadgets (Post 3003049)
A properly setup B1 with good top cap, will go a long way when driven with respect.

Very true! And then sometimes even when abused.
A friend of mine took both of his mid 90's drives and made his own steel towers for the uppers and also his 1" thick AL billet caps. Studded the housing and never had a drive break yet. He is running huge power (don't know HP, other than it pushes his 32 Fever in the upper 90's) This was a good 3 yrs ago, still going strong. He is also using the original gears, not the upgraded X-gears. Last yr he was makeing a video of his boat in front of our marina and was going full throttle from a dead stop to test the drives and caps. He uses his boat as a test platform since he does the steel tower and custom caps as a sideline of his business. He knows just 1 speed when out running, and it ain't slow. :)

Mr Gadgets 12-08-2009 10:23 PM

I forgot to mention, I have been installing steel towers in the B1 cases for some time now.. I also can sleeve the snout where the pinion bearings wear into the case.. With the XR ribbed top cap that gives steel towers on both ends to locate the gear stack. External drive cooling and filtering helps keep the lube clean and cool for better operation..


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