how fast can u spin a bravo xr?
01-04-2009 | 10:02 AM
#11
Registered
Joined: Feb 2002
Posts: 6,656
Likes: 20
From: Lake Michigan
I would most likely ask someone who might have alot experience with rebuilding these drives and thats all they do day in and day out. www.maxmachineworx.com also www.bravoshop.net Also their is a guy in Wisconsin that did or still does works in directly with mercruiser on just lower units. Its MPI . (rebuilt mercruiser sterndrives is all he does along with why they failed) I went to his class many years ago very smart guy about outdrives. I would have to look his # up. Also torque, props coming out of the water, full throttles starts, lack of maintenance, water intrusion, and of course impact all killers of outdrives.
I agree...
I will also say that water intrusion and setup/proper shimming and rolling TQ was my problem.
Once I corrected that and went with 3 blade props no more boom boom.
I did lose a bit of mid range and fuel mileage but If I need to run a long haul I throw on the 4 blades.
Last edited by Back4More; 01-04-2009 at 10:07 AM.
01-09-2009 | 04:42 AM
#14
Charter Member #601
Joined: Dec 2000
Posts: 3,276
Likes: 5
From: Holland, Mi USA.
Jason,
I used to run my standard bravo to 6300 consistently, but that was helical gears. I have run my XR with 300hrs on it to 6300, but not that many times. That was 565" 750hp in a 28' Checkmate Convincer, 6000lbs.
The amount of time you spend at above 6000rpms would be the key. The advantage of smaller prop to keep the torque off the drive, may be a better trade off, as opposed to limiting the amount of time above 6000rpm.
Setup on the drive is also critical at that high rpm. And drive oil temp is also a factor. So yes, it can be done. Yes if done too long or the drive isnt setup right, then no. Keep it at that rpm for extended periods, then no. Any garantees, NO.
But you may end up keeping that drive around longer, just for the fact that you are not adding load with a larger pitch prop.
Hope this helps.
Dick
I used to run my standard bravo to 6300 consistently, but that was helical gears. I have run my XR with 300hrs on it to 6300, but not that many times. That was 565" 750hp in a 28' Checkmate Convincer, 6000lbs.
The amount of time you spend at above 6000rpms would be the key. The advantage of smaller prop to keep the torque off the drive, may be a better trade off, as opposed to limiting the amount of time above 6000rpm.
Setup on the drive is also critical at that high rpm. And drive oil temp is also a factor. So yes, it can be done. Yes if done too long or the drive isnt setup right, then no. Keep it at that rpm for extended periods, then no. Any garantees, NO.
But you may end up keeping that drive around longer, just for the fact that you are not adding load with a larger pitch prop.
Hope this helps.
Dick
01-09-2009 | 09:31 PM
#15
Platinum Member
Joined: Dec 2002
Posts: 2,195
Likes: 2
From: Dallas, TX
I agree with Mr. Gadgets...lot's of variables with RPM just being one. We have a lot of time at 6000 RPM+ and the only thing we ever broke was the Merc stock top cap (10 yrs ago) on the port drive, this includes numerous APBA races.
With MMW modified Bravo's to XR+ standards including most of their upgrades, we have not had a drive failure and there has never even been any sign of significant wear evident on the magnets. Twin 750-800 HP, 30' vee, 28P Bravo 1's, 9,500-10,000 lbs depending on fuel load.
The list of items that I believe lead to a shortened Bravo drive life include:
High HP in a single engine vee
5-6 blade props
High pitch props (more operating time at elevated TQ)
High oil temps
Poor throttling
With MMW modified Bravo's to XR+ standards including most of their upgrades, we have not had a drive failure and there has never even been any sign of significant wear evident on the magnets. Twin 750-800 HP, 30' vee, 28P Bravo 1's, 9,500-10,000 lbs depending on fuel load.
The list of items that I believe lead to a shortened Bravo drive life include:
High HP in a single engine vee
5-6 blade props
High pitch props (more operating time at elevated TQ)
High oil temps
Poor throttling
