B-Max
05-06-2011, 01:26 PM
#51
No, I don't think that would help at all.
05-06-2011, 01:46 PM
#53
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Pacalim- Jason is exactly right. These procharged motors don't make power like roots blower motors. Hp is directly proportionate to rpm like a naturally aspirated motor, as where positive displacement blowers make more bottom end torque. You'll notice on your boost gauge at cruise speeds that your probably always under at least some boost. I cruise at 70 at 3-4 lbs, and any throttle input from there is extremely responsive. This isn't good for drives. My best suggestion is to a) check your coupler. If your driveshaft won't slide in and out of the splines very smoothly, it will bind under trim conditions and put a load on the pinion bearing pack. B) if your using merc oil, change it every time you run the boat and check for metal. C) stop using merc oil, it's garbage. D) if you can't spend the money on an aftermarket drive, buy the good parts and talk to some of the builders about assembly technique. There are lots of tricks that can be done to prolong the life, but ultimately, xr drives are on borrowed time if you have any kind of power. Just my 2 cents boss.
05-06-2011, 01:55 PM
#54
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In my experience, royal purple was too slippery. I had clutch engagement issues with it. Are you running a 4 or 5 blade prop? What's your propshaft depth? If you want good oil, call John at the bravo shop and buy his neo oil. It works well so far as I can tell. I put some under a microscope today, and it's all still together. Merc oil separates under heavy load- it's called shearing, it physically separates the oil from itself and loses it's lubricity and film strength. Drive oil is meant to be a cushion between the gear teeth, as well as a lubricant. Your prop pitch is practically irrelevant. You want the motor to run smoothly in it's powerband without lugging the motor. Lugging causes detonation, and I can theorize that it causes more load on the drive, but I can't stand by that.
05-06-2011, 02:13 PM
#55
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Im running a 4 blade bravo 30 prop and a -2 Imco shortie lower.On a drive with xr top cap cryod X gears thick floor, steel tower. my drive failures useally occur right after a wot pull. seems like not much happening in last inch or two of throttle. no noticeable speed gain or rpm change. just a broken drive as i limp it back to the marina. thinking about SCX
05-06-2011, 02:58 PM
#58
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Ok, what is the consensus on drive oil? I have a Bravo in a light boat and 350 hp or so. With any luck, i will need to get some drive oil in it soon.
05-06-2011, 03:54 PM
#59
Geronimo36
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Im running a 4 blade bravo 30 prop and a -2 Imco shortie lower.On a drive with xr top cap cryod X gears thick floor, steel tower. my drive failures useally occur right after a wot pull. seems like not much happening in last inch or two of throttle. no noticeable speed gain or rpm change. just a broken drive as i limp it back to the marina. thinking about SCX
Torque loading the drive will cause bravo failures. Prop as high as you safely can with a bravo style drive, it'll help it live longer.
