Velvet Drive Problems

[Jango]

I have a Borg Warner, Velvet Drive 71C, 1:1 Gear. Transmission is turning a 12x16 non cupped prop at 6000 - 6500 rpm, probably less than 10% of running time. 90%+ of the time rpm,s are less than 5000.
Last time out in the Boat, speed was approx 2/3 of previous max of 85 - 90mph, while rpm,s remained max at 6500.
All I can conclude is tranny is SLIPPING although oil remains pink and NOT overly Hot. I realize rpm's are probably excessive, together with High HP, which is probably the cause. Also could a high Oil level be a Problem?
Any ideas on how to take care of this problem - different oil, cluthes, oil pump or do I need a larger trans - 72C
Thanks for any and ALL Help

Jango

[Frosty]

Sure your not cavitating exesively, ie damaged prop.

I assume that this is a surface prop.

I would think that at that RPM and high HP your gearbox would be very short lived if it slipped to that extent.

[Jango]

Thanks for your reply Frosty.

Prop is in excellent condition. Prior use of Boat, everything was great, 85 mph @ 6100 rpm - 2 people on Board

Conventional inboard, NOT surface Drive.

You may be right, the gearbox may be toasted. Although, I only ran at high rpm,s for a short time - couple of minutes. I did get up to almost 60 MPH, but should have been doing 90 at 6500 rpm.

All speeds are measured by GPS and should be accurate.

[Jango]

Found some answers:

1.HIGH RPM (6500) - No Problem

2.Additional Oil is actually a Plus - can fill as high as posible without overflowing out of vent.

3. 71C can Not easily be Modified to handle HIGH HP - MUST go to 72C (1018-002)