Velvet Drive Problems

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

 

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.

 

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.

 

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)