We were in a buddies 1991 Baja 240 with a 502 mag mpi and it was the second weekend since servicing the drive with Lucas full syn. M, no slam here on Lucus, I love thier products, but we were returning from a moderate run up river about 35 miles and he decides to come down on it hard and before it comes up to full speed something went wrong in the back, from lack of knowlage we both thought the thing spun a prop hub so that is the feel and sound we were getting, kind of a slipping/shuttering/wierd exhaust note, we were river boating and with the hub thing in mind we backed off but kept it on plane at light throttle, watched the gauges and come 25 miles home with the above symptoms, did not feel good but did not know if it would come back up on plane and we were minutes from dark on the ohio river.

After some educating on the prop we learned they don't spin hubs on this style prop. The coupler seems very happy and still looking like a new one in fact. U joints are tight and free, the oil came back out clean as a whistle.

The owner has a friend do all his props and he give him a # for a drive guy a couple of hours away and he said he has saw fully syn. oil allow the cone clutches to slip a few times.

This has not been fully determined but after going through everything else we are going to service the drive again by going back to the Merc. oil that has been keeping it happy sine 1991 when it was new, it has 250 hours on it now. And take it back to the river for a test run.

What do you guys think. Anyone here heard of this ???

Cone clutches are what puts the drive gears into forward or reverse. If one was bad, the drive would hesitate for maybe 5-10 seconds before engaging into gear. I have heard of different lubes causing this issue. Bravo drives do not slip an auto tranny or clutch. They are either in gear or they are not.

It sounds like a prop hub or coupler to me.

So do the cones have to carry the torque under power or just during the shifting, I did not completely understand,

Looking the design over through the cover plates and in pictorial views I thought they carried the torque and were engaged by shifting the driven male cone up or down to pick up the appropriate gear on top or bottom of the cluster to reverse direction of the vertical shaft ??? Thanks. !!!

Synthetic oil can make the clutch slip if the clutch is worn or if the set up height is not correct and it also needs to have the correct additives for steel on steel engagement. Once the drive is in gear the clutch and gear are under load the whole time.