possible simple fix for Bravo clutch wear, seeking thoughts...

[Mischief Managed]

I was thinking about why Bravo clutches start slipping or shifting funny and how it could be addressed inexpensively. It seem like the main cause is the fact that the clearance between the cone clutch and the cups inside the gears increases enough that the shift cam doesn't push the clutch into the cups as far as it did when the drive was new. I'm pretty sure the Mercruiser recommended fix is all new gears and cone clutch, but what if there was a simpler and cheaper way to take up the clearance?

If you study the shift cam assembly, it's easy to conclude that shimming the cams so that they stand a few thousands taller on the shift fork would make the cone clutch engage further up or down in its travel and therefore eat up the slack left by wear. The problem with that fix is that the shims would likely wrinkle and jam due to the way the cams slide on the fork. Instead, if a new fork was made with the cam faces a few thousandths thicker (while keeping the part that engages the cone clutch the same thickness), it would accomplish the same thing as shims, but without the danger of the shims being damaged and jamming. I don't think this fix would work if the clutch is already slipping under load, but if it were implemented shortly after the shifts started getting delayed, it could possibly double the life of the clutch. It would literally take 30 minutes or less to install if the drive was off and drained.

FWIW, my initial thought was to make cams with more lift, but that would be substantially more complex than just making a thicker flat steel part.

Thoughts?

 

[Scott Danforth]

they generally only wear out if they are run without lube or not fully engaged (bad adjustment). normally they last the life of the boat.

when the shift starts to get delayed, replace the worn shift cable

 

[kenny nunez]

Since Volvo drives used cone clutch engagement the fix when there was hesitation was to remove the cone clutch and either glass bead the surfaces or use lapping compound to remove the glaze that was causing the problem. Of course this is after checking out everything first. Also the wrong gear oil will cause this symptom.