Looks like something is wrong w/ one of my outdrives.
Was about to run a poker run, opened to motor hatch while idling in gear and heard knocking. Troubleshooting - found out it is not the motor.
One of my drives knocks in forward. Put in neutral or reverse - it sounds fine. Back into fwd and the knocking occurs. The drive works; I ran back home 10 miles or so on plane 3500. After coming off plane - knocking was same - no worse.

What is the likely cause?

Check drive oil for contaminants. If lube is clean then you may have prop slap which is not a detrimental issue. Upgrade to a flo-torque type hub design. Not applicable to SSM'S if thats what your spinning.

What drives?

It is not the props.
Bravo XR's.
I'm thinking I chipped a tooth. . .

Thats what it sounds like.Pull the top cap and see whats going on.

Pulled top cap - metal chips everywhere. Didn't dig any further.
Looks like front seal behind U-joint let go too. Leaks oil from there.
Off to get fixed . . . . . . .

Bill, just curious as to what kind of power you're running in front of those XR's and how many hours you have on the drives? Thanks

I think he has 575's ??

Just went through this. Took a tooth clean off a gear in the upper and heard the ticking. Not too much for fragments in the oil, but broken piece did make it into the lower gears and put a mark in them.
New gears and bearings.
Quiet mufflers saved me from grenading the whole unit.
XR behind 950 hp. Lived 35 hrs. RIP!

Kaama,

575SCi's that have 628 HP.
The upper part of drive has maybe 150-200 hours. The hours on the lowers is unknown.
Dropped the drive off w/ Excursion and he'll check them tonight.