Clanging noise in upper midshaft area

Motor is a 1999 Merc 200 EFI

Was about 500 yards from the ramp and running about 40 mph and all of a sudden a loud clanging noise coming from the upper part of the midshaft.....Thought I snapped a rod but enginge starts fine and goes in and out of gear fine and prop is not turning when in neutral. So I ruled out a drive shaft bearing and a drive shaft breakage. Only thing I can think of it being is the exhaust pipes running down that maybe one of them broke or blew a hole in the can not really sure any ideas? Got the boat Tuesday and it is already in the shop http://www.bassboatcentral.com/smileys/mad.gif http://www.bassboatcentral.com/smileys/mad.gif http://www.bassboatcentral.com/smileys/mad.gif http://www.bassboatcentral.com/smileys/mad.gif http://www.bassboatcentral.com/smileys/mad.gif http://www.bassboatcentral.com/smileys/mad.gif http://www.bassboatcentral.com/smileys/mad.gif http://www.bassboatcentral.com/smileys/mad.gif http://www.bassboatcentral.com/smileys/mad.gif http://www.bassboatcentral.com/smileys/mad.gif http://www.bassboatcentral.com/smileys/mad.gif http://www.bassboatcentral.com/smileys/mad.gif http://www.bassboatcentral.com/smileys/mad.gif http://www.bassboatcentral.com/smileys/mad.gif http://www.bassboatcentral.com/smileys/mad.gif http://www.bassboatcentral.com/smileys/mad.gif http://www.bassboatcentral.com/smileys/mad.gif http://www.bassboatcentral.com/smileys/mad.gif http://www.bassboatcentral.com/smileys/mad.gif http://www.bassboatcentral.com/smileys/mad.gif
Hopefully it is not something major and can be a somewhat cheap fix. If you put your hand over the exhaust port on the midshaft area the noise gets quite but when you remove your hand it sound like someone is in the mid shaft area beating from the inside out with hammer

Remove the gearcase- reach up into the driveshaft housing with a long pry-bar and see if the exhaust tuner is still properly attached. http://www.bassboatcentral.com/smileys/wink.gif

If it IS properly attached... sample the gear lube (look for signs of water, metallic fragments, or metallic sheen in the gear lube).

it is at the shop right now getting looked at.....If it is the tuner loose how hard of a fix is that and how expensive any parts needed or does a couple of bolts just need to be tightened back up?

Unfortunately- if it's the tuner, that's a very labor intensive repair.

Powerhead and Adapter Plate must be removed to properly address. http://www.bassboatcentral.com/smileys/ohwell.gif

will it hurt anything to run it with the tuner loose? I am not talking forever. I have a club TX this weekend then after that I will have about 3 weeks to get it fixed before I leave for the everstart on seminole.

Although I've known of engines that ran for extended periods with the tuner "loose" in the midsection... they did not run well (some wouldn't even plane off)- and wear occurred to metal components that were rattling against each other (requiring replacement of additional components). http://www.bassboatcentral.com/smileys/eyes.gif

Your choice, of course- but I'd get it addressed promptly, if it's indeed "loose".