noise from engine/outdrive

[turbocorrado]

4.3 v6 with alpha 1 gen 2
so this motor and outdrive were on my other boat last season and swapped to this one. no issues at all last season. ive ran it in the driveway multiple times with no issues, went to put the boat in the water at the local ramp last week to check for leaks and let it run in the water for a bit, just floating it over the trailer for 20 minutes or so, if this went well i was gonna take it to bigger water and actually run it. about 5-10 minutes into it running a weird tapping noise started. didnt sound like it was from the engine. it sounded more behind the engine, like driveshaft/coupler area possibly. revving it up it increased with rpm but faded out, im not sure if the noise was going away or just couldnt hear it anymore over the engine.
i came home and ran it on the hose in the driveway again and the noise was still there. from in the boat it now sounded like it was in the outdrive, putting it in forward didnt change anything. i hopped down and it sounds like its coming out the exhaust, i took a video to capture the noise, what do you guys think?

http://vidmg.photobucket.com/albums/v600/nab627b/20170709_190228_zpsczsvvqvx.mp4

 

[turbocorrado]

im thinking next i should probably yank the outdrive and run it without that to see if the noise is still there

 

[Scott06]

Couldn't acess the video from the link but would assume it is exhaust shutters. I get a similar noise tapping after they get warm. check the upper part of the y pipe with a stethoscope or screwdriver to the ear. If you left the existing y on this boat this would explain why you didn't hear it last year

 

[AShipShow]

im thinking next i should probably yank the outdrive and run it without that to see if the noise is still there

I think you've already answered your own question... gotta pull the drive to isolate which half its coming from.

 

[turbocorrado]

havent worked on it due to vacation and a child. but i got back to it, isolated it to cyl 3. pulled the rocker arms and push rods, didnt see anything obvious, its only audible from the exhuast so im thinking something is up with the exhaust valve on cyl 3, gonna do a leak down test tomorrow and then go from there