1996 Mercury 250 EFI Noisy at 4000 rpm and up!

[fclay54]

Please watch Youtube video and let me know what you think it might be! Engine runs good 45 mph at 5500 rpm just noisy rattle!
Thank you for any ideas!

[boats.net]

It's hard for me to tell but it may be a burn out or broken exhaust tuner, might drop lower unit and look up in driveshaft housing to see if muffler is broken or holes in it.

[fclay54]

Sounds good I will drop the lower unit thanks

[fclay54]

With the lower unit off and running engine, I have exhaust out of main exhaust port. Should I have exhaust coming out of the back port also? The rear of shaft housing was getting very hot. Thanks
Floyd 770 715 8106

[boats.net]

With lower unit exhaust will only come out of lower housing. Usually you will find parts of muffler laying on lower unit when you remove it if muffler is bad.