Exhaust Shutter Question

[gtdavis]

Ive got a weird rattle/tapping sound comming from ?back? of motor... cant hear it at idle or on muffs, seems to be a little more noticable when in gear. I figured I would start with the shutter..... I took the pipe apart all that is left is the cross bar that held the flappers?? can the old parts make it out through the system or could they be stuck somewhere creating the noise?? Do I need to look elswhere for the noise? Otherwise runs and pulls great? Thanks

1994 mercruiser 3.0 electronic ign
Alpha I

 

[Brentathon]

Re: Exhaust Shutter Question

I found a "piece" of one of my shutter plates all the way down in the hub area of my outdrive, when I took the prop off one time.
That's how I new I needed to change mine.
Eventually, I replaced the outdrive, engine, and Y-pipe, so I have no worries of any shutter piece being stuck somewhere...now.

 

[stonyloam]

Re: Exhaust Shutter Question

...can the old parts make it out through the system or could they be stuck somewhere creating the noise?? Do I need to look elswhere for the noise? Otherwise runs and pulls great? Thanks
Alpha I

No the pieces (rubber coated steel) are in there unless the outdrive has been removed after they broke off. The noise..... maybe. Good luck.

 

[EddiePetty]

Re: Exhaust Shutter Question

...here's a couple of links to previous post WITH PICTURES of the treasures found in the exhaust passages:

http://i266.photobucket.com/albums/ii279/gofastcrazy/boat stuff/DSCN1224.jpg

http://forums.iboats.com/showthread.php?t=293681&highlight=shutter

 

[gtdavis]

Re: Exhaust Shutter Question

So...I prolly need to pull the drive and make sure nothing is stuck.....Could it be the flappers still rattling around making a noise??? Gonna take them out anyway.....should I look for anything else while I have it off the could be the source of the noise.... I've decided I really dont like noises!:redface:

 

[Brentathon]

Re: Exhaust Shutter Question

My previous boat had a knocking/rapping noise from back of motor.....turned out to be a gimbal bearing that was on its way out.
When you have drive off, reach in and spin that bearing.......should feel super-smooth (technical term).

 

[jerryjerry05]

Re: Exhaust Shutter Question

You need to replace the flapper.It probably got hot and melted.
It supposed to stop water from comming back into the exhaust on sudden de-celeration.
While you have the drive off you might as well check out tthe bearing and alignment.J

 

[Don S]

Re: Exhaust Shutter Question

Normally, if a shutter has the rubber burned off, they will rattle a little at idle when they have time to open and close. When the rpm raise, the sound usually stops because the increase in exhaust doesn't allow them time to go back to the closed position and hit metal.
I would be thinking more of a gimbal bearing or ujoints making noise when you increase rpm's.
Might be well worth your time to pull the drive and check things out. How long has it been since the drive was off and the bellows checked for water, and the alignment checked and splines greased?

 

[gtdavis]

Re: Exhaust Shutter Question

Honestly Don Im the second owner I have only had this boat less than a year..... So I honestly have no clue..... I did some general tune up things but it has mostly been to the motor prolly should have done more but wanted to get it on the water (Yes I read your quote about doing it right the first time :redface: ). The motor was rebuilt in 07 but I dont think anything was done to the drive unit (sometimes I wish I had my little 50hp thundorbolt back ) In saying that I have pretty much resolved myself to calling it a season and pull the drive for a winter project to redo all the stuff that needs redoing. All the bellows and such look ok but I know that doesnt mean anything. Any tips on "must replace" items while I have it off so I can get an initial parts list going and just add to it if I need to??
Thanks Again!!

Oh and Brent....Those are the kind of technical terms I like.... easy to understand!! LOL

 

[stonyloam]

Re: Exhaust Shutter Question

If the drive was off in 07, the shutter pieces may be long gone, but you should replace the shutters, they are important to keep water from backing up the exhaust into the manifold when your transom is hit by a big wave (launch or sudden stop). Good luck.