Exhaust shutters

[philbullet]

What are they far? Is it to keep water from backing up into the exhaust?
That's my guest.
Thanks ahead.

 

[pnhigg]

Yep. Under certian circumstances water can backflow into the exhaust and even a cylinder which could then lead to some expensive issues. From what I understand it is not a likely occurance, but the shutters are to reduce the risk of it happening.
They are not difficult to change in most cases

 

[thumpar]

Yes they are to keep water out. The time when you would need them most is if your engine dies or you go from fast to slow without the engine running. The wave of water from behind would rush up the exhaust.

 

[philbullet]

Thanks,i guess i better get them in order,because i will be doing alot of backing up at idoling for what i use my boat for.

 

[Ostsideend]

Just in addition. Due to that these flapper valves are cheap just put them in. But the risk is very, very small that water will come through the z drive opening all the way up into the exhaust manifolds by stopping the boat into idel. (the exhaust gas of the running motor will still give a pressure against the opening!) There is much more risk if the boat is (i.e.) on anchor without the engine running, flipping arround in heavy weather with high waves that water can be pumped into the small slots of the Z drive passing up into the exhaust manifold.
Put them in, but dont do it too flurry.

 

[ktbarrentine]

You also need to take care when running the boat on muffs.... Follow the guidance of mercruiser service bulletin 99-09 (google it: http://www.boatfix.com/merc/bullet/99/99_09.PDF ) to reduce the possibility of water ingestion that may occur while running the engine at idle rpm on a Flush Attachment.