Exhaust flappers?

[lscray]

Our boat's in for winterization and they called today saying it needed exhaust flappers for $375. It's our first boat and we've only had it a few months - what are they and would they be hard to replace ourselves?

The boat's an '04 240SD.

Thanks

 

[JimG]

Flappers are a one way valve in the exhaust manifods... let exhaust exit, keep water from coming in. It is very important that they work properly. If they don't function, water can rush into your cylinders and cause a hydro-lock which can cause total engine failure in some cases. Replacement requires removing the manifold hoses... no too bad if you are a mechanic with tools. Being that you don't do your own winterizing, I'm thinking let the dealer do it.

 

[everthing's irie]

found this on the web http://www.boatequipmentsuperstore.com/Mercruiser-Exhaust-Flapper-Valves/

 

[lscray]

Thanks y'all. I figured they were something like that - not sure where they're located on our boat. I'll check it out when we get the boat back. I saw those flappers earlier today while sufing the web. I'll think I'll tackle it.

Anyone here ever done it and have any pointers?

Thanks again.

 

[JimG]

Thanks y'all. I figured they were something like that - not sure where they're located on our boat. I'll check it out when we get the boat back. I saw those flappers earlier today while sufing the web. I'll think I'll tackle it.

Anyone here ever done it and have any pointers?

Thanks again.

Fill in more information about your boat (motor, out drive, etc.) in your signature... it will help with your questions now and in the future. I am guessing a small block V8 with Alfa out-drive. There will be an exhaust riser on each side of the motor with large 4" (or so) hoses attached going to the back of the boat. The flappers are inside near the bottom of those hoses. I have not changed them myself but know approximately where they are. I'm sure someone here will shed more light.

 

[NorCal Boater]

Jim is right. If you follow the exhaust back from the riser down to the "Y" pipe the flappers are just on the engine or up side of the "Y". You just need to take off your exhaust hoses, pull the elbow and you should be able to reach them. Its a pretty easy job. I have done many. This link wiiill show you a picture.

http://www.justanswer.com/view_image.aspx?href=%2fuploads%2fROCKETBOAT%2f2008-12-02_035920_11.JPG

Have fun.
Shawn

 

[Beer Thirty]

good thread, i've got to replace mine as well. I found out they were bad the hard way. Luckily no damage was done.

 

[NorCal Boater]

I worked in a boat repair shop a half a dozen years ago while I was tryiing to decide what I wanted to be when I grew up....I was 50 at the time. Anyway, I changed a lot of these including the ones on my own boat.

They are rubber coated metal and what happens is the rubber eventually comes off. They may still slow down incoming water but won't stop it. Also old ones make noise as they open and close and if you know what to listen for you can hear them when they are bad.

It is a do-it-yourself project if you are patient and careful. You must be sure to get all the hose clamps back where they belong.

 

[Beer Thirty]

You must be sure to get all the hose clamps back where they belong.

so...... what your trying to say is that extra parts aren't a good thing? :grin:

 

[Jim240]

This might be applicable. Check the sticky for Mercruiser Service Manual 31. Check out pages 7B-4 and 5.

 

[NorCal Boater]

so...... what your trying to say is that extra parts aren't a good thing? :grin:

No....spare parts are never good. Except in the case of my knee replacement surgery a few weeks ago. The Doc had a few leftovers when he finished but they weren't much good.

 

[JimG]

They are rubber coated metal and what happens is the rubber eventually comes off. They may still slow down incoming water but won't stop it.

In more extreme cases (as in my brother-in-law's), the hinge rod can rust in two and the flapper fall down into the Y. Without knowing it happened he stopped quick when entering a no wake and water rushed the cylinders and killed the engine. When he tried to re-start, the engine blew a rod against the pressure of the hydro-lock. :smt089

 

[rondds]

After replacing an impeller (with every vane gone) on my friend's Maxum 3300, we decided to look for the broken pieces. Our search took us to the flappers. Pretty simple job that I would feel comfortable doing. As stated above, just involves taking stuff off and putting it back on properly. Taking digital photos BEFORE can be helpful if you aren't sure of orientation for putting stuff back together.