Question about exhaust flaps.
 

Are they nessessary in my case? The after market silent choice tip has one built in. I think they effect the sound, look like crap and turn the exhaust hit the transom sides and turn it yellow/brown.

http://i51.tinypic.com/10h8sgl.jpg

http://i56.tinypic.com/213hdgj.jpg

http://i52.tinypic.com/2eki5h5.jpg

You don't need the external flapper as long as you have an operable internal flapper.

I have the same internal flappers as you. I was debating about putting the external flappers on too. My transon is black so they would not be as noticable.

I imagine they distort the sound (which I enjoy) a bit.

Update: Ran at idle with and with out. They do sound better without them. With them they cycle loading up then dumping water while almost sounding like they are going under water.

I don't believe that type of tip needs them or came with them.

We use the external flaps on a 25 Elim Cat, and they seem to help stop the spray of water coming up and misting over the back transom or hatch area bcuz its above the water line,, especially in reverse......

They are doing the oppistie for me. My transom is resessed and the flaps deflect the gasses toward the glass. Without them the exhaust would blow straight out.

Do you trailer your boat or leave it in the water?

I had the internal flappers in my boat and both flappers burnt out . A real bad metal on metal knocking sound ensued. I had them taken out and had the tips laser cut as I found that the exhaust was reduced to less than 3 inches beyond the flapper and wasn't needed. I think if you leave your boat in the water you may want them to eliminate any water back flowing into the exhaust. If you take your boat out every time you use it , you may not need them.

Always trailer. Never in the water longer than 7-8 hours.

Q&Q helps reduce the possibility of water washing in and over the hump since it will dump down the Y-pipe instead. If you don't have Q&Q it might be wise to keep both flappers! All JMO, I'm no expert on this.

According to Mercury, you need the outside flaps even if you have the internal ones. Don't chance it, use the external flaps.

I forgot to say this..... I do have the external flaps on mine. I think you need to have these.

I have both sets on my scarab ! would not take a chance of having a problem because they don't look good!!!!If your boat sits as low as mine does ,nobody is going to see them any way.Swim platform covers them up most of the time......


Jim

The guys telling you to keep them on as a redundancy are correct if you lose an internal flapper, you run the risk of engine damage on start up. Have You thought about switching out the tips for a longer tip with a no burn internal flapper? Would get the spray and exhaust further away.

what if you have external flappers do you still need internal?

Well, i'm pretty much worse off than the begining of this thread.... If I have the internal flaps (in perfect shape and working order) do I acctually have to have the Outters too? It doesnt seem right to need both??

Sheer, I have had three boats with only internal flappers and no problems. My internal flappers were not like the ones in your pics. All of my tips internal flappers were and are stainless steel plates that pivot inside the tip. I am confident with these type of tips against backwash when parked or shutting down. If it was mine and I was confident that the type of flapper you have will not fail, then I would just use the internal. I still check my internal flappers on occasion to make sure they are closed when the engines are off.

If you have internal flappers, you really don't need the extrenal ones.
I have basically dry exhaust and don't have any flappers. I do have switchable external mufflers. When I dock or anchor, I just make sure to close the flaps on the mufflers.

I'm wondering if those tips come with the external flappers too? Doesn't look like it based on this....

http://www.mercuryracing.com/accesso...xhausttips.php

The previous owner of my boat gave me a set of externals too. I don't know if they came with the tips or he bought them seperate.

BTW, I had to replace one of my internal flappers and the boat doesn't have a lot of hours on it. The rubber was fine, but the metal part broke.

If you lock up a motor because of injesting water you'll kick yourself in the a$$.. you cant see them when your driving..

I know these cost about 10 times as much, but they are better looking.

http://www.keitheickert.com/p-12578-...-flappers.aspx


Just a thought

Man,
You weren't kidding when you said 10X's as much!:eek:

SI,
If it were me, I'd keep both, especially if you ever anchor is water where there are large wakes/waves, it will help keep water out. I have both on the Nordic.
Dean

I know, I couldn't get over the price, especially if you have a twin application. Kind of suprised no one else has made something similar.....they do look much better, but for that coin I would rather do many other things.

How far above the water line are your exhaust?

If they are not that far above the water line I would keep them on. The closer they are to the water line the more likely you may come across a situation where there may be water forced back up there (i.e. in reverse, idling in water where a wave can get you from behind).

I looked up the tips and silent choice. CMI Custom Marine. On the reciept it even says with internal flappers? Im suspecting the installer just put them on because they where on the old stock tips?

Larry I have been in Mexico for the last few weeks and just saw this thread. When I had the Silent choice installed last year I had the tips replaced at the same time. They came with both the internal and external flappers.

I left the external ones on because I learned the hard way and lost a motor on my last boat from a flapper failure...