New (used) muffler.. which way is up?

[Outrageous]

Originally Posted by ct9amr

You may want to check your engine specificatiosn befor installing it and creating more back pressure.
Move of those V8's call for dual 3" out and you may cause yourself more issues installing the muffler above.

You may need something like this.



This is what i did to my old shamrock as a fix and it worked well at slow speeds.
I used silicone turn downs, double clamped.
http://static.flickr.com/36/87782627_e900685110.jpg?v=0

CT9 that's a trick looking setup how is the noise at cruise. Where did you get those muffs? Save on fuel with those?

[deepsushi]

Outrageous -- After reading your post about your muffler I took a closer look at mine. The inlet's definitely have a slight upward slope to them which I had not noticed upon initial inspection. This would place the exhaust outlet on top. I really appreciate your input. Now the question is if I will get lucky and have the space to slide the muffler in place without having to pull the rear deck.

My boat has a tired 454 crusader in it that I will replace when the funds become available. I cruise generally around 20- 22 knots and I suspect I get around 1mpg as 454's were not designed with fuel economy in mind. If I were to repower I would replace it with a 350 as the inboards with this motor combo seem to cruise at the same speed with better economy. If you want to go faster you need to go diesel and the yanmar powered boats cruise around 25 knots or higher.

CT -- Thanks for your input. The shamrock bilge is huge compared to the space available in the seacraft. I don't know if there is even enough space to fit two mufflers inside. My current exhaust is Y'd into a single 4" exhaust as it is. Other inboard seacrafts have used this muffler setup throughout their lifespan ( over 30 years now) and this leads me to think that the setup probably works out ok.

[Outrageous]

I don't know to much about The inboard setups when it comes to mufflers as I have always been a sport boat nut with through hull exhaust. The more I look at this setup the more questions I have. A mock up of mine has the muffler lower on the engine side than it is at the aft end. (Seems it should be lower on the rear) It is also not centered very well (a few inches favoring port) What happens in the winter when below freezing? There isn't a drain on this thing, maybe I should add one. As far as being able to get it in without pulling the floor up I would think you would have to be real lucky. I have fuel tanks out as I an replacing them along with the floor and its still a pain to see whats going on as far as support under the muff. You maybe better off to start after the fishing season ends. I have a 350 going in that will be about 315 or 320HP. Hope to be pretty fuel efficient.