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

After a some long fishing trips where I spent the day trolling I realized that the v-8 growl out the straight exhaust on the inboard was too overwhelming. I started looking for a muffler and low and behold the right one popped up on Ebay and it is now mine!

The muffler has dual 3" inlets and a 4" outlet which is offset. My question is which way is the proper orientation to install it? I can see the baffles inside
the muffler and my guess is that the outlet needs to be mounted on top so that the gases pass through the trapped water. Anyone know if this is correct?

I have the same issue on a 23 inboard restoration project. The boat was a basket case when purchased but the muffler that came with it looks like what you have in the picture. Being below the floor I would assume that it is full of water until on plain when it would continually drain itself. I would imagine that the original configuration had this some type of mounting or attaching to the hull to eliminate vibration. Anybody have any pictures of an original setup or knowledge of how they work? Mine has two 4" inlets and one 4" outlet.

You can see some pictures of how the muffler is setup on page 3 of member miles offshore rebuild thread here: http://www.classicseacraft.com/commu...ad.php?t=16894

My boat despite not having a muffler actually has the mounting brackets for a muffler which are plywood brackets with half circle cut outs for the muffler to rest in.

Thanks for the input! Its good to see what other people go through for there boats makes me feel sane! LOL

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.

http://i989.photobucket.com/albums/a...r/newstuff.jpg

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

Deep, took a closer look at mine today and it was rigged with the inlets and outlets closer to the top. It looks like you are right the baffles divert the gases into water to kill the noise. Hope this helps what kind of power do you have? speeds, fuel consumption ect.

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

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.

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.

Try the exhaust turn downs outside the hull before the muffler deal. I removed the flappers and put on 45 degree units and pointed it under water while running slow.

This was a huge improvment and I never isntalled mufflers after that.
At WOT the turn down are above water sot here is no restriction.

Check out fish the classi for lots of ideas on making yours managable.
A lot of people end of putting sound deadoning inside the engine cover as well.

What is fish the classi? I like the idea of low backpressure that equals HP and fuel economy. Can you post some pictures of your set up? I would like quiet too. Thanks, Steve

fishtheclassic.net is the shamrock forum. Lots of good ideas from guys who deal with inboards. The group is great.

I don't have a picture of my setup since I sold the boat a few years ago.
I bought some silicone connections that I clamped onto my exhaust after removing the flapper. They are pictured below, but you need to get them long enough so they are under water while under way.

http://www.maperformance.com/images/P/map_HOSE-112.jpg

I also looked at something like this but it seemed like I a lot of work to accomplish the same thing.

http://photos.wakeboarder.com/data/3...cture_0031.jpg

Finally got to run the boat with the new muffler installed. Made a huge difference in the noise level and was much more pleasant while trolling and while underway running we could easily talk at normal conversation levels.

Had a little snafu with the original used muffler as when I hooked it up the muffler leaked due to the inlet tubes having multiple cracks hairline cracks. Most likely someone over tightened the exhaust clamps and cracked them. Fortunately, another NOS muffler appeared on Ebay and I bought that one. The new muffler had the original sticker on it with "this side up" marked on it which confirmed that I was correct with my my original guess as top.

So how did it work after running for the season? Any issues? Hope you caught some fish!

The new muffler worked out well and I really noticed the reduced noise from the muffler. No issues at all and the motor ran fine with it.

Had a problem with the motor in the midst of the season and it would stumble and bog at anything over 2600 RPMS. Took me about three weekends to diagnose and the problem was resolved after I rebuilt (my first) quadrajet carb. In the midst of troubleshooting my engine the distributor decided to die as well so at one point I was diagnosing two issues at the same time which made for some real WTF moments!

Unfortunately, my engine problems coincided with our local inshore bluefin bite and once I fixed my issues the fish had moved down Cape! Other than that did a lot of bass / blues and bottom fishing with the kids. We have had a pretty great late summer and early fall with the false albies.

Biggest improvement I made was I increased my prop to a 17 X 17 from the crappy 16 X 15. I picked up almost 3 knots of speed at cruise and now am able to run 20 -22 knots at 2950 rpm which makes the fuel burn drop significantly down to around 10-11 gallons an hour. On the old prop I had to run it up to 3150 to get that cruise speed. Now if push it up to that RPM I get a pretty consistent 25 knot cruise. Only downside is the bigger prop does create a fair amount of prop rumble that is definitely noticeable.

Glad to hear you got it dialed in. How much clearance do you have in the tunnel with the 17"? nice performance numbers.. Those qjets aren't as bad to rebuild after you do it a few times and get the hang of them. Too bad about the timing it would figure that it would happen during prime fishing..

I forget the exact clearance with the 17 prop but I remember measuring it at one point and it falls within the recommended 10-15% of prop diameter. The prop does have a rumble to it now but at this point the performance gains are well worth the increased noise. The prop I used was an old school Federal equipoise. I would bet that one of the newer CNC props made by ACME or a Michigan DJX would probably perform as well in a 16" diameter.

Quadrajet rebuild was a lot easier than I thought it would be. There are some excellent videos on youtube that I used to guide me. Only part that was a challenge was figuring out the float height / installation. First time I installed it I put it on and the float must of stuck as gas started pouring out of the carb. Took it off tore it back apart and adjusted the float and then I was good to go.

deep,

Thanks for the info on the prop. Checked out the YouTube thing as well. Great resource for DYI. If you need any tech support or info check out Quadrajetparts.com. Best source I have found for parts and info on these carbs. If you need any BBC parts let me know I have a bunch.