Dual Exhaust conversion

[M3Fan]

A little off topic, but what's the reason CC opts for single exhaust outlets? Is it another way to balance out the wake or is there another reason? Didn't they do doual exhaust outlets on some Air Nautiques in the early 2000s? Just curious.

The single exhaust is a result of CC's quest for the quietest inboard out there, which I believe they have achieved BY FAR. In 1989 they partnered with a company called Vernay to create a custom muffler system for their boats. These mufflers worked great, and most are still in service today with no problems. MC and Bu tried this in the early 90's but gave it up (MC's was the "silent master" and I forget Bu's attempt. I've heard both were awful systems reliability-wise). The single exhaust also allows for a large tiller arm on the rudder- maybe this makes for smoother steering, who knows. In 97 they switched to another custom muffler- the Centek Hull Hugger. Same basic concept, but more compact. Developing a custom exhaust system to keep their boats quiet is one of those things that I have to admire CC for over the other brands. The result is a much quieter boat and much happier neighbors during those early morning runs.

[DanielC]

CC runs single exhaust for a couple of reasons. A single exhaust is quieter, and cost less to manufacture, and leaves room for the rudder cable on the other side of the bilge. On a V-drive boat, the hull is deeper, and there is more room for the exhaust plumbing, and a dual exhaust is easier to build in. There is a much shorter run to the transom, also.
Most direct drive boats with dual exhaust have only 3 inch pipes, so total exhaust pipe area is about 14.1 square inches, A Correct Craft boat with a single 4 inch pipe has about 12.6 square inches pipe area. Take into account lower flow next to the edges of the pipes, and I bet a single 4 inch exhaust actually flows more exhaust than dual 3 inch pipes.
I have seen some Ski Nautique 196's with the Python motor in them. They had the dual 4 inch exhaust.

[TRBenj]

Doug, the tips look similar, but these are 4" where I believe the MC pieces are 3". Mine have internal flappers, but theyre not real close to the tip. There are no mufflers, baffles or silencers anywhere in the system- its a straight through design for now.

I'll get a sound clip up at some point. The boat will be getting carpet and interior in the coming weeks, so it wont see the water again just yet. I'd liken the sound to a '70 CC Mustang with a Holman-Moody 302, only a little louder.

[NautiqueJeff]

Didn't they do dual exhaust outlets on some Air Nautiques in the early 2000s? Just curious.

The only modern Nautiques to have dual exhaust were the ones with the Python engine. Everything else has the single outlet.

[TRBenj]

The only modern Nautiques to have dual exhaust were the ones with the Python engine. Everything else has the single outlet.

Correct... at least officially. There were a few oddballs built or converted by the factory, or by dealerships.

GT40 with dual exhaust at White Lake

[SquamInboards]

Did you order those manifolds from that Ausie company? Ive drooled over those things but can't find it in me to shell out the cash. Would definitely like to hear your set up though.

[TRBenj]

Did you order those manifolds from that Ausie company? Ive drooled over those things but can't find it in me to shell out the cash. Would definitely like to hear your set up though.

Yes, these are them. Not cheap but theyre a nice piece. In addition to the performance increase, they weigh less (40 lbs per side) and will last forever.

If you want to hear it, just listen real hard. You can probably hear me from NH.

[east tx skier]

M3, DanielC, and Tim, thanks for the responses. Interesting stuff for sure. As far as the silent master muffler, I presume you're talking about the big one that connected to two pipes as opposed to the dual inline mufflers they used from 92 and above. I don't have any experience with the former, but the inline mufflers on my boat have been reliable enough (although they aren't a picture of silence or anything like that). That is to say, I haven't sprung a leak yet (knock wood).

[M3Fan]

As far as the silent master muffler, I presume you're talking about the big one that connected to two pipes as opposed to the dual inline mufflers they used from 92 and above.

Right on.

As a side note, I'm a huge fan of those 91-94 MCs. Awesome looking boat.

[east tx skier]

Thanks. She's been a good one thus far (once I through that awful 4010 carb in the lake).

I'm a big 196 fan as well.

[Andrew]

Re: RE: Dual Exhaust conversion

???? no backpressure will result in a significant loss of low end power! i don't know too much about pipe sizing when u have under water exhaust, but in the automotive world, i 3" single exhaust is about the sweet spot for the medium size v8 that u find in nautiques..... if cc had the hp/torque levels close to optimum performance, then ur probably gonna notice a drop in ur holeshot. u'll gain a good bit of power on the top end but imo top end is pretty insignificant unless ur barefooting....

Not exactly. To quote an expert:

Just to clear things up (and this comes up ALOT) no amount of back pressure in an exhaust system is "good". It doesn't add anything...well, other than to add to overall pumping losses of the engine. If an engine runs better with back pressure it is because the ancillary systems have been tuned to take into account the exhaust system that is adding the back pressure. If you remove the back pressure (i.e. the exhaust system) and then re-tune the engine for the free flowing exhaust it will make more power than it did with the restrictive exhaust.

This is exhaust theory in its most simplistic form...I'm not referring to 12" long zoomie pipes but full length exhaust systems. Backpressure doesn’t add torque or low end...no matter what you've been told over the years by shade tree mechanics. Your boat is no exception to this rule.

With the new exhaust, Ive made some gains on the top end (more to come as I dial in the carb) but Ive seen a bigger improvement in holeshot. Ive picked up 400 RPM going to WOT from idle- I now get a solid 3600 RPM with my Acme 470. The motor makes the most power/torque in the midrange (2500-4500 RPM).

I do barefoot, by the way- and I foot with some pretty big guys that like to go fast (45-46 mph). That shouldnt be a problem now.

ah, i missed the post where u listed all of ur performance mods. i was "***"uming that this was on a basically stock motor

[gldslope]

Just converted my 08 to Dual exhaust.

[Mikeski]

GLDSLOPE, please re-post pix and performance results. What motor, I have considered this on my 211 to help with barefooting (along with supercharging or a complete hiperf motor buildup). For now it just barely meets the demands with lots of compromise on my part.

[gldslope]

2008 211 Dual Exhaust

Here are some of the pics during the project. The exhaust outlet on the left is the original. Drilled a matching hole on the right side. Installed stainless tips, purchased some mandrel bent stainless tubing (.065 wall), did a lot of careful measuring, cut tubing with band saw, welded with my miller syncrowave 200 TIG. Have not run boat yet, that's next week!

Here are the pics hosted on my server...

http://www.petesdomain.info/dual_exhaust/pics.html

[bhectus]

LOL!! "Baby! There's water and stuff drippin' out!"

Nice job man, looks and sounds incredible.