Tartan S/S standpipe exhaust in C&C Corvette

[67c&ccorv]

Don,

Wondering about the feasibility of installing the MMI S/S Tartan standpipe exhaust in my 1967 C&C Corvette?

Instead of the exhaust exiting out of the side of the boat as on a Tartan it would run approximately 10ft on a slight upward slope to a gooseneck or loop and then down and out the rear transom.

The old copper-jacketed exhaust is a heavy behemoth and takes up a lot of space that I could put to better use.

Any thoughts?

[Don Moyer]

I don't claim any engineering expertise in the dynamics of fluid flow through an enclosed system, but we do have considerable feedback from customers to indicate that anytime an exhaust hose goes through multiple peaks and valleys after it starts down from the high point just downstream of a water lift muffler or standpipe, exhaust back pressure will elevate somewhat with each peak. It appears that each peak and valley functions as an additional "water lift" device, and the elevation of back pressure seems to be accumulative between each such peak and valley.

In your particular application, the "slight" elevation in the hose between the standpipe and the transom might be tolerable, but I'd worry about the additional loop just before the exhaust exits.

Beyond this rudimentary understanding of the principles involved, it's very difficult to accurately calculate beforehand what amount of "peaking and valleying" any particular application will tolerate. But, relying again on considerable customer feedback, a reliable indicator of a properly functioning exhaust system (after the fact of a system change) is to observe the flow of engine cooling water leaving with the exhaust at your highest normal cruising power setting. The water should be seen to flow out evenly with the exhaust, not "batching" (stopping and starting) as is quite common at idle. If you note even a subtle stopping and starting of the water flow while cruising, some elevation of exhaust back pressure is no doubt taking place.

Don

[tartansailboat]

Tartan S/S standpipe

I replaced my original copper standpipe in my Tartan 30 with Don's SS water lift muffler for about half the price of the SS Standpipe. Takes up a lot less room and works fine. There may be an advantage with the SS standpipe in that the water flow is less likely to back up into the engine if there is a starting problem but so far I have not seen that.

[hanleyclifford]

67 - I remember how we thrashed this exhaust business around earlier and remember noting that the water jacketed system that you have is the most efficient practical alternative, from the engine's point of view. The standpipe concept is the second best but relies on the downhill flow from the standpipe - the essence of it's advantage over the waterlift concept which in my view is (the) last (practical) choice, but the one (unfortunately) that most of us are left with. As I said earlier, I would love to have the system you currently enjoy, but I can certainly understand if space considerations are great enough to override engine efficiency.

[67c&ccorv]

67 - I remember how we thrashed this exhaust business around earlier and remember noting that the water jacketed system that you have is the most efficient practical alternative, from the engine's point of view. The standpipe concept is the second best but relies on the downhill flow from the standpipe - the essence of it's advantage over the waterlift concept which in my view is (the) last (practical) choice, but the one (unfortunately) that most of us are left with. As I said earlier, I would love to have the system you currently enjoy, but I can certainly understand if space considerations are great enough to override engine efficiency.

Agreed Hanley - the engine exhaust never has to push the water until it is injected into the very last section of the exhaust loop at the transom. The water injected into the copper jacket exhaust cools the exhaust without actually mixing with it.

It must be quite a load for the water pump but the system has worked well so far...it's just that the copper jacketed exhaust interferes with a number of systems (fuel tank, engine water intake etc.) and I would like to do away with it...maybe I will just go with the standard waterlift?

Thanks for your thoughts.

Cheers!

[hanleyclifford]

67 - I have been kicking this idea around in my head for a variation. How about a copper jacketed exhaust cooler exiting straight out of the engine, like yours, but shorter yet fat enough to cool the gases to the point where an ordinary exhaust hose could carry them up to the transom and out. The cooling water from the jacket could be discharged overboard at the most convenient location. What say ye?

[67c&ccorv]

I was actually thinking of going the opposite direction Hanley;

...making the water jacketed section longer and slimmer in diameter but still containing the same amount of water.

That might help with clearance issues and spread the weight of the waterjacketed section over a greater area.

When I drain the thing for winter layup a lot of water comes out of it!

Cheers!

[ndutton]

When researching a planned modification to the exhaust system, it might be a good idea to visit the USCG requirements on the subject to be sure your finished system complies.

Here is an excerpt that specifically addresses part of the discussion in this thread:

46 CFR Ch. I (10–1–10 Edition)
§ 182.425

(1) Water for cooling the exhaust pipe must be obtained from the engine cooling water system or a separate engine driven pump.
(2) Water for cooling the exhaust pipe, other than a vertical exhaust, must be injected into the exhaust system as near to the engine manifold as practicable. The water must pass through the entire length of the exhaust pipe.

In item 2, I interpret "injected into the exhaust system" to include water jacketed exhausts as a "system."

Hope this is helpful.

[hanleyclifford]

Good catch Neil. That appears to exclude my idea from the USCG point of view, though I'm sure I could make it work.

[roadnsky]

Good catch Neil. That appears to exclude my idea from the USCG point of view, though I'm sure I could make it work.

Hanley-
Are you suggesting you'd be able to "bribe" a Coastie?!
Just kidding, just kidding...

[hanleyclifford]

The coasties are more interested in your "no discharge" plaque over the pottie.

[sastanley]

The coasties are more interested in your "no discharge" plaque over the pottie.

Uh oh, is that where it's supposed to be? Do you think they'd bother to let me show them that the plumbing doesn't even route overboard?

[hanleyclifford]

I got a gig on this just outside of Deltaville once. The plaque has to be displayed in both head AND engine room.

[sailbristol]

which one?

which plackard the oil or the garbage or the drug?

[ArtJ]

I got a gig on this just outside of Deltaville once. The plaque has to be displayed in both head AND engine room.

Just a thought- Maybe the engine discharge should be a rubber hose laid
in the head bowl !!! Would save a plaque. ( only kidding)