Exhaust Guru's

[cal_d_44]

Hi all, I own a 40 ft Steel Centre Cockpit Ketch and I am in the middle of a refit and repower. Just starting to design the wet exhaust (See diagram) the top of the engine is 15 cm below the waterline and the bottom of the engine sits just above the built in fuel tank so there is no room to fit a water lock muffler there.

The plan is to fit a 60mm diameter exhaust riser to bend 60 cm above the waterline, inject the raw water on the downward side of exhaust riser. It will then drop 30 cm in to a water lock muffler, exit the muffler and flow down to the exhaust outlet on the side of the hull. There is a gate valve fitted at the hull which is shut off when sailing and healing to port. I will also fit a drain to the water lock muffler so after motoring it can drain before sailing and this should stop residual water in the water lock muffler running back to the exhaust riser when healing to starboard (not that I think it will).

Can anyone see any issues with this set up?

Regards

Cal

[georgelieber]

Any water coming in through the engine exhaust valves kills the engine and can sink the boat. My exhaust outlet is high enough to be out of the water regardless of angle of heel. I think this is great insurance on a voyaging boat. If you are starting from scratch on your exhaust set-up, now is the time to move the outlet to a high and dry location. On a steel boat it is easy to move holes around. Remember you may not just be heeling when sailing in good conditions... you may be heeling because the mast is broken, sails are in the water, winds are 70 knots, and you cannot cut it all loose for hours. You also need to be able to sail (and therefore heel) and start and stop the engine at will. Often you need both sails and the engine to cross bars, get off lee shores, etc.

[Terra Nova]

You'll want to lower the muffler so you can also lower the water-injected elbow. Then run the water-lift muffler's outlet line well above the discharge seacock before exiting. Looks like a poor location for the seacock, where you need to be constantly active trying to keep the engine from flooding with seawater.

[Reefmagnet]

I reckon you also need a swan neck or loop between the muffler and through hull to prevent water siphoning or otherwise being pushed into the muffler when on a heel or in rough seas. The problem with the through hull mounted valve idea is that 1) it is inconvenient to open and close it and 2) Sooner or later you'll forget to open it (or close it). The water muffler will need to have the capacity to handle the water left inside the loop at engine shut down, of course.

[cal_d_44]

georgelieber if the exhaust is high enough to clear the water when at max heal, when docked wont the exhaust exit onto the floating dock?

[GordMay]

See the exhaust tutorial ➥ http://www.northern-lights.com/PDFs/...t_drown_me.pdf

And ➥ Exhaust System Fundamentals ~ by Dave Gerr - Part 1 = 10 pages Part 2 = 12 pages Dave Gerr is director of the Westlawn Institute of Marine Technology, a practicing Yacht Designer, and noted author of: "The... Cruisers & Sailing Photo Gallery

And ➥ Yanmar Exhaust Diagram - Cruisers & Sailing Photo Gallery

[cal_d_44]

Thanks GordMay