Exhaust Guru's

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

 

It looks like a pretty standard setup. Use the smallest pipe and lift muffler possible. It doesn't need a siphon break since the water feed is on the downside pipe and much higher than the waterline.

 

Curious about the Gate Valve?

If you forget it and leave it closed or have to start the engine in a hurry...


risk/benefit analysis on that one as it feels there should be a better way - pressure in the exhaust could cause a hose to come off so ex/h2o going inside not out.

 

Skip the gate and just put a fairly tall loop on the outlet side of the muffler.

 

Cheers guys

 

All of the above, with a couple of more options.

If you mount the muffler as high as possible on the centerline it will give you better protection from backflooding, as more of the exhaust system will be higher than the waterline in a wider range of heel. The inlet could be at the bottom of the end cap instead on top as you have pictured, this would allow you to get the unit right against the overhead.

You could also make a two part system, with a more standard lift muffler on the deck where your muffler is now, and then lift water and gas together into a separator mounted as high as possible on the centerline. The separator would separate the gas and water and the water would discharge through a below the waterline through hull. The gas would discharge as normal out the transom. The nice thing about this is any water coming back into the separator will just drain back through the water drain, pretty bulletproof as far as water backflood.

 

Hang the engine start key on the exhaust sea cock, far quicker to open than a gate valve and less prone to failure.