wet exhaust below waterline advice please

Engine replacement is progressing and my thoughts turn to the exhaust system.

bearing in mind the old MD21b died from taking seawater down a bore, I'm keen not to have a repeat.

Currently in the boat is a 75mm rubber exhaust. starting at the transom it exits 6" or so above W.L.
inside the boat the hose runs in a big loop almost up to deck level ( swan neck?) before running back down below the floorboards in aft cabin. (by now well below W.L ) there is a cylindrical stainless and rubber silencer box although this hardly has enough capacity to call it a water trap, before the exhaust runs further down hill towards the engine.

hardly a surprise that water ended up where it shouldn't and surely not an original installation from a well regarded manufacturer.

New engine is 2" diameter. So, as I understand it. I need a downhill run from the engine into a suitable waterlock. then the exhaust runs uphill toward the rear of the boat. at the transom it goes way up high to form a swan neck. The water lock needs to be able to hold the capacity of all the hose uphill of it calculated by pi r squared x length of hose.

Finally I need a syphon break above the waterline in my raw water input between inlet seacock and raw water pump.

Is this all correct? also, who makes an enormous waterlock because with a centre cockpit boat with a long exhaust run , at a first glance the vetus waterlocks aint gonna have the capacity.

anyone out there made their own water lock from Grp? was thinking it could then be made to fit shape of inside of hull?

grateful for all advice, experience , opinions.

I want to get it right from the outset.

Check now

Goto MIC to know more.

That sounds great -
You have dumps - I did the same think with mine but I run the water so that it sprays onto the sides of my drives.
Most of the dry exhaust I have seen have the water spraying off the end of the tails.

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