Thanks for the input. An unexpected thing about the eickert manifolds is that the collector on them is only 3.5" - so at the moment, as that's the collector outlet size, it runs 3.5" dry all the way to the tip with a 4" water jacket.
But I am thinking I'll go back to 4" ID tailpipes since that gives me more options for inserts to try (I have some 4" GGB inserts - but as above, they only moderate the crackle)
Looking at available options - does anyone have an opinion on the GIL Select Sound mufflers? Can they run dry and are they effective when dry? And Hardin are listing them - I wonder if they have stock?

Any info on these? I’m dry to the tip with stellings and it sounds spectacular however their ear busters big time. They were supposedly on 1150 hp sc engines with no power loss. ??? 4 1/2”.

Been along time , I had actually bought them from summit or jegs of all places and were 5", the ads today I see look like same stuff although price has went up substantially

That's interesting.
HPI is currently into Harley performance parts if it's the same guys. https://www.horsepowerinc.net/
Been around for 20 or so years.
Guess maybe they ventured into marine at one time. I was unaware if so.
Pair listed on Ebay.

Figured, i see the listing on summit and about to put an order in after your experience, cheers

did quick search Here are some used hpi 4”
https://www.ebay.com/itm/255892970417

Thought you guys might be interested in how this all turned out.

The end result was a pair of Gil Mufflers on almost completely dry tailpipes (Almost completely - because as it is, I have 3mm pisser in the bottom of each pipe - so that the headers drain down and to try and avoid burning up the mufflers)
In addition, I built water dumps from the tailpipes that splash over the mufflers too. All clamp on so I didn't need to cut too many holes in the transom or deck.



All works well and it's turned the noise level in the harbours & marinas from that aggressively loud dry pipe sound to very similar to a full wet setup. Not quite quiet, but not ear bursting any more. Here's a couple of short clips at both idle & fast idle:


While I was doing it all, I also added the biggest old old school EGR valve I could find to each of the headers immediately after the collector - so that when there's negative pressure in the tailpipe at idle, it sucks through this and reduces water being reverted - that also worked well and at idle, it's sucking a good amount of air in through the EGR valve rather than quite as much water back up the exhaust. I hope this means I can add a little more water to the tailpipe tip which should quieten it down a bit more again.

Show us your EGR setup?

Have also got a pair of EGR pumps if needed, but at the moment I don't think they're necessary.
I did question if they would do anything at all - but at idle/fast idle, there's an appreciable amount of airflow going in through them - anything that means I can dump in more water to the exhaust without reversion is good.
The other side of the flange has a lambda sensor in it - for the time being to help me refine the map, but also give options for closed loop cruising in future perhaps.

Oh, I see. You put some evac u pan check valves to bring fresh air into the exhaust.
What's the cylinder for?