What does the slotted version accomplish? Helping get the water out?

Also, these were so relatively inexpensive but effective that it seems too good to be true, lol. Has anybody heard of any downsides to these?

The slots are for exhausts that are dry to the end and have a tube inside the tails that dumps the water.

Ah, SB. And your previous post answered my question about performance. Thanks for the links!

I see where my 4.5" CMI dry tails need the 4" insert. The hard part is deciding on how long of insert and drilling the hole to hold them in.

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Hmmm, quite interesting that the 540 built by Ateco actually made more power with the GGB's.

My tips are the same as yours

Mine had a 3/16" hole on the bottom and with a pan head Phillips the hardware can't even be seen. The kits do come with 1/4" hex bolts but I put in the effort for a cleaner look. Are you just looking to knock a little bark off or have stiff sound limits?

The way they are constructed you can buy the longest ones and keep cutting off rings until you get the sound that you want. I thought I wanted the long ones but the 5.5" units are plenty for me.

So how do these inserts compare in sound level to something like the Corsa muffled tips that were used on a lot of boats, or perhaps the Teague switchable tips?

Any update if this fixed the issue ?

Had the boat out twice last weekend. I am 90% sure taking the mufflers off cured my problem. I will feel even more confident after this weekend. Not quite ready to leave the dock without an extra set of spark plugs on board though.