Exhaust elbow gasket differences

[moconnor]

As part of my spring commissioning, I pulled the elbows to check their condition, looks like to starboard side were replaced in the recently.
The port shows some pitting, so they are going to get new ones before splash day.
The gaskets I ordered have 4 rectangle water passages but the new ones I removed from the starboard had 2 rectangles at 12 and 6 with small round holes at the 9 and 3 locations.
I had no overheating with either side and no water intrusion yet.
These are wet elbows, someone please educate me on these two different styles of gaskets, is one better that the other?

[mmwjr]

From what I recall the new gasket is the one with two full passages open and two small holes. I believe these came out to proved better operating temperature. You could call Mercruiser help to get the answer directly from them.

[jparsons121]

Merc made a number of different gaskets based upon the "type" of exhaust. I'm referring to wet joint here. Not dry joint. See the following.

https://www.perfprotech.com/blog/art...e-exhaust-tips

Seems like someone mixed and matched.

John

[mmwjr]

Originally Posted by jparsons121

Merc made a number of different gaskets based upon the "type" of exhaust. I'm referring to wet joint here. Not dry joint. See the following.

https://www.perfprotech.com/blog/art...e-exhaust-tips

Seems like someone mixed and matched.

John

Good read, thanks

One thing I noticed is the flow diagram for cold flow shows the warm flow gaskets.

[moconnor]

seems like these all address raw water systems, I have a closed system and the parts drawing I've found show the restrictive gasket at the manifold/riser joint and the full flow gasket at the spacer/elbow joint. That's just the opposite of what I found when I disassembled the starboard side.

[mmwjr]

Originally Posted by moconnor

seems like these all address raw water systems, I have a closed system and the parts drawing I've found show the restrictive gasket at the manifold/riser joint and the full flow gasket at the spacer/elbow joint. That's just the opposite of what I found when I disassembled the starboard side.

I have seen them plumbed either way with the block off gasket either at the manifold to spacer joint or spacer to elbow joint. I don’t think there is a wrong way between the two it just needs to match up with how the coolant return hose is attached and the raw water hose. In the first case I mentioned the return hose would come off the top of the manifold and the raw water hose connecting to the spacer while the second case the coolant return would be on the spacer and the raw water hose on the elbow.