I have CMI switchable mufflers and I found that two of the cylinders are cracked. The cylinders are spring return but have two 1/8" ports for connecting them. I'm sure one goes to the pump but where does the other one go?

I can find spring return cylinders that have one port on the extend side to connect to the pump and the other side is a small hole exhausting from the cylinder without a threaded connection just to let the cylinder return when the pressure is released.

If the return port is just an open exhaust in the engine compartment I will replace the $100.00+ each cylinders from CMI with $20.00 each cylinders that I can get from a local supplier. I would only have one line going to the cylinder too.

The replacement cylinders are stainless steel and aluminum. I boat in fresh water so if any water gets inside they should be fine. I don't see why it wouldn't work.

Just keep the cylinder stroke the same and you should be fine.
You might want to put another 90 in the threaded exhaust port to keep any water spray out.

Thats what I'm having questions about. The cylinders that I can get only have one threaded port. The other one is only like a 3/32" hole for exhaust. If the CMI system works by pressure it will work. If they work by vacuum they will not.

Thanks

Roger,
You are right the other hole is the exhaust. If your cylinders are in the bilge then you wont have a problem. If they are outside then you will have to put a connector on and plumb into the boat to keep from getting water inside.

Put them on for 20 bucks I have seen a few boats with no vent line on I have replaced 3 out of 4 on my gaffreg mufflers at 100 a pop it gets old and they are vented inside.

Mark

My cylinders are outside. I cut the tubing that connects to the cylinders last Sunday and the cylinders had water in them. The mufflers have not worked on the boat since I bought it so who knows how and when it got in there.

The cylinders that I'm looking at are made for harsh wet environments. Sounds kind of like like the back end of a boat and at $20.00 each I'll give them a try.

fstboater, I don't mind paying a little extra for things but $100.00 for those cheap cylinders is a major ripoff.

I will have to make custom connectors to keep the spacing right but saving $320.00 makes it worth my time.

Thanks