Valve on Lift Muffler.

[JDCAVE]

I’m considering putting valves on the lift mufflers on my main and Genny. What tricks are there to drill and tap fibreglass and what size and type of valve and fitting are recommended? Deadman’s handles would be ideal, but I’m thinking of using a locking lever on the valve that I might just tie strap in the closed position.

Thoughts?

Jim

 

[Lepke]

If your plan is to drain the muffler, You don't need a big valve. I use a 1/4" compressor drain valve. When the engine starts and the exhaust pressure rises, the valve automatically closes. When the pressure leaves, it opens. Another way is use a normally open solenoid valve that closes the drain when the key is on or generator is in the run mode.
Drill a pilot hole, maybe 1/8" then do the final hole, slowly and carefully. Tap the hole to match your valve thread.
For a strong permanent thread, drill an oversize hole, thread and epoxy in a stainless bushing. Bushing shown is 1/4 x 3/8, available on Amazon.

 

[DavidM]

I assume you are thinking about putting a valve in the lift muffler exhaust so you can close it to keep water from backing up. But you said drill and tap which implies a new connection, for what purpose? The fiberglass on a lift muffler isn't more than about 1/4" thick which won't make for a good threaded connection.

There may be an easier solution to keep water from backing up. On my Mainship 34T which had a lift muffler, there was an equalizing hose from the bottom of the lift muffler (many have such a connection) to a thruhull a little below the water line. This means that any back flow from the exhaust can't rise above the water line so it can never get into the engine. Your boat/engine/lift muffler geometry may or may not work with this scheme.

But if you want to do it any way I think I would use a 3 or 4" CPVC ball valve (not cheap) glued to the fiberglass nozzle and then to a short section of CPVC pipe before connecting to your exhaust hose. Fiberglass will not make a particularly good joint with CPVC but 5200 should work ok. CPVC is good to 200 F which should be within normal operating temps.

What is a deadman's valve handle?

David

 

[JDCAVE]

Yes David, I’m going to tread very carefully, for sure. I know some people have these installed, and I thought they were drilled and threaded, but quite frankly I don’t know for certain. And you don’t want something so large that it damages the muffler if it is knocked.

Lepke: your photo isn’t visible.

Jim

 

[Eagle Pursuit]

I see the photo in Lepke’s post.

 

[Keysdisease]

Garboard drain plug if for a drain. There is not typically enough wall thickness in fiberglass exhaust components to drill and tap enough thread for my peace of mind.

For a larger size a bronze floor flange looks the same as the garboard drain but is available in a variety of larger sizes. I would recommend only bronze for this application. (NO brass)

 

[Pete Meisinger]

To add to Lepke's answer. I would recommend using "Marine Tek" for the epoxy. That stuff hardens and holds like you would not believe.

pete

 

[psneeld]

From a megayacht type engineer....

"This is done all the time on large yacht mufflers. If thickness of the muffler wall is a concern all you have to do is buy a square foot sheet of 1/2 inch fiberglass and cut a "washer" type of doubler and epoxy it in place where you want the hole. That will provide plenty of strength and thickness for drilling and tapping."

 

[Lepke]

Lepke: your photo isn’t visible.

It's a standard jpg.


A big advantage of draining your muffler is greatly reduced back pressure when starting. Engines spin faster and start easier in cold weather. Muffler water is made up in seconds.

 

[JDCAVE]

Thanks people. There seem to be several options I could work with here.

Jim