MS 34T Muffler Cooling Pick-up

[boiler81]

New owner of 2009 MS34T with single Yanmar. I took delivery of the boat and piloted 6 hours to my home port without issue. Boat has been moored without starting engine since then pending replacement of engine raw water hose, which surveyor recommended replacement. While working in the engine room, I noticed a closed seacock with a hose running to the base of the muffler.
Neither the previous owner nor my surveyor made any mention of it and the Mainship manual is silent on this, but does identify it on a raw water diagram.

What is the purpose of this raw water "Muffler Cooling Pick-up" (behind SS support in photo) and did I damage my muffler/exhaust running with it closed?��

 

[Bacchus]

Brad
Congrats as a "new" MS owner.
Here's a thread that covers the specifics so no need to repeat it all.
Basically it is an "overflow" or "equalzation" line not a supply and should remain open to function.
https://www.trawlerforum.com/forums/showthread.php?t=21304

As an aside the MS Parts sticky in the Marlow MS section has some useful parts info. It can also be found on my Bacchus website, along with other useful info.
I did post a searchable BOM for the 34 T/HT that helps locate part pics & source info

 

[DavidM]

As noted by Don above and in the linked thread, it is an equalization line that protects the engine from water backing up from the muffler. The valve should be kept open for it to work.

Running with the valve closed isn’t a problem, but you lose the back up protection when the engine is shut down.

I think that the 34T has unique geometry that lets it work. You do not see it very often on other boats. FWIW, the Mainship Pilot 34 with the same engine doesn’t have an equalization line.

David

 

[PM]

Wet mufflers are self cooling. No additional cooling is needed. Wet mufflers do not get hot, barely even get warm. I am not familiar with the pressure equalzation aspect, no boat I ever owned was so equipped.

pete

 

[rgano]

As noted by Don above and in the linked thread, it is an equalization line that protects the engine from water backing up from the muffler. The valve should be kept open for it to work.

Running with the valve closed isn’t a problem, but you lose the back up protection when the engine is shut down.

I think that the 34T has unique geometry that lets it work. You do not see it very often on other boats. FWIW, the Mainship Pilot 34 with the same engine doesn’t have an equalization line.

David

MS Pilot 30 IIs do not have this equalization valve either.

 

[jgwinks]

My '73 Concorde 41 has something similar. A 1 1/2" hose tee'd into the raw water discharge before the mixing elbow. This runs to an above water through hull which is kept partially open. I'm told it's propose is to divert excess water from the system to relieve back pressure. A side benefit is it will bleed off any water backing up into the system and break any siphon. Downside is you have to close the seacocks before winterizing the engines and they're hard to get to. If you don't the AF never gets to the mufflers.

 

[boiler81]

Thanks for the replies and clarification of this "Muffler Cooling Pick-up" seacock.
The equalization for protection against back flooding engine makes sense, especially knowing MS history with this problem.
Seems odd, that they chose to call it a "cooling pick-up", but I will open it and leave it open.

Thanks

 

[Jeff F]

The equalization for protection against back flooding engine makes sense, especially knowing MS history with this problem.

Yep. Maybe by the time the 34T was introduced they had recognized the issue.

I'd like to have something similar on my boat.

 

[danderer]

Thanks for the replies and clarification of this "Muffler Cooling Pick-up" seacock.
The equalization for protection against back flooding engine makes sense, especially knowing MS history with this problem.

I know from personal experience that several 34Ts manufactured in the 2006 timeframe had problems with water entering through the generator exhaust. Don't know if they every changed/improved the design.

I'm not aware of any such problem on the main engine(s).