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fastbreak 08-15-2013 08:26 PM

anti siphon valve universal m25
 
Hello, I am the proud owner of a Catalina 30 built in 1983 with a Universal M-25 diesel engine. For some time, I see water flowing from a pipe at the end of the anti-siphon valve conect to the heat exchanger. This occurs regardless of whether the engine is cold or hot. My question is why the water comes out of the pipe instead of going completely in exhauste. I dare not plug the hose that seems to serve as a vacuum. Thank you to enlighten me! p.s. sorry for my poor english but i'm leaving in Quebec city :):)

olson34 08-15-2013 10:10 PM

Re: anti siphon valve universal m25
 
Quote:

Originally Posted by fastbreak (Post 1074602)
Hello, I am the proud owner of a Catalina 30 built in 1983 with a Universal M-25 diesel engine. For some time, I see water flowing from a pipe at the end of the anti-siphon valve conect to the heat exchanger. This occurs regardless of whether the engine is cold or hot. My question is why the water comes out of the pipe instead of going completely in exhauste. I dare not plug the hose that seems to serve as a vacuum. Thank you to enlighten me! p.s. sorry for my poor english but i'm leaving in Quebec city :):)

Most of the Universal diesel installations I have seen, including our '88, have a small hose that goes from a fitting on the top side of the exhaust injection casting or just before that connection, and goes to a small thru-hull on the transom.
This "pees" out a small stream of water any time the engine is operating. This acts as a syphon break when the engine is shut down.

deniseO30 08-15-2013 10:23 PM

Re: anti siphon valve universal m25
 
seems to me its bad.. I had to replace mine. used a groco bronze inverted loop

JimsCAL 08-18-2013 08:45 AM

Re: anti siphon valve universal m25
 
Sounds like the hose to vent that water overboard is missing, or if there's a check valve there, its stuck open.

Stu Jackson 08-18-2013 12:04 PM

Re: anti siphon valve universal m25
 
There's no check valve in that line, shouldn't be.

The HX sends the heated hot raw water to the injection nipple on the exhaust riser to the muffler. This sounds like what you're talking about.

There is a vented loop on that line, before the nipple.

On our boat it is a Marelon loop with a small top fitting with the tiny little rubber flap. Made by Forespar, IIRC.

Ours is a 5/8" hose and vented loop.

Go to the Forespar website, or Google marelon vented loops, or use WM and you should be able to buy just the rubber ducky part to replace yours.

This is pretty simple. Good work on your part to notice it.

You may be interested in our Tech wiki which includes a lot of M25 engine info. www.c34ia.org, click on tech wiki, scroll down to engine.

fastbreak 08-20-2013 03:56 PM

Re: anti siphon valve universal m25
 
Thank you for the excellent information. I will change the rubber seal on the Marelon loop. The purchase price at Forespar is about $ 11 but lees transport costs are $ 30. Do you have a suggestion to reduce the cost of transport of this small joint. Thank you in advance! :)

katsailor 08-20-2013 04:08 PM

Re: anti siphon valve universal m25
 
Unscrew the fitting and clean the flapper before you buy a new one.

JimsCAL 08-21-2013 09:42 PM

Re: anti siphon valve universal m25
 
Quote:

Originally Posted by Stu Jackson (Post 1075615)
There's no check valve in that line, shouldn't be.

The flapper on the forespar marelon loop you go on to describe IS a check valve. Allows air in to when the engine is stopped but closes to prevent water exiting when running.

eherlihy 08-21-2013 11:08 PM

Re: anti siphon valve universal m25
 
Quote:

Originally Posted by katsailor (Post 1076809)
Unscrew the fitting and clean the flapper before you buy a new one.

+1

The M25 on my O'day, this hose has a ridiculously long tube, but it does not pee...

Clean the flapper, and the marelon housing, and you should be all set.

Stu Jackson 08-22-2013 01:37 PM

Re: anti siphon valve universal m25
 
Quote:

Originally Posted by JimsCAL (Post 1077545)
The flapper on the forespar marelon loop you go on to describe IS a check valve. Allows air in to when the engine is stopped but closes to prevent water exiting when running.



Jim, you're right in that it is an AIR check valve. Most people reading your post, me included, most likely thought you meant a check valve in the WATER line, which we agree does not and should not exist.


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