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Discussion Starter · #1 ·
I've been following MedSailor's recent travails with his engine (see: I hate boats thread) and one of the things that came up that may have caused his engine to fail was a clogged anti-syphon vent. So yesterday I went to my PSC 34 and looked for the raw water anti-syphon valve. I finally located it behind the engine control panel in a location that seems pretty difficult to access :(.

Has anyone found a good way to inspect that valve on a PSC 34? Is clogging a real issue with? It seems like a very inexpensive part that could cause a very expensive failure.... Most other anti-syphon valves on the boat are much easier to get to.
 

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Mondofromredondo
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I had the very same problem. I screwed around with that forever because I also wanted to test its antisiphon capability. I gave up and called a pro and magically he managed to put a brand new one in.

U definitly need far smaller hands than I have.
 

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I cannot get to my antisyphon valve through the little door to starboard of and below the companionway. I can just barely touch the valve, but that is all. I can get to it by removing what on most PSC34s is the engine instrument panel below the companionway (which on my boat has the wind speed and wind direction instrument displays). From there I can remove the screws holding the inverted U in place and pull it over to the opening to work on it.

I have a black plastic Forespar antisyphon valve at that high point in the raw water circuit. One other PSC 34 we looked at when we were boat shopping did not have the antisyphon valve, but instead had a tee at that point with a hose running to a bronze vent exactly like the fuel vent mounted in the cockpit. It dribbled water into the cockpit when the engine was running; that was the minus, the plus was there was no antisyhon valve to plug or leak.

Last year my antisyphon valve began to dribble, and it dribbled sea water over the front of the engine corroding it in spots. That may have been caused by my partially plugged exhaust elbow (now replaced) restricting the water exit and putting the raw water system under a higher than normal pressure. Anyway, two attempts to clean the valve have not been entirely successful. On my to-do list is to install the Forespar fitting that lets me connect a 1/4" rubber tube to the top of the inverted U in place of the antisyphon valve. Then inside the little door, I'll stick the end of the 1/4" rubber tube a couple of inches into a larger Tygon tube draining to the bilge. That will (1) prevent sea water from dripping on the engine, (2) remove the possibility of the antisyphon valve from plugging, (3) provide a syphon break and (4) let me check on the amount of water going into the bilge by opening the little door.

Forespar MF 846 Vent Barb Assembly

Bill Murdoch
1988 PSC 34
Irish Eyes
 

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Discussion Starter · #4 ·
I cannot get to my antisyphon valve through the little door to starboard of and below the companionway. I can just barely touch the valve, but that is all. I can get to it by removing what on most PSC34s is the engine instrument panel below the companionway (which on my boat has the wind speed and wind direction instrument displays). From there I can remove the screws holding the inverted U in place and pull it over to the opening to work on it.

I have a black plastic Forespar antisyphon valve at that high point in the raw water circuit. One other PSC 34 we looked at when we were boat shopping did not have the antisyphon valve, but instead had a tee at that point with a hose running to a bronze vent exactly like the fuel vent mounted in the cockpit. It dribbled water into the cockpit when the engine was running; that was the minus, the plus was there was no antisyhon valve to plug or leak.

Last year my antisyphon valve began to dribble, and it dribbled sea water over the front of the engine corroding it in spots. That may have been caused by my partially plugged exhaust elbow (now replaced) restricting the water exit and putting the raw water system under a higher than normal pressure. Anyway, two attempts to clean the valve have not been entirely successful. On my to-do list is to install the Forespar fitting that lets me connect a 1/4" rubber tube to the top of the inverted U in place of the antisyphon valve. Then inside the little door, I'll stick the end of the 1/4" rubber tube a couple of inches into a larger Tygon tube draining to the bilge. That will (1) prevent sea water from dripping on the engine, (2) remove the possibility of the antisyphon valve from plugging, (3) provide a syphon break and (4) let me check on the amount of water going into the bilge by opening the little door.

Forespar MF 846 Vent Barb Assembly

Bill Murdoch
1988 PSC 34
Irish Eyes
Bill,

I even removed the little door next to the companion way, but just barely managed to touch the valve. Not easily accessible, and I don't really want to remove the instrument panel on a regular basis as that has been caulked into place. I like your idea of replacing the anti-siphon valve with a tee and plumbing it to the bilge - that's an elegant solution.

Joost
 

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Closet Powerboater
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The t fitting instead of the valve is what i have and is what clogged. Mine clogged because it was exposed to the exterior of the boat where wssps could nest. If plumbed to tbe bilge this wont happen. The plus side of my install is that you can see it peeing water. I might reroute mine to pee above the cockpit drain. That way i can keep a close eye on it...

Medsailor

(Glad that others are learning from my misfortune)
 

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Discussion Starter · #6 ·
When I haul the boat for the winter, I usually tape up any exposed vents to prevent insects from getting in there. I feel for you, MedSailor, it's unfortunate that such a small insect caused so much damage, if that indeed turns out to be the cause.
 

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Closet Powerboater
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The t fitting instead of the valve is what i have and is what clogged. Mine clogged because it was exposed to the exterior of the boat where wssps could nest. If plumbed to tbe bilge this wont happen. The plus side of my install is that you can see it peeing water. I might reroute mine to pee above the cockpit drain. That way i can keep a close eye on it...

Medsailor

(Glad that others are learning from my misfortune)
http://www.sailnet.com/forums/2313778-post365.html (link to a single post)
This link above is a good reason why one should use caution when trying to re-engineer things. I hadn't thought about how re-routing the vent could mess things up.

Hopefully you Pacific Seacraft types don't have engines exhaust elbows that are below the waterline! Then, the only function of your vent loop is to keep the siphon from forming when your exhaust outlet through hull is underwater (unlikely).

MedSailor
 

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One of None
Hunter 34
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There is only one vacuum break I will use on engine systems and they are made by the Scot Pump Co.

You can buy it without the loop:


Or with the loop:
interesting.. even the bronze loop I have only has that little disc to stop the water from escaping But it's working well for about 5 yrs now. (knock on wood)
 

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On my to-do list is to install the Forespar fitting that lets me connect a 1/4" rubber tube to the top of the inverted U in place of the antisyphon valve. Then inside the little door, I'll stick the end of the 1/4" rubber tube a couple of inches into a larger Tygon tube draining to the bilge. That will (1) prevent sea water from dripping on the engine, (2) remove the possibility of the antisyphon valve from plugging, (3) provide a syphon break and (4) let me check on the amount of water going into the bilge by opening the little door.

Forespar MF 846 Vent Barb Assembly
I tried out my idea. There was not enough room above the inverted Forespar U to install the Forespar Vent Barb. The inverted U was too close to the underside of the companionway bridge. The spot was also full of wires.

Bill Murdoch
1988 PSC 34
Irish Eyes
 

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Pacific Seacraft 34
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One other PSC 34 we looked at when we were boat shopping did not have the antisyphon valve, but instead had a tee at that point with a hose running to a bronze vent exactly like the fuel vent mounted in the cockpit. It dribbled water into the cockpit when the engine was running; that was the minus, the plus was there was no antisyhon valve to plug or leak.
We have the arrangement aboard Jo Beth which Bill describes here. It's an annoyance to have dribbling water in the cockpit, but for us the pros have outweighed the cons. We've left it as is and live with it.
 

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I removed the plate in the cockpit under the comanionway where I have wind instruments mounted. For most boats that would be removing the Yanmar instrument panel. From there I could get to two screws; the first holding a cable tie around one hose and the second through a mounting ear on the Forespar inverted U. Through the little door inside the boat with an angle ratchet screwdriver, I was able to remove the third screw which held a cable tie on the other hose. With the three screws out I could move the whole mess over to the little door.

I was able to put the U back in place with a 1/4" NPT elbow and a 90 degree 1/4" hose barb installed in place of the Forespar duckbill vent. The elbow was oriented to starboard, and the barb was oriented down. I attached 8 or 10" of 1/4" rubber hose to the barb and put everything back together. I also ran a piece of 1/2" clear vinyl hose from the spot behind the little door to the bilge near the engine raw water intake valve. It followed the fuel tank vent hose, and I kept it in place with cable ties around the vent hose. With the rubber hose inserted in the vinyl hose and the engine running, a stream of water flows into the bilge. There was more water going to the bilge than I wanted, so I put a 0.5mm orifice in the end of the hose and reduced the stream at 2000 rpm from 1/4" diameter to squirt gun size. That was still to much, and I will replace the orifice with a plastic 1/4" tubing ball check valve when I next get down to the boat. That may be in January when we leave for the Bahamas. The valve will be at the end of the rubber hose where I can easily get to it for inspection and cleaning.

I also wire brushed, rinsed, and repainted the rusting spots on the engine where it had been corroded by salt water dripping from the valve.

Bill Murdoch
1988 PSC 34
Irish Eyes
 

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Discussion Starter · #16 ·
Hi Bill,

Thanks for the detailed description - that's very helpful. In my case, that panel has the engine instruments. I was hoping to avoid taking it out as it is caulked in place, but it looks like I have no other option - that vent hasn't been checked in eighteen years or so.

Joost
 
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