I am in the process of redoing all of the plumbing in my boat. The automatic bilge pump hose runs up to a vented loop behind the galley sink then down to a T in the sink drain line. In my forum reading it sounds like most people have straight shot out to the transom someplace. Was this arrangement typical for the '87? is there any real concern with this set up or should I add a new outlet someplace else well above the water line?
Justin : The normal bilge Pump exit for a 1987 C34 is a line out to the starboard side transom!!
My only hangup with your present arrangement might be the size of the hose the vented loop empties into. The normal sink drain hose to the production thru hull is 3/4 inch!! Maybe the PO installed a larger thru hull & hose??
Check the requirement of the hose size recommended for your bilge pump!
A few thoughts
Justin, your arrnagement means your galley sink drain seacock has to remain open all the time. The OEM Mark I bilge outlet thru hull was at the low center point of the transom. You might already have one there because that's where the manual pump in the port side of the cockpit runs to.
The Pump outlet is ¾" which runs through ¾" hose through the vented loop and down to the T. The sink drain is all 1" hose down to a ¾"thru hull. So the tightest spot is the vented loop.
I'll have to look a little harder and trace some hoses. All I recall on the transom is the exhaust and 2 scupper outlets underneath the overhand just above the boot stripe and I believe it is the manual bilge pump at the lowest point in the center of the actual transom.
Was the automatic T'd into the manual pump?
Quote from: justinsteele on February 24, 2025, 02:59:21 PM>>>>>>>>>>>>>>>>>>>>>
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All I recall on the transom is the exhaust and 2 scupper outlets underneath the overhand just above the boot stripe and I believe it is the manual bilge pump at the lowest point in the center of the actual transom.
Was the automatic T'd into the manual pump?
Yes and yes.
Justin,
In spite of the PO's "better idea" the factory chose a transom exit above the waterline as the most efficient way to move a lot of water as quickly as possible. Pushing it through the bottom of the boat probably not the best way to achieve that. I'd return it to the original configuration those guys at Catalina seem to know what they're doing.
QuoteIn spite of the PO's "better idea" the factory chose a transom exit above the waterline as the most efficient way to move a lot of water as quickly as possible. Pushing it through the bottom of the boat probably not the best way to achieve that. I'd return it to the original configuration those guys at Catalina seem to know what they're doing.
I agree. I don't have that much faith in anti-syphon valves. I can't remember ever seeing a bilge pump drain that wasn't above the water line.
Jim
I have to bilge pump "outlets" on my 1990 sugar scoop transom; one for manual pump and one for electric pump. Both get submerged at time depending on boat speed and sea state. Neither have check valves but both have an "anti-syphon" loop in the hose that routes it high above the waterline and is secured to bottom of the propane shelf in the aft locker. The high loop on the auto bilge pump was secured by a zip tie. Once the zip tie detached causing the hose to fall below the waterline—allowing seawater to back-feed into the bilge. Took me awhile to trace this issue. Fortunately, it was NOT a lot of water, but it could have been.
Justin : I believe that your manual bilge pump exit is in the center of the transom low.
If your boat ever had a factory electric bilge pump the normal factory exit is on the starboard side of the transom up about foot.
A few thoughts
Justin, when I first purchased my '87 the bilge pump hose was a "straight shot" to the outlet on the centre bottom of the transom. On my first sail (a 30 mile run from Melbourne to Geelong in 25 knots) I was running directly downwind for several hours, with waves coming up from behind and breaking onto the transom. The helm became fairly sluggish, so I decided to go below and see what was going on. There was water in the bilge, up to the floor-boards!
Then of course the bilge pump decided it wasn't going to cooperate and we had to manually bail all of that water with the largest saucepan in the galley. On realising the water was COMING IN THROUGH THE BILGE PUMP, I blocked the outlet (my boat has a very handy swim step, so reaching the bilge pump outlet was very easy), and the water stopped coming in.
So if you relocate re-plumb the outlet above the water-line on the transom, make sure that part of it rises above the outlet, not a "straight shot"...
Justin, I believe the original hose layout ran straight to the transom. The manual outlet is low on the transom centerline. The 1 1/8" electric bilge pump outlet is on the starboard side higher up near the chainplate. The 1 1/8" hose had a couple check valves in the hose. When I replumbed my bilge pump system to add a 2nd larger electric bilge pump, I removed the check valves from the 1 1/8" hose and added an anti siphon loop up by the galley sink.
You could just use a longer hose and put a loop of the hose coiled up high in the lazarette to act as your anti-syphon loop. My loop is fastened to the underside of the propane shelf.
Without check valves there's a lot less water run back with the loop at the galley sink.
Jon, I am confused. Less runback then what? If the loop is located above the transom through hull there should be less runback than if the loop is in the galley. Without leaving 12 ft of water in the hose. BTW—I believe my sugar scoop put my through hulls lower than your MKI so the syphon effect is pretty serious concern for me.
Run back from water pumped out of the bilge.
Jon, I am confused. Less runback then what? If the loop is located above the transom through hull there should be less runback than if the loop is in the galley. Without leaving 12 ft of water in the hose. BTW—I believe my sugar scoop put my through hulls lower than your MKI so the syphon effect is pretty serious concern for me.
I'm talking about water being pumped out of the bilge. If you're pumping water out of the bilge to the transom exit without check valves in the hose or a high loop by the bilge, all that water will flow back into the bilge when the float switch shuts the pump off. That may be enough water to cause the pump to cycle on and off.
Now I get it. Fortunately, any "runback" I get (after pumping) from water in the hose, is not enough to cause pump to cycle back on.