sea water intake
My Dolphin 31 is raw water cooled, the inlet via the saildrive and a short pipe the the water pump. Because sometimes bags wrap around the saildrive causing a blockage, I have utilised an unused sea cock next to the saildrive and put a Y piece in so I can have either both open or one or the other, This has resulted in low water coming from the exhaust.Does anyone know if what I have do is a good or bad idea, or is there some reason why you cannot do this.
Sounds sensible enough to me, I've recently been following the build of an Odyssey yacht and they have installed 2 discreet sea-cock inlets either side of the keel for the engine saltwater intake - in attempt to avoid any potential blockage.
If you are finding reduced water output from the exhaust then that would suggest to me that perhaps there is air trapped in the hoses somewhere, could this be the case?
One question I would be asking myself; in what situation do you find you have reduced water output - with the 3-way valve taking input from the through-hull, the leg, or both at the same time?
I certainly can't think of any disadvantage to having that setup, apart from the common-sense approach of less holes in the hull below waterline = better, but in your case the hole is there anyway. Out of interest why is there such a thing as an "unused" sea-cock, as I find people have a tendency to avoid drilling holes for no reason?
In theory there is no reason why using a different intake should make any difference. You don't say whether the shortage occurs when you have one or other of the intakes in use. You need to ensure your seacock and Y valve is adequate diameter, typically 3/4" bore, but may be 1" dependent on engine. Also check your impeller and any signs of wear in the pump body.