In this 3 part series I show how I installed bilge pumps in a Lagoon 38 catamaran.
In part 1 I show how I made brackets for mounting the pumps in the narrow keel sump.
In part 2 I show how I ran the hoses and installed the thru hulls.
In part 3 I show how I did the wiring.
Cap – regarding your very helpful bilge pump installation videos – you don’t mention having an upper loop (?) in the hose to keep water from flowing in, in a sinking situation. I’ve had very nasty replies on boating sites when I said I do not have that air lock. You mention that any loops will seriously impact pump efficiency. If I have a short hose run, should I create a large loop to prevent back low?
I generally recommend a small loop at the thru hull to prevent back flow from waves and such. I also like to install the thru hull as high above the waterline as practical. On a sailboat that would be the transom or hull side aft near the transom. On a power boats the transom also works well but to keep the run short the hull side often works better. If the thru hull is closer to the water line a loop would be needed to prevent back flow if the boat is heeled. In the case of a sailboat where the boat could remain heeled for a longer time a vented loop would be required to prevent back siphoning. No two installations are going to be the same so generally speaking you need to think about possible problems from heeling or listing and plan your installation to reduce the possibility of back flow. The compromise is you do not want to increase head pressure from lift higher than needed. Never rely on a check valve to prevent back flow into the boat. Hope that helps and do not worry about comments on the forums people on those tend to be a bit rude at times but you can usually pick out the ones that know what they are talking about from those that do not. Let me know if you have any other questions.
Thanks! That helps.