Diaphram Bilge Pump Installations ~ Complete May 2015

The diesel fuel tanks tanks were ready for re-installation, but prior to that was to determine why such rapid failure had occurred. With everything open we found 5 non-operable bilge pumps. They were all of the type that sit in the bilge in a semi submerged position. Tracing their wiring we found 3 in-line fuses that were hidden within wire bundles with blown fuses. Only 1 of the 5 pumps tested OK, but it had no 12V power.

Examining the boat, the original design intent was clear. The FWD and AFT bilges were very deep with the length between them which ran the length of the salon and under the engine, that was 3" - 4" higher than the bilge cavities. It was in this high section that we found 2 bilge pumps, whose failure had let bilge water rise to immerse the base of the aluminum diesel tanks leading to their premature failure. Additionally, the FWD and AFT head vanity sink and shower drains were feed directly to their respective bilges. The FWD head had a strainage unit to remove hair and skin debris, but as the unit was inaccessible for cleaning it blocked and simply overflowed without treatment into the bilge.

It was decided that all future bilge pump installation would be diaphragm type mounted at least 5" clear of the normal bilge water high level, and that the only thing in the bilge would be the float switches set to switch on at a 4" water height and off at about 3". The draw tubes to the pumps would be " hose without a strainer that could block. The tubes are at 1" from the bilge bottom to prevent drawing solids into the pump. The bilge pump power was routed through safety fuse hubs and was "always on". As both bilges are accessible for visual inspection and periodic test (weekly) and the bilges can be flushed as necessary. Use the BilgePumpPDF01 -> BilgePumpPDF04 links to view the pump and float switch data sheets.

At a later stage in the boats refit a question of how to handle Air Conditioner condensate water was addressed. It was decided to route both condensate drain line to a Y and then to the FWD bilge. In operation we have found that this condensate water keeps the FWD bilge water clean. The AFT bilge flow is almost solely from grey water. The prop shaft seal is a dripless mechanical seal that is leak free.