Housing a bilge pump

[m_g]

Hi all,
Is it necessary for any part of a bilge pump (other than the shaft/prop) to be exposed to the water eg for cooling etc? I want to mount the back end into some PVC and just wondering if it is ok to completely cover it?
Many thanks
Mg

[thegadgetguy]

I would think they're probably fine as long as the shaft seal is wet. When they are used as actual bilge pumps, the upper portion isn't necessarily submerged anyway.

[jeff]

The pumps are designed to be run totaly submerged at times so are sealed. The only prob you may have is if run for a long time, the motor will get hot, if enclosed in a tube. On mine the maker advises not to run for more than 10 minuets without a 5 min break unless totaly submerged.This is as supplied... to encase them may lead to an overheat problem even though they are sumerged..

[fluxno]

filling the enclosure for the motor with oil will help with heat dissipation, if you in addition connect a soft hose to the enclosure(the hose also filled with oil), the seal on the shaft will see practically no differential pressure, and the motor enclose can ble very thin, because it wont see any pressure. the only important thing is to get ALL the air out, and if youre able: have a slight overpressure on the oil inside the container. 0.2-1Bar is probably sufficient.
this principle is called "pressure compensation" and is used with either a hose or a piston.