Bilge Pumps from several makers fit this group. We tested a Shurflo Piranha 500, a pair of Attwood’s the V500 and V625, a Rule 500 model 25D, and a Whale SuperSub 500 model SS5012.
Rule and Shurflo all have vertically orientated motors and snap-on bases designed to mount on a horizontal surface. The Attwood pumps can be mounted either vertically or horizontally. Each base also acts as the screen for the pump inlet. Shurflo added features include a swivel base and a screw-in motor cartridge, the latter making debris removal easy.
 Rule 500, model 25D |
The Whale pump is fitted with a horizontally mounted motor giving it a lower profile. Its base is designed for either vertical or horizontal mounting while the motor can also be snapped out for easy debris removal.
All pumps in this group cost between $15 and $25, passed the dry run test, and possess a 3/4-inch outlet.
Thay all also were equipped with AWG 16 tinned copper wire. Attwood, Rule and Shurflo all have higher temperature and voltage rated insulation than the Whale.
Lead lengths run from 25 inches on the Whale, to 29 inches on the Rule, to a whopping 69 inches on the Shurflo. Attwood’s pair of pumps, the V500 and V625, both have leads 31 inches long. The Rule is available with 6-foot leads for aobut $2 more.
Weak Performance from the Attwood V625
 Attwood V625 Bilge Pump |
Ironically, the worst performer in our test was the pump with the highest advertised GPH rating, Attwood’s V625. It eeked out a miniscule 188 GPH at 12.2 volts and 251 GPH at 13.6 volts.
Attwood’s Marketing Director, John Boot, told us “The performance of our V625 pump is right on with what is stated in our catalog and on the back of the aftermarket packaging. When we were doing marketing research on this product, some of our customers that manufacture boats with shorter sideboards wanted a pump with higher out than our 500. Our response was the 625, which provides greater output at lower head heights.”
Our performance testing of other pumps in the group provided widely variable results even though most are marketed as 500 GPH pumps.
The best performing pumps in this bunch were the Whale and the Rule. Both pumped at 75% of their marketed GPH or more on all tests.
The Whale actually bested all others by hitting 99% of its rated GPH at 13.6 volts.
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Final Thoughts
We think the Rule 500, model 25D, bilge pump is tops in this group based on good performance and a long warranty combined with a good price. This pump is also available with 6-foot leads. We’d gladly pay the extra $2 if we needed the longer leads.