In our boat tests, we regularly criticise the lack of a manual bilge pump. Although most boats are equipped with electric pumps these days, what do you do if the power supply fails and you have a water ingress?
Manufacturers of small boats in particular then proudly show our testers their boats stowed in the back box,mobile piston pumps with the comment that they had met our test requirements. But is this really the case? What can small, mobile plastic pumps actually do in practice to prevent water ingress?
To get to the bottom of this question, we ordered six more or less similarMini bilge pumps at a large online mail order company. Why there? Because this is exactly where most skippers order such small accessories and therefore often do without advice or even a functional test in advance.
We tested the following models in detail: Docooler, MagiDeal, Sea to Summit, Osculati, Prijon and Whale. The prices were all between 15 euros and 40 euros.
The first surprise came when we unpacked the product. While most pumps (MagiDeal, Osculati, Prijon and Whale) came with drain hoses, the Sea to Summit and Docooler brands did not include this detail, which we thought was important. This is particularly annoying if you have to drain at a point in the boat that is not directly on the side.
In practice, pumps without a hose would be completely useless in small cabin cruisers, as you simply cannot get the water out of the boat.
If the deepest point of the bilge is at the stern, for example on inflatable boats, the bilge may still work. However, if the deepest point is further amidships, which is likely to be the case with almost all pleasure craft, it will be difficult to drain the bilge, and theTinkering with hose extensions begins.
The next point was thePump volume. Depending on the model, the capacity of our test candidates varied between a quarter of a litre (Docooler) and half a litre (Magideal and Osculati). You should not be blinded by the visual appearance of the pump.
A massive foam armouring can quickly give the impression of a large volume, but the cylinder diameter and stroke are actually decisive. And even cylinders that appear large on the outside are of little help if the stroke is only a meagre 25 cm.
Assuming sufficient fitness (50 strokes per minute), a maximum of around 25 litres per minute could be transported outboard with such pumps. However, if you take into account the force required to do this, you would have lifted around 50 x 1.6 kg (80 kg) per minute.
This brings us to the next part of the test:How difficult are mini bilge pumps to operate? The force to be applied depends on the volume, of course, but also on the design and mechanical properties of the pump. A large and well-designed pump does not necessarily have to be harder to operate than a mini pump with a stiff piston.
We measured the forces both when empty and when full. The differences were enormous. For example, the Sea-to-Summit pump, the Osculati and the Prijon pump only required around 16 N to move 0.4 litres of water. The Whale pump of the same size, on the other hand, required an impressive 46 N.
This may sound small at first, but in practice, once you've been pumping for half an hour, you realise that the difference of around three times the effort is not to be underestimated.
Anyone who has to use this type of pump for long periods of time must also rely on aGood handling dependent. The models from Docooler, Sea to Summit and Prijon stood out in particular.
They have a non-slip foam coating and are therefore easy to operate.
Another point is the valve located at the lower pump inlet. If it is unprotected, coarse impurities such as pebbles or pieces of wood are sucked into the pump and can block it.
However, we could only find suction grilles on the pumps from MagiDeal, Osculati, Pijon and Whale. All others rely on the user's prudence and a bilge that is as clean as possible.
If we summarise the individual observations, we come to the conclusion thatany pump is better than no pump. But: Pumps of this type are at best only suitable for the drainage of dinghies or bathing boats.
In fact, they are not a serious alternative to permanently installed bilge pumps.
From our test field theOsculati pump and the Prijon pump as test winners stand out. Although all the others also do their job, in practice they have shortcomings at one point or another.
You can find this article in the August 2018 issue of BOOTE. Available here.
