Cockpit Sump Pumps

Repair or modification of Boston Whaler boats, their engines, trailers, and gear
jimh
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Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
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Cockpit Sump Pumps

Postby jimh » Fri May 11, 2018 11:08 am

A recent inquiry by email about cockpit sump pumps led me to revisit my now quite old article (c.1999) on that topic in the REFERENCE section. See

Cockpit Sump Pump
http://continuouswave.com/whaler/reference/bilgePump.html

The article is listed in the REFERENCE index under the SMALL BOAT ELECTRICAL heading. That choice reflects the article's content is mainly about electrical wiring and control of the pump more so than peculiarities of the pump and plumbing.

In classic era boats, Boston Whaler generally used a centrifugal pump (and usually a RULE-brand pump) with a rating of 1,000 to 1,500-GPH. In this particular application the centrifugal pump works well. These pumps have two distinct limitations, but in the usual cockpit sump, both are overcome:

--centrifugal pumps cannot lift any water to their inlet; the pump inlet must be immersed in the water it will be pumping; and

--centrifugal pumps generally have poor performance if there is any head (the distance from the pump outlet to the exhaust that the water has to be raised) on the pump output. The rated output is often given for the somewhat not-useful situation of a head of 0-feet.

In the classic-era Boston Whaler hull, the pumps are nestled into the cockpit sump as low as possible, immersing the input. The output hose only rises about a foot to the through-hull exhaust fitting, so there is very little head on the pump.

I have not kept up with any changes in model or ratings or ownership of RULE and its pumps. I assume they are still in business and make a pump similar to the original one Boston Whaler would have installed 20-years-ago (or longer) if they sold a boat with the sump pump option. If readers have any other recommended brands or models or sizes they have found from first-hand use to work well as the cockpit sump pump in a classic Boston Whaler, please join this discussion.

ASIDE: I know that many people, including Boston Whaler, will refer to these pumps as bilge pumps, but in my thinking a Boston Whaler Unibond hull does not have a bilge space: what would have been the bilge is filled with foam. These pumps are usually used in sumps or other drainage areas that are provided in the hull, but not in the bilge space under a strict definition.

An important aspect of installation of a pump with a float switch control system is described in my article under the heading "Location of Float Switch." In order to get a system that works properly, the float control switch has to be carefully located.

dtmackey
Posts: 760
Joined: Thu Sep 28, 2017 9:29 pm

Re: Cockpit Sump Pumps

Postby dtmackey » Mon May 14, 2018 10:31 pm

Good write up Jim.

I used a small Rule bilge pump (as called by Rule) in my old 13 Whaler for over 8 years and it worked great. It was the model that quickly powers on every 2 or so mins and if there's no water or resistance on the pump it shuts off in under a second. I found that it did not impact battery life as it drew so little for such a minimal amount of time and there was no float switch to break to jam with debris. I find that boats that pound over waves (original Whaler designs 11 - 17') take a toll on float switches. For boats requiring a water sensing switch, the Water Witch is a far superior design with no moving parts to break from wave impact or jam with debris.

The same pump is already installed in the 15' Whaler project and this time I'm also hooking up the manual switch in addition to the built in auto feature.

D-