Installing The Bilge Pump

By Lenny Rudow
Published: October/November 2013

Installing an automatic bilge pump may be a simple task, but it's also extremely important — this pump will keep your boat afloat, so make sure it goes in right!

Surprising but true: Most of us depend on rather cheap little pumps to keep our rather expensive boats from slipping beneath the waves. Fortunately, today's automatic bilge pumps are far more powerful and dependable than those of yesteryear. But they still go bad from time to time, and whether yours are in need of replacement or you simply want to add an extra pump or two for a security boost, you need to make absolutely sure this job goes right. Ready to get started? Good — roll up your sleeves, and let's get to work.

Before You Begin

One of the main reasons bilge pumps fail is because foreign objects either jam the pump, or lock the float switch into the "on" or "off" position. Bilge gunk, leaves, oily crud, and sand are guaranteed pump-killers, so before you even begin mounting a new bilge pump, provide it with a clean place to live. It's easiest to do this when the boat is blocked up on dry land, when you can thoroughly wash and rinse the bilge and allow the mounting area to dry. Choose a spot as close as possible to the bottom of the V in your hull and as far aft as practical, which has a secure mounting location like a shelf or a block laminated into the hull, for just this purpose.

Step I: Mount The Strainer Basket

We're going to assume you're starting from scratch, with a new strainer and pump. (When replacing a pump, you may be able to re-use a previously-mounted strainer basket if it's in good shape and you match the brand). Many modern pumps have integrated automatic switches; in these cases you won't have to mount a separate float switch, but some boaters prefer the easy access a separate switch provides.

Start by removing the strainer basket, which does double-duty as the pump's mount, from the bottom of the pump. Place it onto the spot you'll be mounting the pump, and use a pen to mark the location of the screw holes. Then remove the basket, and drill shallow pilot holes where you made the marks. Wipe away any gel coat or wood chips, and give each hole a copious serving of 3M 5200 Adhesive/sealant to be sure water doesn't intrude into the screw holes and cause damage over time. Place the strainer basket in position over the holes. Screw it down using the stainless-steel screws that came with the pump. If you're also mounting a separate flapper-style float switch be sure to orient it athwart ship, so surging water doesn't slam it into the up position when you accelerate — a common way they become stuck.

Now go home, and take the rest of the day off. The 5200 will take 24 hours to stiffen up (and several days more to completely cure) and you don't want to knock the strainer askew or stress it before the sticky goop dries, or you might end up with imperfect seals.

Illustration of parts of the bilge pump system

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Tech Support

Degree Of Difficulty:
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  • Heat source (for heat-shrink tubing)
  • Knife or box-cutter
  • Power drill and bit (sized to match the through-hull's diameter)
  • Screwdriver
  • Wire crimper/stripper

  • 3M 5200 Adhesive-sealant $15
  • Adhesive-lined heat-shrink tubing $5
  • Bilge pump w/auto switch $65 - $220
  • Butt connectors $3
  • SS cushioned-clamps $12 - $30/ea.
  • Hose $2 - $5 per foot
  • Stainless-steel hose-clamps $5
  • Through-hull discharge fitting $7 - $28
  • Tinned-copper wire (gauge to manufacturer spec., length TBD,) $20 (approx.)

Approximate Project Cost
 (based on West Marine prices)

Approximate Yard Time/Cost:
This job may require wiring and working in constrained areas inside the boat, as well as working outside the boat. Therefore, it can be either very simple or quite time-consuming. Depending on the nature of your boat it should take anywhere from three to 10 hours to complete the job. At an average general yard work rate of $75/per hour, the price of labor for this job could range from $225 to $750.


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