T-H Marine 800 GPH Automatic Bilge Pump, 3/4 in Hose

The T-H Marine 800 GPH Automatic Bilge Pump is the kind of pump you install once and mostly forget about, which is exactly what you want from bilge gear. It's a submersible pump with a built-in automatic float switch, so it watches the water level for you and kicks on when the bilge starts filling. No separate switch to wire, no float to mount in a tight corner. Drop it in, plumb it, wire it, and you've got automatic protection down low where water collects.

Rated at 800 gallons per hour on 13.6 volts DC, this one sits in the sweet spot for small to mid-size boats. Think 20 to 25 foot center consoles, bass boats, aluminum fishing rigs, and runabouts where you're clearing rainwater, spray, and the occasional bit of intrusion rather than fighting a serious breach. It draws about 5 amps while running, so it's easy on a small battery bank and won't drag your system down if it cycles a few times overnight at the dock.

The automatic switch is the heart of it. When water rises, the float trips and the motor starts. When the level drops back down, there's an 8 second shut-off delay before the pump stops, which keeps it from rapid-cycling every time a wake rocks the boat and sloshes the last bit of water around. That delay matters more than it sounds. A pump that clicks on and off a dozen times in choppy water wears out its switch fast and runs the battery down for no reason. The delay lets the bilge settle before the pump decides it's done.

Wiring is straightforward. The leads are tinned copper, so they resist the corrosion that eats plain copper alive in a damp bilge. That's a detail worth appreciating. Most bilge pump failures we see aren't the motor giving up, they're a green, crusty connection that finally quit passing current. Tinned wire buys you years. We still tell folks to seal every connection with adhesive-lined heat shrink and run a properly rated fuse, usually a 10 amp, on the positive lead close to the battery. The pump pulls 5 amps in normal use, but you want headroom for startup surge and a fuse that protects the wire, not just the motor.

It's ignition protected, which means the motor is built so it won't set off fuel vapors. That's the standard you want in any bilge or engine compartment where gas fumes can collect. Even so, use common sense on placement and keep the pump and its connections away from the battery and any fuel fittings when you can. The impeller shaft is stainless steel, so it stands up to saltwater far better than a plain plated shaft. If you run in salt, that stainless shaft is one less thing corroding on you season after season.

On the plumbing side, it fits standard 3/4 inch inner diameter hose. Run smooth-bore hose if you can and avoid tight bends, because 3/4 inch hose kinks easily on a sharp turn and a kinked line kills your flow rate. Double-clamp the connection at the pump and route the discharge up and out through a properly placed thru-hull above the waterline. A loop in the line helps keep water from siphoning back in through the discharge when the pump is off.

Real talk on what this pump is and isn't. It's an excellent primary pump for a small boat or a great secondary backup on a bigger one. It's not a substitute for finding and fixing a leak, and no 800 GPH pump is going to keep a holed hull afloat. Bilge pumps buy you time, not miracles. For most weekend anglers and cruisers running smaller boats, though, 800 GPH of automatic, ignition-protected pumping with a stainless shaft and tinned leads is exactly the right amount of pump.

Maintenance is easy and worth doing. Pull the pump base a couple times a season and clear out the leaves, sand, and debris that collect around the impeller, since that's what jams these up. Give the float switch a wipe so oil and grime don't gum up its travel, and test the whole thing by lifting the float or pouring a little water in the bilge before every big trip. Thirty seconds of testing at the dock beats finding out the hard way offshore.