Johnson Pump F3B-19 12V Oil Change Pump, 5.5 GPM

If you've ever tried to change the oil on an inboard or a generator tucked down in the bilge, you know the drain plug is usually the last thing you can reach. That's the whole reason a pump like this exists. The Johnson Pump F3B-19 is a 12-volt electric oil change pump built to pull used oil straight up out of the crankcase, so you're not fighting a wrench in a puddle you can't see.

It runs on a flexible rubber impeller. That design self-primes, which matters when you're pulling thick oil up a long dipstick tube, and it moves a rated 5.5 gallons a minute once it catches prime. Both ports are 3/8-inch NPT, so you can thread on standard fittings and run a suction hose down into the sump and a discharge hose into your waste container. Power comes from the boat's 12-volt DC system, and this pump pulls around 15 amps under load, so it's happy running off a cranking battery for the few minutes an oil change takes.

The sealed lid is the part boaters appreciate most. It caps a waste pail so used oil goes where it belongs and not into the bilge or across the cabin sole. You drop the discharge into the container, snap the lid down, and pump without worrying about a slick. When the pail's full, the sealed lid keeps it contained on the ride back to the dock or the recycling drop.

Use it the way you'd use any oil extractor. Warm the engine first so the oil flows, feed the suction hose down the dipstick tube or onto the drain fitting, and let the pump do the work. It handles engine oil, gear oil, and lower-unit oil, and it's just as at home on a generator service as it is on the main engine. A quick word on what it isn't for: the rubber impeller isn't rated for fuel. Don't press it into service pumping diesel or gasoline. Rubber and fuel don't get along, and you'll ruin the impeller.

Why a flexible impeller instead of a diaphragm or gear pump for this job? Two reasons. It self-primes without any fuss, so you don't have to fill a line by hand to get it started, and it's gentle enough to handle warm, viscous oil without stalling. The trade-off is that it's a positive-displacement pump, so you never want to run it dry for long. A few seconds while it catches prime is fine. Leaving it running dry against a closed line will chew up the impeller. Keep the suction end in the oil and shut it off as soon as the crankcase runs dry.

Installation is straightforward, but a couple of habits will save you grief. Wrap the 3/8-inch NPT threads with Teflon tape and a little thread sealant so the ports don't weep oil under suction. Size the wiring for the 15-amp draw and put it on its own breaker or fuse. And when you're done for the season, run a little clean oil through it and store it dry. Flexible impellers last a long time when they're not left to sit gummed up.

At a rated 5.5 gallons a minute, most single-engine oil changes are over before you've finished wiping down the dipstick. Real-world flow on cold, heavy oil runs slower than the rating, so warm the engine first and you'll move oil noticeably faster. Either way, it beats a hand pump by a wide margin, and there's no cranking involved.

This is gear for anyone who does their own maintenance. Cruisers changing oil at anchor, anglers servicing a kicker or a generator, sailors keeping a diesel auxiliary on schedule. It's a Johnson Pump, so you're getting a name that's been building marine impeller pumps for decades. Wire it in once, keep it in the lazarette with your oil change kit, and you'll wonder how you ever did the job without it.