Johnson Pump 09-46840 Service Kit F35B-8/802/8007

If your Johnson Pump raw-water pump has started weeping at the shaft, or the flow feels weak at the helm, this is the kit that brings it back to life. The 09-46840 is the factory service kit for the F35B-8, F35B-802, F35B-8007 and F35B-8027 flexible impeller pumps. One box, every wear part you touch during a normal rebuild, so you're not chasing individual pieces across three catalogs the weekend you actually need them.

Here's what's inside. A genuine Johnson flexible impeller (09-808B-1), the mechanical shaft seal (09-0.2247.021), the end cover gasket, the O-ring (0.2173.440), and the end cover screw (0.0279.300). That's the full set of soft parts and fasteners that see wear on a normal service. The impeller vanes lose their spring over time, the seal starts to weep, and the gasket and O-ring harden and shrink. Replace them together and the pump pulls a strong, steady prime again.

This is the mechanical-seal version of the F35B service kit, and that distinction matters. Some F35B pumps were built with a lip-seal arrangement instead, and the parts don't cross over, so check what your pump runs before you order. If yours uses a mechanical seal, this is the right box. Not sure? Pull the end cover and look, or read the model stamp on the pump body and match it against the four series numbers above.

A raw-water pump is the heart of your engine's cooling, and a fresh kit is cheap insurance against an overheat. Most boaters we talk to rebuild theirs every couple of seasons, sooner if they run in brackish or silty water. Impeller life takes a real hit in salt and brackish conditions. A set of vanes that looked fine when you winterized can crack on the first hot afternoon in July. If you trailer between different bodies of water, or the boat's been sitting all winter, a pre-season rebuild is time well spent.

How do you know it's time? Watch for a weak or dropping water stream at the exhaust, a temperature gauge that climbs higher than it used to, or a wet spot under the pump from a seal that's started to weep. Pull the end cover and inspect the impeller. Cracked vane roots, a flat spot where it's taken a set, or missing tips all mean it's done. If you find rubber bits downstream, check and clear the cooling passages while you're in there.

A few notes from folks who've done plenty of these. Grease the O-ring lightly before it goes in. A dry O-ring is the number one cause of a first-season weep on these pumps. Go easy on the end cover screw, because the threads strip if you lean on them, so torque to spec or add a dab of blue thread locker and snug it evenly. When you drop the new impeller in, make sure the shaft key is seated and lined up before you close it up, or the impeller can bind on startup. And always replace the O-ring and gasket together. Reusing one while swapping the other is a classic way to pull air on the suction side and lose your prime.

One rule above all. Never run the pump dry, even for a few seconds. A flexible impeller relies on water for lubrication and cooling, and a dry run will shred the vanes before you've cleared the slip. This kit covers the standard wear items on a service. If the shaft bearing feels rough or notchy when you spin it, that's a bigger job than a wear-parts refresh, so plan accordingly.

This is a genuine Johnson Pump kit, not a mixed bag of aftermarket pieces. Buy it once, do the job right, and keep a spare aboard. When the pump finally tells you it's time, usually on a Saturday, miles from the ramp, you'll be glad it's in the ditch bag instead of on a shelf back home.