Johnson Pump 09-806B-1 F35 Impeller | MC97 Cooling

The Johnson Pump 09-806B-1 is the flexible impeller that keeps raw water moving through your F35 engine cooling pump. It's a small part with a big job. When it's healthy, cool water flows through the engine and everything runs at temperature. When it's worn or torn, flow drops, the engine heats up, and you're shut down until it's fixed. That's why this is one of the cheapest, most important spares to keep on the boat.

This impeller is molded from MC97/EPDM, a rubber compound built to handle the heat and constant flexing inside a cooling pump. It measures 1.58 inches on the outer diameter, 0.37 inches through the inner bore, and 3/4 inch thick. Those numbers matter. The thickness is matched to the F35 housing depth, so the vanes wipe the pump wall correctly and the impeller stays put instead of walking out over time. It's sold as a single impeller, sized to fit the Johnson F35 pump exactly.

Here's the thing about flexible impellers. They're a wear item, not a lifetime part. The rubber vanes bend against the pump cam thousands of times a minute, and they take a set, harden, and eventually crack. Johnson's own guidance is simple. Change the impeller every year. We'd add one more rule. Change it any time you already have the pump cover off for other service. You're right there, the gasket is disturbed, and a fresh impeller is cheap insurance against a hot-engine day.

The number one killer of these impellers is running dry. The vanes rely on water for lubrication and cooling, so even a few seconds of dry running can melt or shred them. Always make sure the seacock is open and the pump is primed before you start. If you've been on the hard or replaced a hose, prime the raw water side first. A dry impeller can be ruined before the engine even settles into idle.

Replacing one is a job most boaters can do at the dock. Close the seacock. Pull the pump cover plate and gasket. Note which way the vanes are curved, because the new impeller goes back in with the same set. Work the old impeller off the shaft, clean the housing, and check the cam and wear plate for grooves while you're in there. A little glycerin or dish soap on the new vanes helps it seat and gives you lubrication for that first dry moment at startup. Line up the bore, push it home, replace the gasket and cover, and open the seacock. Fire it up and confirm you've got a steady stream of cooling water before you leave the slip.

Because this impeller matches the F35 pump dimensionally, it seats and seals the way the factory part does. That's the reason we stock genuine Johnson impellers rather than generic clones. Aftermarket copies are often cut a hair thin, and a thin impeller can slip in the housing, lose its wipe against the wall, and pump poorly right out of the box. When the whole point of the part is a tight, correct fit, matching the original spec is what keeps your cooling flow honest.

Who's this for? Anyone running a Johnson F35 engine cooling pump who wants to stay ahead of the maintenance instead of chasing an overheat. Keep one in the spares box, change it at the start of every season, and swap it whenever you pull the pump for other work. It's a cheap problem if you plan for it and a ruined weekend if you don't. If you also need the pump's gaskets, O-rings, or wear plate, grab those separately, because this listing is the impeller by itself.