If you own an outboard engine, chances are sooner or later you'll demand a new h2o pump impeller. And the chances are also good that information technology'll come sooner—not later. Some manufacturers, like Yamaha, recommend that you audit the impeller every year and replace information technology every two to three seasons. To run into how this job gets washed by a pro, nosotros visited Norfolk Marine and had Yamaha Master Tech Chris Breeden take us through the process.

The first step in this process is removing the lower unit. Pull the bolts that secure it, and accept a friend help you slide the unit down and off of the outboard. Make sure you have a identify to sit the lower unit in an upright position, before you lot pull information technology off of the engine.

Next, remove the water pump housing bolts, and then lift off the housing. Use a flat-head screwdriver to help pop the housing free, if necessary. Now you can reach the parts you need to supplant: the bottom gasket, base-plate, impeller, central, and cup. If you lot're just doing an inspection, wait for a "prepare" (bending) in the impeller vanes, damage to them, or whatever melting or scoring on the cup. If any of these indications of vesture are present, supplant the parts.

With all the bad parts replaced, bolt the water pump housing back on. Then elevator the lower unit and slide the shaft dorsum up the outboard, giving the lower unit a little wiggle-jiggle until information technology slides into identify. Then, grease the lower unit bolts (so they don't seize in identify) and commodities the lower unit dorsum on.

Finally, give your handy-work a exam: hook a freshwater supply to the engine, start it up, and brand sure water is flowing through the outboard equally intended. Note—it will take a few minutes for water to piece of work its style through the powerhead and to the tell-tale, on large 4-stroke engines. Checking how the engine shifts is a practiced idea, besides, merely to make certain you lined everything up properly when re-assembling the engine.

More skilful outboard communication, from Primary Tech Chris Breeden and Boats.com:
- How to Change the Engine Oil on a 4-Stroke Outboard
- How to Change the Thermostat on an Outboard Engine
- 100 Hour Two-Stroke Outboard Engine Service
- How to Winterize a Four-Stroke Outboard
- Solve Your Outboard Motor Bug: Starting, Fuel, Shear-Pins
- How To Video: Salvaging and Pickling an Outboard
- How to Change the Lower Unit Oil on a Boat

Written past: Lenny Rudow

With over 2 decades of experience in marine journalism, Lenny Rudow has contributed to publications including YachtWorld, boats.com, Boating Magazine, Marlin Magazine, Boating World, Saltwater Sportsman, Texas Fish & Game, and many others. Lenny is a graduate of the Westlawn School of Yacht Pattern, and he has won numerous BWI and OWAA writing awards.