How To Change an Outboard Engine Water Pump Impeller

RELATED VIDEOS & PLAYLISTS:

If you own an outboard engine, chances are sooner or later you'll need a new water pump impeller. And the chances are also good that it'll come sooner—not later. Some manufacturers, like Yamaha, recommend that you inspect the impeller every year and replace it every two to three seasons. To see how this job gets done by a pro, we visited Norfolk Marine and had Yamaha Master Tech Chris Breeden take us through the process.

Caption: Watch and learn, as Yamaha Master Tech Chris Breeden, Service Manager at Norfolk Marine, changes a water pump impeller.

The first step in this process is removing the lower unit. Pull the bolts that secure it, and have a friend help you slide the unit down and off of the outboard. Make sure you have a place to sit the lower unit in an upright position, before you pull it 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 replace: the bottom gasket, base-plate, impeller, key, and cup. If you're just doing an inspection, look for a "set" (bending) in the impeller vanes, damage to them, or any melting or scoring on the cup. If any of these indications of wear are present, replace the parts.

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

Finally, give your handy-work a test: hook a freshwater supply to the engine, start it up, and make sure water is flowing through the outboard as intended. Note—it will take a few minutes for water to work its way through the powerhead and to the tell-tale, on large four-stroke engines. Checking how the engine shifts is a good idea, too, just to make sure you lined everything up properly when re-assembling the engine.

[boatsdotcom]

Hey Patti - assuming you did the impeller change properly, this means you have a clog somewhere in the system. Take a piece of 50 or 60 pound-test monofilament fishing line, insert it into the tell-tale (weep) hole, and spin it as you push to work it farther and farther in. You should be able to get several feet of line into the engine, and break the clog. If this doesn't do the trick, you can also take an air compressor and try blowing the clog out. Good luck!

[CrownOfThornss]

Thanks! Very clearly and thoroughly explained, and that in under 3 min!

[johnm]

Great video. It looks so easy and if you do check or replace the water pump impeller every year it usually is but if you wait 4, 5, 6 years the water pump will probably still work (depending on engine hours) but when you do try to take it apart is where the real problems start. I bought a used engine and I knew it had not been done in many years. It took a few drill bits a few heli-coils and way more time than I wanted. Keep it easy do this every fall when you pull your boat for the season. Lithium grease is your friend.

[fkarau]

Just bought an 06 Yamaha 9.9 and the leg was an absolute bear to get off. If nothing else just dropping the leg and greasing up the bolts every two seasons is a must. The impeller came out hard and formed into a spiral. Probably had never been replaced. There is so much riding on that $30 piece of rubber it is hard to believe people wait until it fails and causes overheating and a major engine failure before they even consider replacing it. This is the one thing I always replace with OEM parts.

[Redrockat]

Awesome video and very informative for checking the impeller thank you

[lysleanderson]

You missed the most important parts of the impeller change- how to remove and replace the plastic spacer, stainless collar and washers that hold the impeller on the shaft. Useless as a how-to video.

[blaster-zyxx]

Thanks for showing the parts I already know how to do and leaving out the parts I don't.

[johnboyte]

Flush port hose at top of motor is for FLUSHING only. Muffs need to be used when running the engine with boat out of the water.

[yooperluke]

Where is the portion of the video that shows disconnecting the shift linkage? Kinda have to do that to get the bottom off!

[glennzammit]

Where does the damper gasket fit?? It a black gasket and was with my impeller kit.

[pattihery]

Hello, I have a 50 horse johnson, and I changed the impeller, and I can't get the water to come out of the weep hole, heeelp!!!!TY ahead, Pete

[joracer]

I can see that impeller is in good shape, I can also tell the last time it was changed it was installed wrong, I can see the vanes are set 2 different ways....

[thesouthfloridafishingshow]

I am attempting to do the service on a 1993 250 Yamaha and the lower unit seem stuck. It doesn't want to let go the top. What can you tell me?

[kyleschlater]

some mercury motors have to be in forward gear does a 50hp 1989 Yamaha pro v have to be put in forward to replace the impeller? I'm Karen in MO

[rbathorn]

Glossed over realigning the shaft splines and shifter linkage. Showed the easiest steps in the process. No useful information.

[joeladams]

What is the stainless steel shaft with threads on top?

[andrickmarceloesparza]

I have a 2006 Tahoe q7i with a 5.0 Mercury with a failing impeller what do I do ??

[palms]

hello, i was given a 3 hp evinrude 1990 year, it was seized up so i proceeded to put penetrating oil in cylinders to break free, after about 1 week it broke free however it feels like its hitting inside after about 1/2 revolution going both ways. i tried to remove lower unit and cannot get it apart can you help. thanks 

[joemag]

Some guys think it is OK to start their engine with no cooling water provided and just shut it off when the gauge indicates the engine has reached normal operating temp. But doesn't water pump impeller damage occur quickly without cooling water ?

[Th-fcnq]

If my small mercury 110 9.8 hp only pumps water when its in forward gear what could be wrong with it. It will not pump water in neutral or reverse. Help?