Replace water pump impeller Mercury 7.5 outboard motor - Outboard Impeller Replacement

Replace the water pump impeller in my Mercury 7.5 hp outboard motor. In this video I cover the replacement of my outboard engine impeller. Replacing the impeller in your outboard motor is important to prevent overheating and damage to the engine from a broken, damaged or hardened old impeller in the water pump that might prevent water from circulating in your outboard motor.
The Mercury 7.5 hp 2 stroke outboard motor that I am working on has been sitting for years, and the impeller for the water pump is very old and needs to be replaced before I run this engine for more than a few minutes.
Link to the kit for .438" shaft amzn.to/2Qmb0M6
Link to the kit for .456" shaft amzn.to/2P6HWYq
Link to buy zip ties! amzn.to/30YI8LP
As an Amazon Associate I earn a small commission from qualifying purchases.
Timestamps:
00:00 Introduction
01:20 Ordering the correct impeller replacement kit for your outboard engine
02:00 Removing the outboard lower unit
03:00 Tools needed and basic elements of outboard motor water pump system
03:35 Disassembly of the water pump housing for the Mercury 7.5 outboard motor
08:10 Opening up the new water pump impeller kit
09:30 Removing the old impeller
11:55 Inspecting the new impeller
13:10 Cleaning the drive shaft
15:20 Installing the new and correct size impeller
18:58 Reassembly of the impeller housing
#waterpumpimpeller #outboardwaterpump #mercury7.5impeller
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Sound effects and additional music is copyright free from iMovie

[@kellyjohnson4923]

Hey thanks Wayne. I have the same motor I just picked up and I'm NOT a handy guy. Appreciate the "real" work through and not glossing over the harder parts!

[@WayneTheBoatGuy]

Thanks! Take your time - try to be patient and pay attention to where and how everything comes apart and goes together.

[@marteng55]

You can use a 1/8" wide zip tie to align the impeller fins to make installation easier.

[@WayneTheBoatGuy]

Ooo so they make ‘fatter’ zip ties? That’s very good to know!

[@jmar2229]

@@WayneTheBoatGuy how about a hose clamp instead of a zip tie?

[@AnimalScienceTV]

Nice glass work table :)

[@WayneTheBoatGuy]

LOL - It was free... but it's not well suited for these projects!

[@kevinmccarey5015]

Hello again Wayne Great view on impeller repair. I am supposed to do one one my Alpha one / Gen 2 drive this spring. I watch several utube videos on the process. Wish me luck Be safe Be well

[@WayneTheBoatGuy]

My Volvo Penta has it on the crankshaft where the engine belts are - is that where Mercruiser Alpha One are located?

[@davidpatterson5728]

I looked at several videos and you are correct, didn't show it. I did find one that did, donyboy73. he also used the zip tie method. What I didn't see anywhere is removing the copper tubing. I had a piece of old impeller lodged in it. donyboy73 mentioned this as well. The bottom line, thank you for taking the time and others for doing these videos.

[@PapaMav]

I watch donboy73; great channel.

[@darrylmcleman6456]

Zip ties and stretch cords belong on a boat for sure.Handy for fishing and crabbing too.I know you are not in it to fish but the help to keep stuff in order.

[@WayneTheBoatGuy]

Yes sir they do!

[@1984framer]

Thank you for Showing us how to install the rubber part I was thinking I bought the wrong size impeller

[@caseyledford3662]

I have the exact same engine. Got it from my grandfather. That large O ring goes below the housing. The whole housing assembly including the water pickup tube lifts up and exposes the gearing case. O ring seals in oil and keeps water out. Mine was in perfect shape after 40 years, but check yours next time.

[@caseyledford3662]

There's also a bearing assembly just below the impeller housing

[@WayneTheBoatGuy]

That's good to know - thanks!!

[@marknolen9363]

The large O ring goes below the lower impeller housing. There is a screw on one side of lower housing if removed the lower impeller housing will remove with something you can pry up with. I have the exact same motor you do.

[@marknolen9363]

Also turn your motor upside down on a old rug or blanket to protect engine cover. You will find reinstalling the lower unit much much easier. It is so much easier to see what you are doing.

[@RyanSmith-mk3nm]

The big o ring is for the part that you put the impeller into, it comes out and there’s a bearing for the shaft in there

[@travisjohnson73]

Hello, so just an f.y.i. that around the 7:30 time stamp the impeller is spinning by the crank shaft, rotation of the motor and will always spin in that direction, when shifted into forward or reverse the impeller rotation is unchanged, the reverse and forward mechanical operations happen in the lower gear housing, thank you for reading and i hope this helps many others :)

[@WayneTheBoatGuy]

That's a good point!

[@picklz6917]

Ofc I ordered the wrong size the first time, just ordered the smaller one, hopefully I got it right this time

[@hermanmoody3241]

Put dish soap in base and on shaft twist clockwise until key aligns.

[@vvgfg5531]

Hi and thanks for such a great video. I have the EXACT same motor as yours, and have just gotten her up and running again thanks to your help. I am finding it impossible however to find parts for it as the serial number plate has fallen off. Which leads me to my question: What is the serial # on your motor?

[@WayneTheBoatGuy]

From about 1968 - 1972 these motors all looked similar. My S/N fell in this range 3016581-3274634 which made it a 1971.

[@vvgfg5531]

@@WayneTheBoatGuy cheers for that! Im in the process of getting more water through the tell tale. have changed impeller, but think the copper tube is not seating correctly inside the impeller housing. Im going to take it off again and try to fabricate a new gasket on the end on the copper tube. Its just a matter of trial and error.

[@robertsatoer4668]

wow man, really nice video. I’ve got myself a 7.7 hp mercury 1982 that i wanted to give some maintenance, your video really helps to see and know how your engine works in simple language. and because you did it for the first time, that obstacle is already taken by you for me. when the season is over ill replace my impeller and do some renewing on the fuel lines and sparkplug cables. I’ll let you know how it went!

[@WayneTheBoatGuy]

Thanks you! Just be sure to have a place to work and take your time and the more tools you have the better!

[@74nova36]

*So it’s seeming that the older carbon steel driveshafts are the .456” diameter and the newer ones made of stainless were the .438”*

[@PapaMav]

Impellers spine clockwise and the drive shaft does.

[@74nova36]

That bigger o ring goes around the water pump housing base piece. If you had the impeller out again you could slide the whole housing bottom over the driveshaft and there’s an o ring groove on the bottom of the plastic base.

[@josephbroten9188]

i have an impeller kit and it doesn't even supply that large o ring. Only two of them. WHen I took mine apart I didn't see any o rings nor any groove to put it in at the top of the shaft as he did.

[@74nova36]

@@josephbroten9188 that could check out. Sometimes it’s just a flush plastic fitment

[@michaelwinkelsas1580]

put the lube on the ends of the impeller fins or inside the cup

[@tshiesty5060]

I can’t get my impeller on the rod with the key on it

[@GarraiEoin]

7/16" & 11mm wrench size, are the same size. 9/16" & 14mm are also the same size.

[@pstrjoe]

I've been trying for 2 hours and the impeller is not even beginning to move... any advice? I'm frustrated!

[@WayneTheBoatGuy]

To remove it or install it? Try lubrication - I prefer dishwashing detergent.

[@pstrjoe]

I removed it. I tried to use a pentrating oil but it didn't work. I finally used a chisel to get it off. I'm convinced it was the wrong size forced on there. Thanks for your response

[@brianhocum9831]

Guy the easy way to get the water pump housing over the impeller is install the impeller and key then apply light downward pressure to the housing and at the same time rotate drive shaft in correct rotation direction and the housing will very easily slide down over the impeller. forget the zip ties

[@josephbroten9188]

yes, I did the same thing. Just start the rotation a little before so that when it drops in it will hit the key slot

[@josephcarr6832]

What if it doesn’t move with it

[@WayneTheBoatGuy]

That could be because it is the wrong impeller or it is not lined up correctly.

[@josephcarr6832]

@@WayneTheBoatGuy I just took it apart again and somehow the key moved when I seated it. Now I have to get the copper pipe back in the correct place. Any tips with that would be very helpful

[@kevinmccarey5015]

The Alpha one drive impeller is in the lower leg of drive the exact area where you did your out board motor impeller. I have to separate the drive 1/2 way pull it down and bingo there it is

[@WayneTheBoatGuy]

Good luck and try to maintain your patience.

[@alanrametta9867]

The easiest way to get the impeller out is with needle nose pliers

[@PapaMav]

Why not just cut the zip tie away, once you had it in place? When I've done mine, I soak the impeller with Armor All, get it slipperly, then get the fins started in the right direction, while turning the drive shaft by hand simulataneouly pushing the cover down over the impeller. This way all the vanes are in the right direction.

[@nightdrivers9138]

Hey man I got a 7.5hp mercury, I replaced the water pump housing, the impeller, and it still is not pumping water, everything is hooked up correctly I can prime it by pouring water from the top and it works for a second then stops, I also have exaust gasses coming out the the pee hole I'm frustrated as fuck.

[@staffanfogelberg6816]

Maybe some shit got stuck up in the powerhead. Try to blow through with compressed air.

[@nightdrivers9138]

@staffanfogelberg6816 I ended up having to pull the powerhead and there was some melted plastic between the powerhead and the copper tube, don't know where it came from but I just removed it and made a new gasket now she's pissing like a dream 🙂

[@staffanfogelberg6816]

@@nightdrivers9138That's what I thought. Very common. Probably small pieces from the impeller that traveled up there...

[@picklz6917]

Ofc I ordered the wrong size the first time, just ordered the smaller one, hopefully I got it right this time