How To Replace Mercury Outboard Water Pump Impeller

How to service and replace your water pump impeller on a mercury outboard. 75hp, 90hp, 115hp, 125hp.
Larger Optimax outboards run the same water pump, as do Mercriuser alpha sterndrives.

[@kennycook-uy8hv]

Great video, thank for the attention to detail!! Most others don’t even bother with the pertinent info!! Thank you

[@tuber5129]

I'm going to comment here so that another "home mechanic" researching this topic doesn't have to go through the pain that I did. First of all, thanks for making this video. I watched several videos before trying my impeller change for the first time. So long story short, nowhere in the the service manual or owner's manual does it say to drain the engine oil before dropping the lower unit. To my surprise, I had a flood of engine oil pouring out when I removed the shaft and dropped the gear box. I tried to research the problem on line and found a few people who had the same problem, but what they were being told was they had a costly engine oil leak and would need major repairs. This just didn't sound right to me, because I could see a hole at the top of the opening where the drive shaft stops, so I started to do more research. I won't go into detail, but the bottom line is that at least on my 2013 115EFI Four Stroke, you need to drain the engine oil before removing the gear case. I confirmed this with three different Mercury certified mechanics and called Mercury customer service.

[@elaineatkinson223]

Wow! AMAZING video with all the info I really needed. Well done mate, well done. Saved me so much time and mistakes I would have made with just my book.

[@ozskipper]

Omg... An internet mechanic that doesnt wear gloves... I salute you sir!! Youre a real mechanic.

[@TrybalRage]

Great video, thank you very much even all these years later. A couple notes - one, you can't really see the orientation of the face seal you put on top of the waterpump housing, I had to look that up elsewhere. My kit came with the seal and an install tool. The seal goes with the wide thin flange down against the top of the housing - the tool keeps you from pushing it inside and helps seat it nicely. Two - the bottom gasket on my kit was a thin metal one, and according to the papers that came with it replaces the large fabric gasket. Must be a new version or something. Finally, the rubber seal that you see at the end of your video on top of the housing water jacket did not drop out when I removed my lower unit. I ended up just greasing it a little in place, since the kit did not come with a replacement and I didn't want to risk trashing it. Thanks again! I don't know what people would do without tutorials like this one on youtube.

[@daleharding1339]

Dad (90 yrs old) wanted fishing trip with his two sons.I fly to SLC UT. Brother picked me up at airport, drove to dads, picked up him and his boat and headed to Flaming George. Got boat down to dock and thats when things started to unravel. 1. Batt dead - jump cost us $10.... then learned it's been one year since boat was in the water !! 2. Five minutes into lap close to marina to make sure engine can burn older gas mixed with stabilizer plus five gal new - a warning alarm came on - ZERO water pressure on gauge - no cooling water coming out of port. Marina tech stated impeller problem (dad has never changed it in 9 years ownership). One week to get part. at $145 - Two weeks to work it into schedule at $125 labor. Ok - back to brothers house - trip over. On a whim thought about youtube... Watched your video.. then found impeller kit online on Amazon - $38 + $4 overnight delivery! Watched video again - I can do this! Had it apart in 20 minutes... 5 being used finding a 15mm socket in brothers very limited tool assortment. Thanks so much for your help saving a father/sons 4 day fishing trip!!

[@OutboardAdvice]

Thanks for the feedback Dale, Glad I could help! :)

[@duro845]

That trip was setup for disaster from the jump. Hope you guys had fun anyway

[@strengthcourage9149]

Awesome video. Thanks for work putting it together!

[@webturbo]

What a great tutorial. I've watched several on here and this one is by far the best presentation .. I like the fact that you didn't get overly technical, but kept it easy for the everyday "shade tree mechanic" to understand. I will be changing the impeller on my 75hp Merc in about 2 weeks and will have my laptop on the workbench for reference with this video cued up!! Thanks again!

[@iwaotakai2915]

Man I've seen quiet a few videos and tutorials but none of them made sense to me. You had the best tutorial and very easy to understand. Cheers bro

[@billyarredondo]

Thank you for this video. I contacted several local mechanics to get this done but all said it would be a 3-4 week turnaround. I picked up the parts myself and it only took me about an hour and saved me all the labor cost. Awesome!

[@fredfurrer1035]

Looks like I can remove the gear box without taking the boat out of the water. Normally, I would be afraid of doing any work over water.

[@kenthomson4627]

Really good explanation and excellent tip about the direction of the drive shaft so the key can be easily aligned with the impeller. Thank you

[@chriswenberg4823]

Thanks for this tutorial. I have used this many times.

[@Nass1986]

I watched a lot of videos and no body demonstrate the way u have done it regarding in impeller replacement its a bit confusing u made it simple thanks

[@markramquist5276]

Ty dude they wanted 800 to change I did for 75 but I was looking on top of motor were water comes out your video is gonna make make owners of companies mad cuz it was easy once shown Ty again

[@trentpierce7656]

Thank you for this! I have a 1998 Force 90hp and could not find a video. This engine lower unit is identical to mine. Thank you so much! Worked like a charm.

[@Askeyb2011]

Great video. Some years ago I had an old 1971 2-Stroke 7 1/2 HP Mercury Outboard. I changed the water pump impeller several times. Kept going out. I then changed the whole housing everything thinking something was wrong because it kept eating impellers. I think it lasted longer after replacing all of it. Boat we have now has two Mercury 4-Strokes and have never had water pump go out. Replace the impellers every three years.

[@campy9sp]

Thank you for posting this video! Going to try my hand at helping a mate get a 115 pumping water again. You saved me quite a bit of time by describing the impeller renewal process brilliantly.

[@levicave4473]

Great video. I’ll be doing mine this weekend. I just got a 2001 125 Mercury.

[@fishman677]

Thanks for taking the time to make your video! I own a 1987 Mercury Mariner 75HP and have hesitated to replace the water pump myself. Thanks to you I will be doing it in a few weeks. You took the mystery out if it and made it clear and simple to understand. Keep on making videos! Thank you.

[@TheGMlover1]

Nice video thanks someone finally shows disassembly and reassembly with some advice to this video was very helpful

[@OutboardAdvice]

Thanks for the comment

[@twincitiesdashcam9119]

Awesome- I have a 2011 115HP Mercury and this video is extremely helpful- thanks for posting.

[@antoniomaceo4706]

Fantastic step by step instruction, easy to follow with no missing information. Thank you!

[@bodybuilderschickensnortht6121]

Hi Geoff, i just subscribed to your channel. I have to change mine on my mercury 90 HP outboard motor this week. This was the best detailed video i found so far. Thanks for helping us boaters out. Now i know how to handle. I am use to working on my LT1 trans am.

[@olebiker]

You saved me a lot of money by making this video. Thank you for going to the trouble to do it.

[@Broadside175]

Well done!, I'll be doing that to my 125 this week. Kudos for going the extra mile and greasing everything for the next time!

[@rolodarknet]

Very good thanks! I watched this and it gave me the confidence to clear the sand and shells out of my impeller rather than taking it into the shop. Used a water blaster through the top hole of impeller rather than disassembling it and a few 5mm x 5mm shells popped out! Impeller now pumping water as usual. Many thanks.

[@SupaNami]

one of the best IF not the best vid's on changing a water pump ... Great Vid Mate from the US!!

[@louissparks2496]

Good show. This is one of more complete and informative ones that I have seen.

[@kromprify]

Great video. You covered all the points in a clear manner and your video was concise and very useful. Thank You!

[@raybullard1927]

Well done, Geoff, awesome demonstration, many thanks

[@robguilfoil2470]

Excellent explanation of the procedure and tips to make the installation go smoothly.

[@wandasmith5178]

Great video. I just changed the water pump impeller on my Optimax 115. The only difference was that mine is a long shaft and the gear shift selector rod is longer. Great advice to put the motor in forward gear as it makes it easier on the install.

[@eldorado96]

Great video - very helpful to understand the relative simplicity of this job. Only one nit to pick (sorry!): You commented a couple of times on "keyway", but were referring to the key itself. The keyway is only the slot in which the key installs. Other than that, we get what you meant. Thanks for posting this!

[@cobravenomX1]

i put a piece of wire into the water hole it worked there was a bug in there. thanks you saved me a bunch of headaches. and repairs.

[@drcristiaan]

This video tutorial is brilliant ! Clear, educational, useful... Got me on my way. Thanks mate!

[@jasonspence3222]

Well done, great video, very professional and easy to follow.

[@anaranjado08]

Thank you for posting. With your help I just replaced the impeller on my Mercury 90hp 2 stroke.

[@shaunjones3119]

Well made video. Good job, thank you so kindly and keep up the great attitude! Cheers

[@jasonbennett556]

Finally someone that shows it how it is. Awesome video bud. Thanks.

[@daysleeperdoc1]

Excellent video! My force 120HP is exactly the aame as the featured Merc. Outstanding detail.

[@Mazomedia]

This is a GREAT video! Not just for boats but overall this lays to shame alot of other instructional videos. Well thought out. Good tips. Showing everything being done. NICE WORK!!1

[@tearbear8439]

Awesome Video. Not as hard as I thought it might be. Thanks.

[@fredzivicky6266]

Great video. You covered everything that needs to be and how to do it. Very complete and I’m glad I found this one compared to some of the other ones. . Thx again..

[@brents1541]

This video helped me out a lot today! I replaced the water pump and changed my lower gear oil in about an hour. This video was spot on. I have a 1996 force 120 by Mercury. Saved me lots of money. Thanks a lot!

[@bbreede1]

This may be a dumb question, but did you drain the lower gear oil first, then work on the water pump, then refill after reinstalling? I'm about to do the same on a 96 90hp force.

[@brents1541]

@@bbreede1 I did the water pump first, then changed the lower gear oil once everything was back together. However, it shouldn't matter how you do it. It was a pretty easy job honestly. Good luck.

[@Deaddancer69]

Great video...plan to replace the water pump on my '72 Merc 115hp. The one I burned out by forgetting to turn the hose on last weekend when I was driveway starting it. D'OH!

[@larryhart4880]

Excellent how to video . I hope mine goes just as easy as yours . Really like the step by step instructions. Thank ya for the little tid bits of info to . Didn't know it was that easy. Now I'm all jacked up to do mine . Thanks again for a awesome video. 😊

[@rustbox70]

I can't thank you enough! This video saved our vacation and countless dollars in repairs.

[@waynedevenny2599]

very well explained, good video footage and some smart tips. Thanks Geoff

[@filipinainthelandofmilkand9205]

Thanks. This video is well done and should make my impeller change much easier with no guess work. Great video!

[@OutboardAdvice]

@ober51 Thanks for the feedback! You will probably find it is exactly the same water pump. If it has the quickfoot gearbox I think. So if you follow the video you should be great! The only thing I have noticed from comments is the gearshift. Before putting the gearbox back onto the motor, rotate the prop shaft and confirm that it is still in neutral and you havent accidentally turned the shift shaft. Good luck!

[@davemacdonald892]

This was great. Thanks Geoff.

[@steverichmond9993]

Thanks for making this video! It helped me change my water pump for the first time. Great job!

[@macmac369]

Terrific instructor. U must be a professional marine mechanic.

[@texted1438]

Good video - I always put the motor in forward gear before dropping the lower unit and make sure the lower unit is fully in forward when reinstalling unit. It is possible for the shifting gear to be moved to neutral or reverse. If you reinstall the lower unit with the lower unit in a different location that the powerhead, the unit can start in gear.

[@alijabos]

I was looking for information on this. He doesn't mention it in the video. It is necessary to be in forward though?

[@freddombski]

I agree. One of the best videos on this subject. Makes me want to get out there and do my Merc. 9.8 which has been sitting for quite a while. Wasn't really using it anyway but I'll find a purpose.

[@danielbukacek6516]

Best video i've seen on changing a water pump. very useful/competent

[@Erated78]

Great vid, well done and nicely explained. I recently learned that Honda 40hp OB flywheel/shaft turns counter clockwise where upon we also discovered that someone incorrectly installed the impeller meaning the impeller splines "scooped" not "swept" the water. Not sure if you know what I mean. I plan to replace the impeller on my 2004 125hp merc shortly so thanks for this video. Cheers

[@raymondgroves3173]

Thanks for your information. I have seen factory produced videos that were no this good.

[@pamevans3587]

Great video! My husband really needed this.

[@paullightfoot6020]

FANTASTIC TUTORIAL THANK YOU

[@Nifetco]

Great advising Video and great performance. Thanks from Greece.

[@OutboardAdvice]

@radoslavrigas Hi, yes some kits come with the black tube. Depends what kit you get. When you remove the gearbox the tube can stick onto the water tube. You simply reach up and pull it out then fit it into the water pump. It is there as a guide for when you install the gearbox to get the water tube to slide into the water pump housing.

[@carlosdosreis5196]

GREAT VIDEO!!!! Thanks for the detailed explanation and tips.

[@biganos4780]

Thank you for posting this video! Merci pour cette vidéo très didactique.

[@anthonygodfrey6131]

Thank you for a very informative, and well explained video.

[@wirednomore]

Thanks for taking the time. Very helpful

[@spthurston]

Thank you so much for the feedback! I have the seals and I am going to replace them, I'll also check the pressure. You're too kind

[@OutboardAdvice]

@jasoncady Thanks for pointing that out - One piece of advice to anyone with this style of motor. Undo the lock nut first, just enough to nut hold the joining nut. Then undo the joining nut to remove the gearbox. Don't move the locking nut from here. When you install the gearbox, do the joining nut back up then nip up the lock nut. This should keep the shift rod in the same position as before. If you put it back in a different position, the gear shift linkages can be out of adjustment.

[@johndoe-uf9pu]

good vid with a good camera positions, the rv silicone to prevent the exhast gasses is one of my problems. thx for the info

[@b0wlez]

This video really helped me! 😊👍

[@ChrisKane-et9dc]

Simple and to the point, Very good info, thanks

[@jasoncady]

@OutboardAdvice I am in the process of doing a Mercury 50 and on my motor there is a nut that you have to loosen on the shift linkage. It is on the front side of the lower unit and is accessible prior to loosening the other 5 bolts holding it in place. I had the same problem as another person here where it only dropped down about and inch or too unit I disconnected the shift linkage. Hope this helps someone else with a similar motor in the future. Great video by the way.

[@OutboardAdvice]

@petieohalloran The pressure relief valve is a valve that 'pops' off it seat when the engine rpm is increased which increases the water pressure. It bypasses the thermostats etc and make the motor run cool at higher rpm. It has a rubber grommet that gets squeezed in by salt build up and pinches on the plastic valve. There is also a diaphragm that needs servicing/replacing if it is stretched, perrishing or gets a hole in it.

[@OutboardAdvice]

@keithblade Good luck! Let me know if you have any questions... Most important is making sure you get the water tube in and the gear shift shaft lined up when putting the gearbox back on...

[@universal1star]

Good Onya Geoff……… needed those tips 😊👌👍

[@Philiphfisch]

Very good vid!! Thank you from Italy. I'll do on my engine next week.

[@SeabassOutdoors]

we need more people like you in this world

[@deboralacreta]

awesome video. gives me the confidence to go ahead with this repair.

[@zgetz444]

Awesome job with explaining how to do this job, it almost looks easy.

[@alangiovaniromay5115]

thanks for your time to share such a good video! Cheers

[@petieohalloran]

@OutboardAdvice thnx mate for that information, you are the only one who could give me results on the problem.your a wizard

[@markdm180]

Thank you very much for the video. It was very informative and made changing the impeller a breeze.

[@OutboardAdvice]

@Dualcats2 Similar... You will need to undo the gearshift rod under the carburettors before you can take the gearbox off your motor. It will be a 1/4 inch bolt that you will need a 3/8 inch socket to undo.

[@kennethmongey6994]

Great Video. Really learned a lot. Thanks

[@WolfDogs]

Nice video clip. It saved me money taking it in to the shop.

[@elbaspelle]

Excellent tutorial! Thanks!

[@ericx122]

Oldie but goodie, thanks a lot!

[@335i101]

Kevin Knox....great question....I was going to ask the exact same one (you even got my model year correct ;)

[@danielgray2028]

Thank you for this! It helped a lot

[@Makeshift-garage]

Thanks bro your video gives me some good direction, I'll let ya know how I make out :)

[@jesussaralegui8725]

esto es buenisimo, cojonudo. Enhorabuena colega

[@OutboardAdvice]

Yes is the same procedure for the gear shift :)

[@Goldnugget47]

Thank's for the video, really informative, I have a 2016 tracker pontoon with a 90 hp 4 stroke Merc. doing a 20 hr service, every thing went well till I tried to go back up, got nut's started but when I went to tighten hit a brick wall , think shift shaft's aren't aligned properly couldn't get shifted into forward before dropping lu figured it would go back the same, didn't, I noticed my motor just has a short splined shaft did part stay in upper leg? I was within half an inch of up propeler turned motor, I believe water was right, could turn shift shaft and raise it so I don't believe it was stuck. any help or idea's greatly appreciated. David O

[@bethpajkos1046]

Thanks for the video. I have a 1982 Ventura Vendetta with a 115 hp Mariner outboard. It has been sitting (covered) for over a decade. Would there be many differences between changing the impeller on the 115 hp Mariner and the one you show in the video?

[@jerrymagri7164]

excellent video , very easy to understand , thanks

[@advancednutritioninc908]

Very Well Done!! Great explanation !! Thank You!

[@bencooke29]

@tasmania105 I had the same problem. the drive system is spring loaded and it went into forward drive when you took out the shaft because the gears are spring loaded. I haven't had time to figure it out yet but some how you need to take the lower end off again and try and figure how to put it in nutrel be for putting the shaft back in. It may take two poeple to do that so one person can hold it in nutrel while you put the shaft back up into place

[@niklasgrundel7366]

Great vid! Can you please tell me which Loctite RTV you where using sealing exchausts from impeller. Thanks in advance!

[@pbottjen5283]

Very helpful, Great job!

[@NathanHopp]

Great video, very informative. Thanks

[@tommyolsen4315]

Really great video. I`m about to change the impeller on my 75HP Optimax. But some people also put some silicon on the seal kit on the impeller house, is that really necessary? I thought the metal seal and paper seal should do the sealing itself.

[@rchenderson2000]

Great video. thanks for posting. Just what I need to rebuild the water pump. thanks again!!!!!