Mercury/Tohatsu Outboard Water Pump Impeller Change on a 4HP/5HP/6HP 4-Stroke

[@MichaelSmith-mi5ig]

I’ve never struggled so hard getting this lower end unit in. Still working on it 1 hour and counting. Great video.

[@Skinnyriver]

Here is the best video on YT about reinstalling here with good pointers kzbin.info/www/bejne/qaOqh4aiacShbrMsi=3zOdqc8ZoW5Dqnh4

[@michaels1997]

Such a helpful video for impeller replacement. Replacing the unit is tricky as you and others have said. After 10 minutes of trying, I used a cheap wireless inspection camera that I've got, pushed that up the leg to find the location of the drive shaft tube and guided it in with that - done in moments. It's a Depstech camera - cheap and cheerful but really helped. Thanks again from the UK!

[@Skinnyriver]

Yeah it’s super tricky, it’s the most frustrating part. That camera is a genius idea!!!

[@brantbuchika9391]

Great video - especially the parts about the impeller pin and misaligned shifter - those are the hints us novices need most!

[@Skinnyriver]

Yeah I made a lot of mistakes! Hardest part of all of this is getting the lower end unit lined back up and reinstalled. The drive shaft and cooling water pipe have to line up with motor perfectly. It’s a pain. Thanks for the view!

[@kd7jz]

At the end, where he talks about that lever that can change gears in the lower unit by moving that rod up and down is the key. That rod actually comes up in forward and releases a latch to let the motor tip forward. If you study it, you can see that when you are in neutral, the top of that rod just touches that release. So, you can use that to know what position the transmission is in after you put it all together. Great video by the way!

[@Skinnyriver]

That’s a really good point, I was struggling to explain how to tell what gear the lower end unit is in by looking at the rod extending up to the tilt/trim release. But you said it perfectly, if it’s up it’s in forward, if it’s touching it’s neutral, if it’s down it’s reverse

[@great0789]

I will be doing this in a few days on the new-to-me 2004 Mercury 5hp 2-stroke I just got for free. This has barely been used and been sitting in a garage for the last 5 years. Looking forward to having my first boat up and running within a few months. I already know what hull I shall be attaching it to. I shall be stalking fish with the kids in not time!!!

[@Skinnyriver]

Awesome congrats, let me know how it goes!

[@great0789]

@@Skinnyriver Sure thing! Thank you. I may upgrade to the 4-stroke in a few years though… maybe even a 9.9hp. A bit less simple of a machine…. But it will help out at times when traveling long distance in my waters.

[@theobirkholz]

I'm also having trouble with the lower unit shift linkage. It is a real pain in the ass. Thanks for the video, it is good to get some another perspectives on it

[@Skinnyriver]

It’s the worst. It took me at least 45 mins the last time I did it. I really haven’t learned and big tricks yet to make is easy

[@scubadoonorway4960]

I struggle to it was a pain i use steel wire to point it right.

[@Josephsaviationvp]

Hi great video…i have a mercury 6hp 4 stroke. I changed the impeller without any issues. Question, what is the procedure to get the drive shaft rod back up into the engine crank. I’ve tried repeatedly to get the lower end back together and there seems to be something blocking the engine inlet where the shaft splines fit. What do you recommend? Thanks

[@Skinnyriver]

It’s a real pain sometimes. This vid helped some kzbin.info/www/bejne/mYubpp2FeLdpmJosi=7Z2oB-GhdZFk-TF_ Also putting a ratchet strap around the lower end unit and the upper end (actual motor) can help keep it in place while you get everything aligned

[@vincentsweeney9667]

Nice! Just picked up a 2001 5 two stroke. Good lessom!

[@Skinnyriver]

Awesome! Hope you enjoy your new motor!

[@SavedByGraceFarm]

I have the same motor Vincent listed. Is the process the same for the 2 stroke and 4 stroke motors? I imagine so for the impeller.

[@Skinnyriver]

I’m pretty sure it’s the same. There might be some minor design differences but process should be similar

[@williammurray4315]

You mentioned a link to a video that shows how to get the impeller key installed. I’m having a heck of a time!

[@Skinnyriver]

I don’t think that video is on KZbin anymore. Some people will use a dab of grease to keep the key in place then push the impeller down. Here is another video of a guy that uses an oring to keep it in place kzbin.info/www/bejne/bYW1gp5-mZlpa6csi=JpNvPE0Cxfl_h35z

[@williammurray4315]

Got it! Marine grease is sticky enough to hold the key in place. A little finesse and patience does it. Adding a bit of grease to the impeller’s fins will help move it too upon start up. Thanks!

[@williammurray4315]

So now my issue is lining up the gear shaft so that the lower unit seats correctly with the upper. I though I had it, but when I turned the propeller, I heard a clicking sound. I did turn the flywheel, tried lining it up in forward, neutral and reverse but no luck. Any ideas?

[@Skinnyriver]

@williammurray4315 kzbin.info/www/bejne/qaOqh4aiacShbrMfeature=shared this guy is awesome explaining it. Thai was the hardest part of the whole process. It took me 45 mins trying to get mine back installed. Turning the prop will help it seat down, keep trying it will fit up eventually

[@MrPMOSullivan]

Very well explained. I can't remove the bottom half. Seems stuck up in the drive shaft. How do I loosen it?

[@Skinnyriver]

Make sure the shift linkage coupling is undone. If you are sure everything is undone then you can get a rubber mallet and try to tap it loose. Or get a pry bar to add pressure while to hit it with a rubber mallet / dead blow. Some people use wood or plastic wedges. Make sure you put antiseeze on the shaft end after you get it off so this doesn’t happen again.

[@svaty9205]

Very informative video. You say the impeller turns clockwise, but what happens when you go in reverse?

[@Skinnyriver]

Some people say it doesn’t really matter and the impeller will correct itself but worst case it will not circulate enough water and you will have motor temp problems. Regardless always check water coming out of your motor every time you go out

[@ashleydang3650]

Hi, I like all of your videos; there are very helpful. I have the same motor and I feel the motor is too hot after 15 minutes run. Does this motor have a thermostat? If so, where does it locate? Thank you.

[@Skinnyriver]

Yeah it’s screwed into the block I believe on the right side. I would definitely replace it and the gasket. They are really cheap. If it’s not the thermostat then it’s either a clog or damaged water pump impeller

[@ashleydang3650]

@@Skinnyriver Thank you for the info. How often does the thermostat need to be replaced? Have you changed yours? Mine motor is 2018.

[@Skinnyriver]

Mine is a 2018 and I have not changed mine. They should last many years. Do you get a lot of water flow coming out of the motor? If you get a lot of water flow then it is the thermostat You can remove it to make sure there is not trash around it keeping it from opening and closing

[@ashleydang3650]

@@Skinnyriver The water comes out very strong and seems normal. The block feels very hot, even the carb is hot too. I am hoping it’s a thermostat issue and easy fix. Thanks for your advice, Sir.

[@Skinnyriver]

Yeah sounds like thermostat. Good luck! Should be quick and cheap fix. Here is a parts diagram that shows the thermostat location and it’s part number www.perfprotech.com/mercury-marine-parts-catalog/cylinder-block/assembly/11768/90?model=4353 Item #20

[@espedale]

There is a video on another channel where a guy disconnects the line from the fuel pump to see how long it takes to prime by pulling the start cord with internal tank fuel vs using a priming bulb from an external tank fuel supply. It took like 16 pulls with the internal fuel tank to see fuel post-fuel filter, but with the external tank you prime using a priming bulb on the supply line, resulting in instant fuel delivery post fuel-filter. That is why it took you so long to get her started, not due to any mechanical error, but due to the fact you are using the internal fuel tank and the cord to prime. This is an expected behavior.

[@Skinnyriver]

Yeah I learned this too. I now prime the system with an external tank before I leave then switch over to the internal tank or just use the external tank.

[@Skinnyriver]

Can you still find the at video? I would like to see it as well

[@espedale]

@@Skinnyriver Yes! Start at around 6:00 minutes in. kzbin.info/www/bejne/gZyTaIira5Vlhbs

[@espedale]

@@Skinnyriver Looks like this is especially a problem when the carb is dry.

[@espedale]

@@Skinnyriver Do you have a video showing how to change the gaskets provided in the water pump kit?

[@lausagne4764]

Very good video. Thanks you very much for it.

[@Skinnyriver]

Thanks for the view!!

[@kerrywages9631]

I really like your video's, very detailed & helpful. I have a 3.5/ 4 stroke Mercury that is not peeing & i think it is the impeller. Is the impeller change out process and driveshaft attachment the same as the 4Hp/ 5hp demonstrated in your video?

[@Skinnyriver]

Yeah if it’s a 4 stroke then it should be the same. One warning getting the drive shaft lined back up and seated back to the motor was FRUSTRATING. the one big complaint I get is I didn’t cover that process enough. It just takes a lot of patience, just a heads up. I’m not aware of any tricks. But yeah there are really only 3 things it could be (impeller, water outlet clogged due to insect nest, or you sucked up something on water inlet). 99% it’s the impeller

[@Skinnyriver]

And make sure once you’ve undone the coupling on the shifter linkage rod, don’t change gears on the upper end or the lower unit or it will be out of sync/position when you put the coupling back on

[@kerrywages9631]

@@Skinnyriver Thanks so much for your input and advice...I look forward to keeping track of your future videos

[@brochman8307]

You solved my problem to why my outboard wouldn't go into reverse gear after doing an impeller change. Thank you as i was really scratching my head trying to figure it out.

[@Skinnyriver]

Good deal, glad you found the issue and got your motor fixed! Thanks for the view!!

[@alese3k]

Is the only possibility to flush the cooling system with fresh water, to put the engine in a barrel? I can't find a way to connect the hose because the water intake is directly above the propeller.

[@Skinnyriver]

Yeah I’m struggling with this as well. To flush the lower end unit I think putting it in a barrel is the only way. There should be a hose connection below the engine cover where you can hookup a hose fitting, but I think that only flushes the engine block. If I figure it out I’ll I’ll let you know

[@renaykung3542]

Awesome video. You got me out of trouble. Thanks heaps

[@Skinnyriver]

Awesome, I appreciate the view thanks!

[@adamrobbins9756]

Hello Iv lost my gear how do I get them back dose it have to be in reverse and push the metal rod down and clamp it I’m not sure what todo

[@nicklausmisiti5204]

Unfortunately i didnt see this until after i screwed mine up. What do you do if you change the gear and cant get the linkage to connect correctly.

[@Skinnyriver]

Try undoing the rod coupling screw, push the lower end units rod all the way down, this should put it in reverse. Then put the shift lever in reverse. This should get them back in sync.

[@holymotherofgod1]

With my lower unit off, the shift rod only changes between 2 positions.. feel like it should be able to switch between 3? R/N/F Any reason why that rod wouldn't move between 3? When I have it installed I can't push that rod down any further, it stays in Forward. I pulled it all back out and same thing

[@Skinnyriver]

Mine did this, it probably means that the lower unit gear position and the upper shift lever are out of sync. Loosen the coupling, push the lower units shift rod into reverse, then shift your shift lever into reverse and retighten the coupling

[@holymotherofgod1]

Ever take a break and come back to something that wasn't working, and now just goes smooth? What's the word for that? Haha Thanks again SkinnyRiver 🤙🤙

[@Skinnyriver]

All the time lol

[@dennisglorius7429]

I didn’t get what the problem was after changing why it didn’t started. You said don’t change the gears but you didn’t right? Can someone explain please. I’m No native English

[@johanwithag2432]

I must say, that impeller pin construction is much better engineered with the Yamaha 4/5/6/ Hp 4 stroke engines. Its also a removable "pin" but much bigger and there is no slack. And these motors have a internal primer ball special for use with te internal thank. That solves the problem from draining of the carburator and that you have pull 5/6 times to fill it up again (i saw your video on that one). And they provide two opposite acces holes to loosen the gearshift (more comfortable). I own a 3.5hp 4 stroke Tohatsu, no complains so far. But I'm always interested in the engineering part of these engines.

[@Skinnyriver]

Good points, I’m tying to get my hands on a Yamaha 6hp to do a comparison. But don’t want to drop $1500. Yeah a priming bulb would be nice on this little Merc. Good point on the impeller key. I was lucky I found mine after I dropped it

[@johanwithag2432]

@@Skinnyriver Yea, I'm surprised that flimsy pin construction can manage the forces of this impeller and hold it in place. I see more subtile and better thought out engineering solutions with these Yamaha engines. But you have to pay a higher price for it. Here in The Netherlands I can buy a new 6hp 4 stroke Tohatsu for about 1200 euro and have to pay 1600+ euro for a comparable Yamaha engine. Tohatsu dropped the internal tank in their latest models and I can imagine way.

[@Skinnyriver]

@johanwithag2432 if you have any video ideas for the Tohatsu / Merc or general small boat stuff, let me know! Running out of ideas until I can get my hands on a Yamaha

[@johanwithag2432]

@@Skinnyriver Hi, I looked over your video's. Maybe Gasoline would be a candidate subject. The number one reason people get in trouble with these modern small 4 stoke engines is a carburator lock-up due to bad/old gasoline. As a non regular user of my engine I exclusively use 4 stroke Aspen gasoline. It's ridiculously expensive but it stays fit-for-purpose for years. I see the guys in Scotland that go out to sea 10+ miles with these small engines all using the cleanest gasoline they can get (and free of any bio crap adding stuff). I let you know when other subjects come to my mind.

[@Skinnyriver]

@johanwithag2432 yeah great pt thanks. Gas with ethanol has been my enemy with this and other small motors. Thanks

[@sunsetatshabooms4558]

Is it normal for a small amount of water to come out of the plug where u connect the shifting rod together?

[@ncwarrior62]

Good job great educational video!

[@Skinnyriver]

Thanks! I appreciate the view.

[@ia6980]

Another question please, can you just clean impeller? instead of changing it? I've taken my 6hp to ocean once and engine started to bog down at acceleration after that. Tohatsu manual says that insufficient water flow can cause poor acceleration? I'm thinking maybe salt build up clogged part of impeller? ....I've noticed good stream of water peeing at low speed but at full rpm water is sputtering .....My engine is brand new 2023 barely used and it has bogging down/no thrust issues at 3/4th-full throttle speed, any suggestion? would greatly appreciate!!

[@Skinnyriver]

Yeah you can clean it, but honestly I doubt there is salt build up on the impeller itself. But you can take it apart and make sure you didn’t suck something up (trash) and clean if needed. I really doubt it’s water flow though. Motor should still accelerate even with No Water until it gets too hot then it will start acting crazy and bogging. If it starts to bog after you run it a while and it’s hot, then a it might be water flow. My water stream at full speed also sputters just because of the turbulence at that higher speed. Has it ever ran great at full RPM and only started doing this when you went into salt water or was this the first time you have taken it out?

[@Skinnyriver]

99% of bogging issues are either fuel flow issues or contamination in carburetor here is a vid about bogging kzbin.info/www/bejne/hpTNgH1rlqmHg6s

[@boating_on_a_budget6026]

Hey, I just changed my impeller. I’m a total idiot and took it out of reverse while the lower unit was out. Shift shaft is not lining up anymore. Any tips?

[@Skinnyriver]

Yeah that sucks. You’ll need to undo the coupling that connects the upper shift rod to the lower shift rod. Force the lower shift rod down then shift the shifter lever to reverse. Finally re-tighten the coupling. That should get everything back in sync

[@Skinnyriver]

Or if you can figure out what gear the lower end unit is in, undo the coupling, shift the shifter lever to that position and then re-tighten the coupling. That should get it back in sync

[@michaelg8359]

First you said clockwise then counterclockwise Which is it?

[@Skinnyriver]

clockwise

[@sailingcitrinesunset4065]

Nice video thanks for sharing

[@Skinnyriver]

Thanks for the view, I appreciate it!

[@brianvicknair810]

So after u changed impeller was it pissing warm a little and is that ok?

[@Skinnyriver]

As long as water is flowing in a pretty constant stream you should be good.

[@JakovHancevic]

super

[@nicklausmisiti5204]

Thx. What if when i push the rod it wont go down

[@nicklausmisiti5204]

Thx. I ended up getting it. In case anyone else has this problem it wouldn't go down by hand but when I used a tool with slight leverage it went down no problem. Thx for the help skinny river

[@Skinnyriver]

Glad you got it !!!

[@outdoorman7425]

will this be different on a mercury 5 hp 2 stroke?

[@chrisabella624]

Anyone have a lead on where I can get an engine cowl for this exact engine. We had a little mishap and mine is now gone.

[@ia6980]

question please, is it ok to use mercury propeller for tohatsu 4stroke 6hp? (i want to change it to 7.8x7 from 7.8x8 for better accelaration) since dealer don't have that one in stock, and mercury does. ?

[@Skinnyriver]

Yeah I’m 99% sure they are interchangeable. The only thing you need to watch out for is when you go down in pitch size it will increase your RPMs on your motor (that’s where you get the more power) but I think a lot of people do this change

[@Skinnyriver]

There is an online table from Mercury that shows the prop options, I’ll try to find it

[@Skinnyriver]

Here is the Tohatsu prop PNs. I am 99% sure they are the same as the Mercury props www.tohatsu.com/marine/int/accessories/prop.html

[@ia6980]

@@Skinnyriver thanks a lot!

[@ia6980]

@@Skinnyriver thank you

[@mikeyhemkens8889]

What’s the part number for a 6 hp 4 stroke

[@Skinnyriver]

Double check your model # compatibility on boats.net but mine was 8M0204676

[@arnefourie118]

I need help. My engine doesn't pump water, but when i remove the Grommet to loosen the selector, it's pump a solid stream. So it's telling me the exhaust gas is blowing the water away? Also not seeing any exhaust gas coming out of the propeller. Anyone help please? 😅

[@Skinnyriver]

That is weird, sorry I don’t know. Hopefully someone has seen this before.

[@arnefourie118]

​Found the problem. Thank you for the response. It was the exhaust gas relief that was giving me issues @@Skinnyriver

[@thatonekidkeegan5097]

Thanks for the link

[@thatonekidkeegan5097]

Sarcasm

[@Skinnyriver]

Man this vid is a couple years old. The original links to some of the parts no longer work. What do you need? Link to the Mercury impeller?

[@apolloscrubbed2708]

I lost my rubber cover when replacing this. Do you think any cover would do? Or do you know where I might be able to find one?

[@Skinnyriver]

Check out this diagram www.boats.net/catalog/mercury/outboard-by-hp/6hp/0r411838-up-usa-cat-90-8m0056559/gear-housing-driveshaft

[@apolloscrubbed2708]

Will do sir! Thank you!!

[@Skinnyriver]

If you can’t find, let me know. Honestly I’m not sure which rubber cover it is. If you let me know at what point in the video (minute and second) shows the cover I can help find it

[@Skinnyriver]

If you find it on the diagram it will give the part number and you can do a google search for the PN and probably find it on Amazon or eBay for cheap

[@apolloscrubbed2708]

At 1:08 it covers the shift linkage

[@misterxf3388]

01:50 "10mm socket, yeah I have got that right here . WTF. . .where is that F@c&ity F@c&in' 10mm socket ????"

[@Skinnyriver]

Yeah everytime, I may have done some creative editing to hide some f@&#’s for not finding tools

[@kgolightly1]

Is there a secret to lining up the shift rod into the upper hole when reinstalling the lower unit after putting in the new impeller. Frustrated!

[@Skinnyriver]

This was the most frustrating thing for me too. I searched and searched but couldn’t find any hacks to make this easy. I did find turning the prop could help the gear tears line up. But honestly it took me a good 30 mins to get everything to finally line up. It will, I promise. Make sure the motor can’t tip over. It’s too heavy with the lower off and you are pushing. Easy to tip

[@iveraldorodrigues9601]

Como comprar este motor valor?

[@Skinnyriver]

cuesta 1800 nuevo. puede comprar en tiendas náuticas locales o en línea en onlineoutboards.com

[@NewtontheSailordog]

Nice video. I know how happy a Mercury owner if the engine start at the first pull. (Yamaha owner: 🥱) 😄🤣

[@Skinnyriver]

lol 🤣

[@jeffkurina7058]

​@@SkinnyriverI accidentally unscrewed the Linkage bolt and the brass clips fell down. Any suggestions on how to get it back in place or video link you could send me I'd appreciate it 🙏