Finally got around to doing one job that I wanted to get taken care of last fall. Change out the water pump and impeller on my 2000 Mercury 150HP XR-6. I see the question pop up here every once in a while asking how hard of a job is it to do. My reply is – if you can change out the front brakes on your car, you can do a water pump/impeller. My owners manual recommends changing the impeller every 100 hours or once a year. I have been doing mine every other season of use and don’t feel I’m stretching my luck.
Here is a before shot:
First thing to do is go to you dealer and purchase a water pump – impeller kit. Make sure to get the entire kit with all of the gaskets, not just a new impeller. It’s my opinion that you may as well change out all of the parts rather than just swapping out the impeller. Why not do it right since you have the lower unit torn down anyway? My kit cost about $40.
Once you have the kit which contains the pump housing, gaskets, pilot tube and impeller gather the necessary tools. All you need is basic tools such as a socket set, screw driver, rubber mallet and of course a cold one! It’s also a huge plus to have an extra set of hands. In my case I had Gary Wellman over to tackle this 6-pack job.
First and most important – Put the motor in FORWARD gear.
Next, remove the zinc alloy disk and expose one of the retaining bolts under the cavitation plate. Working around the lower unit, remove all of the bolds being careful not to let the lower unit drop to the floor. (This is where a second set of hands help out) Once all of the bolts are removed, a few taps with the rubber mallet will separate the lower unit. You may need to separate the water line that operates your speedometer at this point too.
A bench vice is very helpful to hold the lower unit in place while you remove and replace the parts.
Start out by removing the 4 nuts that hold the pump housing in place.
Apply firm upward pressure until the pump housing separates. Slide the pump housing and impeller up and off of the drive shaft.
Here is a look at the old pump housing and impeller.
Old and New impeller.
Next, remove the gaskets and keep them in order so you can use them as a guide when replacing the new gaskets. My pump has 3 gaskets.
Replace the new gaskets in the exact order and configuration as the old one’s were removed.
Note the location of the retaining key for the impeller. Slide the new impeller on to the drive shaft and over the retaining key. This will prevent the impeller from spinning on the drive shaft.
Next, slide the new pump housing down the drive shaft and while turning the drive shaft in a CLOCKWISE direction, press the pump housing over the new impeller.
Replace the 4 nuts securing the pump housing in place.
Next, place the new pilot tube in the pump housing, and slide the new “Slinger” gasket down the drive shaft sealing up the water pump.
Now, with your extra set of hands, line everything up and slide the lower unit back onto the motor. You may find that you will need to turn the drive shaft slightly in a clockwise direction to line up the splines to the power head. Make sure your shift linkages are in place and reconnect the speedometer line.
Replace all of the bolts and tighten everything up. Drop the motor out of gear. This will tell you if you have the shift linkages hooked up correctly. The prop should spin freely at this point.
A final touch up of new paint and she is good as new.
When you first run the motor, check for water flow out of the pee hole. You are done! Now finish off that beer!
-------------------- Jon Jordan
In-Depth Angling Field Staff & Site Moderator.
jonwalleyejordan@hotmail.com Phone: 651.343.9318
I just did my 115 and 9.9 yamy last night also.I was really pushing my luck as they are both 1994 and had the original equiptment.I was realy surprised that the 115 impeller although stiff and a little wear wasnt that bad and the 9.9 looked like it didnt even need to be changed.One reason for this is I absolutly never start the engine out of water.I only changed the impellars as the other parts of the housing were fine.A couple things will ruin the housing overheating and sucking up sand threw the impeller.You will be able to tell if they need to be replaced.Some motors like my 9.9 require disconecting the shift linkage also.Each motor took about an hour.Now I should be good till 2015.
Great Post John. I was wondering if I could tackle the job, now I think I can! At least that is half the battle. I like all the pics, you know us guys, we like the visuals !
Excellent post. Really like the part comparing it to a brake job - I paid to have mine done and thanks to you taking the time for pictures and step by step instructions I know I can do it next time. I probably won't wait as long to change it either. Thanks again Jon.
So what does a worn impellor look like. Took mine apart last year just for the heck of it and didnt see any nicks, gouges or wear on the impellor so just put it back in. On my 25hp honda this was about a 30 minute job. Pretty simple.
Putting the motor in Forward is a very important from what I have seen. Not much to worry about with the honda since it is exposed and there is just a rod coupling and a back up nut holding it together. Tightening up the bolts with out the linkage allined can be bad. Broken housings, linkage pushed up in the motor. Uck. It gets bad when a simple job goes wrong.
Quote: So what does a worn impellor look like. Took mine apart last year just for the heck of it and didnt see any nicks, gouges or wear on the impellor so just put it back in.
I look for nicks, gouges and wear also but the main two things that I look for is:
1: amount of time since last change
2: The impeller will get dry, hard and brittle
I change my little motor impeller every other year. Just to be on the safe side since it is fast and cheap. Usually when they get as curved as Jons I think that it is time.
Great job Jon
Ron
-------------------- I'm not a complete idiot, some parts are missing.
For those of you who paid a shop to have it done what was the cost?? That will give us DYI guys a better feel for savings. Great series of pics and description Jon.
-------------------- Some drink at the fountain of knowledge. Others just gargle.
What happens if I don’t change the impeller and it goes bad? I would expect the heat sensor to send a signal to the engine electronics which would in turn put the motor into “slow mode” so it would not over heat. So I slowly limp home. If no harm is done to the motor, then why not wait until it goes bad? I guess if you have a big trip planned then it may be nice to have it done as preventative maintenance. For the local fishing that I typically do, I guess I would just lose a day of fishing. Am I missing something here?
Some older models do not have a temp sensor and if you are not looking at the water flow from the motor then you can blow or burn up the motor. Plus I would rather change it now then when I am supposed to be fishing. I do know alot of people that wait till it goes out and then fix or take it in, personal choice. Ron
-------------------- I'm not a complete idiot, some parts are missing.
A dealer will usually charge an hour of labor plus parts. Labor is going at $80 and hour. (Some place more, some less)
Dave, as mentioned, the impeller will become cracked, worn or brittle. Also, if you suck sand up in the impeller, you will see scratches and gouges in the pump housing. Also, in one of the top shots, you will see one of the gaskets had a section worn out. I think we all know someone with a motor 4, 5, or even 10 years old who has never had it serviced. I guess for me it's just cheap insurance!
If anyone in the Eau Claire, WI area would like to be my "extra set of hands" I'll be glad to supply the sockets, screwdrivers and longnecks. Heck, bring your boat down and we'll do them both! Send me a PM if interested.
I should mention that my 3-year old impeller was in fine condition but it's one of those things you might as well replace if your going to take the time to look at it.
i think you are a life saver guy. you sure got my attention, i don't remember mine being changed ever, course maybe i forgot too. i have 400 hours on my efi 150 merc, bought in the fall of 94. i called starks right away which is where i bought it, the parts guy told me my manual says every 300hours, which still seems way too many. i told him i am 100 over that, so i ordered the kit monday and it was here tues before noon. i can't get it changed out until after the 14th. now i'm afraid to use it till i get it replaced. though i have never seen any circumstances saying to change me. i do know my luck though i personally owe you one , thankyou
Excellent post Jon! I have tackled several of these in the past years and must say that its a good project for someone that has never done one before. Save yourself some monay from a dealer doing, especially when they charge $60-$90/hr?
Jon, We should take that "How To" post and put it into its own forum and start a library of these kind of boat maintenance projects! I could see it being real useful for everyone here!
Quote: What happens if I don’t change the impeller and it goes bad? I would expect the heat sensor to send a signal to the engine electronics which would in turn put the motor into “slow mode” so it would not over heat. So I slowly limp home. If no harm is done to the motor, then why not wait until it goes bad? I guess if you have a big trip planned then it may be nice to have it done as preventative maintenance. For the local fishing that I typically do, I guess I would just lose a day of fishing. Am I missing something here?
Dave, there is no "limping home" when the pump goes out. It will overheat at idle or revved up. I don't know how long it takes them to overheat. But in one minute they get pretty hot. Two minutes? Five? Something will start to give.
I paid $100 to have it changed on my 60 hp Merc 2 stroke in early December 2003. It would have cost more if it was done during a more busy time of year.
Man that was a great play by play, nice thread Jon! I need to do that to my 175 rude. Gotta love pics with instructions!! My boss let his pump go too long... now he is headed to Okoboji next week as a non boater!
Quote: JJ, One of my all-time favorite posts here at IDA!
I agree Wade! I referred to this post late last summer for work on my Merc 25 hp. Thanks again Jon, it was very helpful. In this case, pictures made the difference in me getting the impellar pump replaced properly in a timely manner.
Do you make appointments JJ ??? I guess for me I would have to be with someone like you that done it a few times to make sure I do it right . That's just me . Thanks Jon for the post .
Great post Mate! I just did mine. Probably would have gone a little quicker with a engine manual and extra set of hands. But your explanations and pictures were more than enough. (given that I hadnt ever had a chance to do this type of Maint on a boat motor, I'm pleased with the outcome.) thanks Larry
Very timely, I had called last week and made sure that the dealer had a kit in stock for my 2000 90hp Honda. I just hit the 300 hour mark, so its time for a new one. Has anyone that's done a honda found any differences in the dis-assembly than what is shown here (excellent demo by the way)?? My only other question.....is a 12'er of kokanee a suitable substitute for the Leinie's?
Tonight I followed this for the second successful time. Can't seem to remember which way to turn the drive shaft when pushing the cup onto the impeller.
Your pictures and procedures were very helpful. Now I have some questions about the reinstall procedures: 1) Is the gear connection next to the speedometer self aligning or do I need to turn it to align the splines? 2) Once everything is in place, how do you get the lower unit to mate with the shaft body (housing between the power head and the lower unit)? I can get the lower unit up to the housing but cannot get the last 3/4 to 1 inch to close. When I took the unit apart I had to gently pry the lower unit off the shaft housing. 3) I didn't follow the directions and took the lower unit off without the shifter in forward. How (can?) do I recitify this during reassembly?
First, let’s start out with question #2. You should be able to turn the shaft clockwise to align the splines with the base of the motor head. Another option would be to turn the flywheel. If you elect to turn the flywheel, make sure you pull the kill switch. Once the splines are aligned, the lower unit should slide right up into place.
For #1 and #3. Typically, if the motor was put into gear, the shift linkage will also slide right back into place. I’ll assume you left it in neutral and did not change the gear setting on the lower unit. (In other words, you did not put the lower unit into gear while off the motor.) If that is the case, slide it back together and keep your fingers crossed. Now, the prop should be spinning free. (out of gear), and shifter in Neutral. Put the motor in forward, that should lock the prop in gear. Again, as long as the lower unit was not put in gear while off, you should be ok. If it was, then you may have a problem. Usually what happens is when you put the shifter in forward, the motor goes in reverse and visa-versa. If that is the case, drop the lower unit, put the lower unit in forward gear, put the shifter in forward gear and reassemble.
Thanks for the response. First, thankfully(?) I didn't shift the lower unit while it was off. It was in neutral when taken off and still is, the prop spins freely. Next, when we pulled the lower unit off we had to gently force (pry) the unit off the motor. Now when we get the lower unit up to the point where the bolts align into their holes, and the shift linkage almost touches, we can't get it any farther. It doesn't seem to be the shift linkage stopping it because we can still move them apart. The water tube guide sleeve is over the water tube. There is resistance as though something is keeping the lower unit from sliding into place, we have applied a fair amount of effort to force it together. We are left with about a one inch gap. Is there something else we are missing that needs to be aligned or is this a result of the drive shaft splines not aligned?
Most likely it's the splines. There is zero tolerance in that connection. The splines need to align perfectly and will slide in snug. Remeber, that shaft spins at 6,000 rpm's with a lot of torque!!
Jon, you were correct. By bringing the lower unit up until where we had resistance and wiggling the flywheel the splines slipped in and everything went together nicely. The new water pump is working fine and the motor runs like it always has.
Thanks again for the help, first time for that job for me.
Have you ever changed the seals that go on the drive shaft and keep water out of lower unit oil? I'm getting a small amount of water in the lower unit oil and I've taken the prop off and that seal looks good. I can't see any fishing line or anything that looks bad. I've also installed new plastic washers under the fill and vent screws so they should be good. My only other guess is that perhaps the seal(s) on the drive shaft are leaking. Are they difficult to change or do you have any other ideas where the water could be coming from?
I’ve never done seals. I believe you need some specialized tools for the job. First step would be to take the motor in and get a leak down test done. That test will identify where your problem is.
My Web Server is off line right now. Actually this is day 2 of the outage. When the server comes back up all of my web links will be restored, including my pic in my profile!
Hi Jon, I found this forum looking for info on how to change my water pump impeller on my 50 Yamaha jet. Will it be the same for my jet? Just drop the jet housing from the bottom of my motor? Thanks, the info you posted with the pics was great! Just a little neveous about trying this the first time.
Just wanted to say thanks Jon Got done with my 40 hp merc. First time for me. Everything was smooth. The splines took a litle bit, the Mrs. help with that. Can you post the same type of pictorial for catching walleyes on pool 2
I know this thread is old but it's a good one. Recently did a complete water pump kit in my 87' Mariner 50HP for the first time after owning this boat for 5 years. Found this thread after the job was done, but didn't encounter any problems other than needing my brother to help me re-install the LU.
Old impeller showed considerable wear and distortion, as well as one paddle (under my index finger) almost broken off. I know this thread will help other first timers learn and save some cash so I'm giving it a bump.
I am having issues in replacing the water pump in my 30(EL) hp Mariner outboard for my Pontoon. I hav two issues 1) how do I disconnect the waterline running paralel to the shaft so I can remove and replace the water pump? I removed the 4 bolts that held the lower unit in place and can see the water pump but it could not be completely removed due to the water tube. 2) I am having difficulty in getting the shaft back in when my attemps to remove it failed. It is still hanging out about 5 inches from where it should be to fasten it in with the four bolts. I have rotated the prop ever so slightly to aligh the spines on the shaft but it is not going back in. What am I doing wrong? I had placed the speed control in forward before starting (and have not touched it since). I don't seem to be able to to get it realigned, possibly the metal water tube (mentiod above)is part of the problem? Can anyone help this novist out.
Quote: I’ll assume you left it in neutral and did not change the gear setting on the lower unit.
Hello, I just followed your guide which also was my first time, installation went fine.
Problem is that we had Control Box in FORWARD Well, when the lower unit was off, my helping hands accidently switched the lower unit into reverse. We try putting it back into Forward but only goes to neutral or reverse? Seems that way. We think when we get it into FORWARD and it like "pops" out as hooking the lower unit back on. HELP!
I'd try turning the drive shaft clockwise while turning the shift linkage to forward....all one motion. Rmember, when the motor is running, that shaft is always spinning. You need to pop that clutch dog in with a littl force!
Water Pump & Impeller Replacement.
i personally owe you one 
Re: Water Pump & Impeller Replacement.
