Replacing impeller on newer style Merc raw water pump

[boatrboy]

I started pulling my seawater pumps to replace the impeller last week. I was told by the previous owner they were both replaced complete in 2021 but I wanted to start this year with all maintenance items done by myself.


I noticed these brass pumps have stainless steel plates embedded where the ends of the impeller rides. I tried to pull them out with my fingernail only, but it did not seem to move. Do they just need a little force to remove them or are they glued? They look ok but I wonder when I have to replace them next change what is the procedure? Assuming they are replaceable…


I did not see a merc kit in my quick search with an impeller and these two side plates. I did see a kit with 1 small side plate and 1 large one for the outer housing, along with a shorter impeller as a repair kit for a brass model, but I seem to have a newer model?

 

[Siboatguy]

If you have them out and you really want to upgrade them... I would change them over to Harden Marine Stainless Steel pumps... They last a lot longer and are great pumps...

 

[boatrboy]

If you have them out and you really want to upgrade them... I would change them over to Harden Marine Stainless Steel pumps... They last a lot longer and are great pumps...

Actually I wasn’t looking to upgrade them as they are only a year old and at 1k each I just wanted to make sure the impellers are perfect.
I’m hoping someone can answer my questions from my original post.

Although I will say it’s fun to spend other people’s money here - I too do it all the time

 

[paulswagelock]

It has been a while, but I thought I remembered the switch to the SS plates also made them non repairable, but I have been away from the IO motors for several years now.

 

[Siboatguy]

I believe the pumps are only around 500ish... I switched out 1 last year.. Now gonna switch out my other this year... And then Ill have a spare ready to go if need be for a holiday weekend..

 

[boatrboy]

I believe the pumps are only around 500ish...

Thanks Sib- I saw that - it’s tempting. The 1k I referred to is what my merc pumps cost complete with the single point actuator. I think the 500 ish the pump only, which would be what I would change.

Since mine are so new I’ll keep them for a few years.

 

[Tacoma290]

boatrboy: Here is a direct answer to your question:
Impellers with the wear plate on the shaft side: Mercury 47-8M0137219. This wear plate has a rubber like backing that tends to stick to the housing. Use a screwdriver to kick it loose.
The wear plate for the other side of the impeller is 8M0180871. It is held in place with RTV sealant. A screwdriver will pop it out.
Both of these part numbers work with the stock pump since the impeller is slightly less wide than the original. Based on one web site (always taken with a drain of salt), this setup may not work with winterizing.
My local Merc dealer keeps shaft seal replacement kits for the stock pumps on-hand for about $100, so I have not seen the need to switch to Hardin yet.

 

[boatrboy]

Thank you very much Tacoma!

 

[boatrboy]

Tacoma,

Where did you find those part numbers?

Tonight I decided to assemble the new impellers and thought about this post. I double checked the part number you gave and my research so far confirms that the impeller is shorter than the original one. I measured the one I bought (factory replacement number) and the one I pulled out of what I perceive to be a newer style pump, and sure enough it’s shorter.

Of course I had everything together (on the kitchen table) before the bell went off in my head. I pulled it all apart again and need to order the shorter impeller. I ask about where you found the part number as I wonder if they sell just the impeller since the plate is good, of if I have to buy the kit? I searched and see I can buy the kit basically anywhere, but am curious how you got this info.

Thanks again - Mark

 

[techmitch]

Tacoma,

Where did you find those part numbers?

Tonight I decided to assemble the new impellers and thought about this post. I double checked the part number you gave and my research so far confirms that the impeller is shorter than the original one. I measured the one I bought (factory replacement number) and the one I pulled out of what I perceive to be a newer style pump, and sure enough it’s shorter.

Of course I had everything together (on the kitchen table) before the bell went off in my head. I pulled it all apart again and need to order the shorter impeller. I ask about where you found the part number as I wonder if they sell just the impeller since the plate is good, of if I have to buy the kit? I searched and see I can buy the kit basically anywhere, but am curious how you got this info.

Thanks again - Mark

@Tacoma290

 

[Tacoma290]

We have a very good Merc tech in our area. I was about to but the regular impellers a few years ago, and he directed me to go this route. So, any Merc supplies I can get locally, I get from this guy.
No you can't buy the smaller impeller without the shaft side wear plate. Hopefully that answers your question.

 

[boatrboy]

We have a very good Merc tech in our area. I was about to but the regular impellers a few years ago, and he directed me to go this route. So, any Merc supplies I can get locally, I get from this guy.
No you can't buy the smaller impeller without the shaft side wear plate. Hopefully that answers your question.

Thanks - Last night I decided to pull the plate in the housing out as you suggested. As you noted it has the rubber type backing and popped out. While I could not find any documentation on my pump, I went ahead and ordered the kit you suggested (47-8M0137219) as the outer housing plate look good. I am hoping there is only 1 kit . When I measured the plate and rubber backing it looked like it was 0.050" thick but the impeller was noted as 0.030" thinner... We will see as the parts are underway. I am assuming that the new one will not actually "stick" to the housing, but the rubber will keep it from wiggling around.

 

[Korkie]

Saw the cut down between the Merc and Hardin pumps at tis years Miami Bot Show. Quite the difference. Will be switching over to the Hardin when the time comes.

 

[boatrboy]

So new kits arrived tonight! I had called Merc and he confirmed everything I ordered is correct - thanks again Tacoma.
The parts came with an instruction sheet which shows how to replace the outer housing insert but the kit I have did not include it. In my case it’s not needed at the condition of mine was fine. At least now I know the part numbers (Tacoma’s list was spot on).
For those who have newer pumps here is the kit. It does include the insert for the impeller housing with a rubber backing.

I am also making a plastic insertion tool to help with the assembly. As soon as it’s done I’ll post a picture. It should slide right in with some Dawn I hope.

 

[boatrboy]

So the replacement of the new impeller went smoothly. After watching the Harden video I decided to make my own install tool. It’s similar to what they sell but no need to bolt it together. I videoed me using it but can’t post video. Here is what it looks like. It’s a simple piece of Delrin machined with a taper with #10/32 set screws to land in the tapped holes on the pump. Basically I lubed it and the impeller with Dawn and pushed the impeller right into place.
The Allen wrench grips the center of the impeller flats to twist it as I loaded it into the delrin, then I just push. No need to wrestle it in or use tie wraps as I have seen. Worked well for me.

 

[Bill Curtis]

So the replacement of the new impeller went smoothly. After watching the Harden video I decided to make my own install tool. It’s similar to what they sell but no need to bolt it together. I videoed me using it but can’t post video. Here is what it looks like. It’s a simple piece of Delrin machined with a taper with #10/32 set screws to land in the tapped holes on the pump. Basically I lubed it and the impeller with Dawn and pushed the impeller right into place.
The Allen wrench grips the center of the impeller flats to twist it as I loaded it into the delrin, then I just push. No need to wrestle it in or use tie wraps as I have seen. Worked well for me.
View attachment 140934 View attachment 140935 View attachment 140936

Gotta get me one of those for my Gen5 pump. so much easier....

 

[Tacoma290]

So the replacement of the new impeller went smoothly. After watching the Harden video I decided to make my own install tool. It’s similar to what they sell but no need to bolt it together. I videoed me using it but can’t post video. Here is what it looks like. It’s a simple piece of Delrin machined with a taper with #10/32 set screws to land in the tapped holes on the pump. Basically I lubed it and the impeller with Dawn and pushed the impeller right into place.
The Allen wrench grips the center of the impeller flats to twist it as I loaded it into the delrin, then I just push. No need to wrestle it in or use tie wraps as I have seen. Worked well for me.

That tool is so great!

 

[boatrboy]

Ok so I’ll try to attach my very first YouTube video

 

[unsalted]

Question on the impeller install. Would a hose clamp at the midpoint work to compress the vanes to get it started. Then remove the clamp and twist it the rest of the way in? Your tool is more elegant but hose clamps would be more available.

 

[scoflaw]

Zip ties have worked forever. Putting that impellor in is nothing compared to removing and installing the complete pump.