Regular maintenance - change just the impeller or entire housing too?

[twr7cx]

As part of regular maintenance I understand that the water pump impeller should be changed at annually/at the start of each season. Should the whole housing unit be replaced with it, or just the impeller by itself?

The particular motor in question is a 2001 Mercury 115HP Saltwater but I'd assume this is a generic maintenance concept?

 

[Dukedog]

do tha whole kit.. stainless parts (cup in cap, ride plate) can "look" pristine but may not be so.....

 

[racerone]

In many areas ( fresh water ) a new impeller every 2 or 3 years is all you need.-----Also depends on number of hours use.------Maybe get complete kit and use the impeller only.----Have those parts ready should you see wear in the stainless cup.-----Most shops will install a complete kit because it looks good on the invoice.

 

[dingbat]

Do yourself a favor and replace the pump based on performance, not time.

Change the pump and housing the first time to get a base line pressure reading.
Make note and compare to the pressure specification noted in the manual.

In my case, a new impeller and housing runs 2-3 psi above idle specification.
I run the setup until idle pressure drops to factory recommended min. pressure or 3 years, whichever comes first. Change the housing every other impeller.

 

[racerone]

The stainless cups/ housings in my area do not show signs of wear !

 

[dingbat]

The stainless cups/ housings in my area do not show signs of wear !

Thought I had one out in the shop to show you what happens to them in salt

They get “sand blasted” in no time but it’s the piece of shell imbedded in the impeller that tears cups up pretty bad. Well past the finger nail test

 

[racerone]

A prudent owner doing his own work must decide what beer tokens to spend.

 

[wn6ngp]

The stainless cups/ housings in my area do not show signs of wear !

I have a 20 year old 90hp. Not sure why, perhaps a good design or because I don't abuse it. I changed the first complete pump kit 10 years ago despite the fact that everything looked fine. Last year (10 years later) I took it apart and everything looked fine so I put it back together didn't even change the rubber impeller. I installed a pressure gauge to watch for the future. I boat in fresh and salt. In my case I think the biggest risk is that the rubber of the impeller may get brittle with age, unless of course if I abuse it like running the motor outside of water. I have about 500 hrs on it. Its certainly worth checking periodically if for no other reason to make sure that the lower unit drops away easily. That's another story.

 

[racerone]

Some of the newer 3 cylinder motors have very durable impellers.-----But after 10 years a new one is recommended by many folks.-----Many shops will say " the customer is upset when we show an invoice with $20 for parts and $150 labor.--When we install a $120 kit at $150 labor there are no complaints and we make more money "

 

[twr7cx]

In many areas ( fresh water ) a new impeller every 2 or 3 years is all you need.-----Also depends on number of hours use.

This outboard is used in saltwater only but low number of hours a year - probably only about 8 - 10 hours annually.

 

[twr7cx]

I have a 20 year old 90hp. Not sure why, perhaps a good design or because I don't abuse it. I changed the first complete pump kit 10 years ago despite the fact that everything looked fine. Last year (10 years later) I took it apart and everything looked fine so I put it back together didn't even change the rubber impeller.

Each to their own, but if I've gone to the effort of accessing the impeller I'd replace it - especially after 10 years. Rubber has a limited lifespan.

 

[twr7cx]

A prudent owner doing his own work must decide what beer tokens to spend.

It's not so much the actual cost price, but rather also the wastage if unnecesary.
But it would seem that opinions on this topic vary greatly. I am fond of racerone's idea of having a complete kit on the shelf for 'if needed' and dingbat's data driven method by monitoring/testing the water pumps output pressure.

 

[QBhoy]

Newer merc a recommend a 300 hour change out. I’m at 900 hours and have the advantage of reading my water pressure. She’s still reading as good as new. But it’s getting changed for the sake of not wanting to push the boundaries too much further.

 

[Berdink]

I don't want to hijack this thread, just asking a supplemental question.
Do you guys put a little grease on the impeller fins when replacing it?
If so, any type grease? Vaseline work?

 

[racerone]

Grease would only help with assembly.----Water is the lubricant for an impeller.

 

[merc850]

Use dish soap it washes out of the pump, grease can be absorbed by the rubber; who knows what effect it has.

 

[Berdink]

If the housing is original and in great shape, I surely wouldn't want to replace it with something other than genuine parts.

 

[Dukedog]

tha only reason i suggested replace it all is 'cause it's not worth it ta me ta pull it again, time, labor, inconvenience ('bout 20/25 bucks difference) if one of tha "other" parts fails somewhere down tha line but ta each his own... like said, you cannot "always" tell if they are wore bad enough or not....jmo

 

[Berdink]

I wasn't really speaking on your suggestion. It's a good one. I was speaking more about not replacing a perfectly good one with possibly an lower quality aftermarket one.

 

[racerone]

Working on a customers boat is not the same concept as someone doing their own work.