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Author Topic:   Water Pump Impeller: Replacement--How Often
jimh posted 10-07-2005 12:06 AM ET (US)   Profile for jimh   Send Email to jimh  
Please contribute anecdotal data about how often you replace your water pump impeller--the rubber gizmo in the engine lower unit.

I changed the impeller on my 1992 Evinrude V6 225-HP in the Spring of 2004. Thus I have two seasons of use on it, and I don't plan to change it this fall. I'll go into next season with it, unless I notice anything unusual on the water pressure gauge or in the aspirator water output stream.

How many seasons do you get on your impeller?

PeteB88 posted 10-07-2005 12:13 AM ET (US)     Profile for PeteB88  Send Email to PeteB88     
My hard core friends change every year. SEDOC manuals suggest frequent changes as part of preventive maintenance - I can't recall exactly how often. I learned to do my own, it's not bad at all. I haven't done it on my Yamaha yet and will do in Spring when my buddies do theirs. We'll call it the Impeller Party.
LHG posted 10-07-2005 12:22 AM ET (US)     Profile for LHG    
I keep hearing stories, like JimG's Yamaha 150, which went 10 years on the impeller, fresh water use only, and when it was replaced, the mechanic said it didn't need it!

I think generally, the recommendation is about every two or three years, at least in salt conditions, as long as the hours aren't excessive. This is mostly to avoid "set" which weakens the flow. In salt, you want a strong flow to keep the deposits from building up in the water passages.

rtk posted 10-07-2005 12:31 AM ET (US)     Profile for rtk  Send Email to rtk     
Funny you mention this subject. I just spoke to a dealer today about a purchase I am about to make. The motor is a 1976 Johnson 85 horsepower. He noticed a possible leak in the lower unit, he was going to drop it to investigate the leak.

I asked him if he thought it would be prudent to change the water pump while he had it off. I said I'd pay for the parts and labor, I didn't even expect him to fix a leaky lower unit.

He said they really don't change the water pump assemblies very often, he has not seen a need to change them as frequently as many do. They pretty much keep an eye on the cooling function, and replace as needed. They typically don't wear out- they get damaged from picking up sand and other stuff. Keep it clean and they will last a good long time.

They were not very excited about taking my money to do the job. They will replace it if there is a sign of malfuntion or damage. If it looks good, no worries.

I bet you we have some Yacht club boats used for the sailing program that have never had the water pump serviced, going on six or so seasons now. They have not overheated.


Buckda posted 10-07-2005 09:56 AM ET (US)     Profile for Buckda  Send Email to Buckda     
Three years.

But hey, I change my auto oil every 3,000 miles too...

DillonBW posted 10-07-2005 10:06 AM ET (US)     Profile for DillonBW  Send Email to DillonBW     
Every three years, but this year it has not changed the fact my 60 Johnson is STILL seting off the overheat warning.
I'm getting pretty good at dropping the lower unit now.
Ha bloody ha!

New E-tec is beginning to look reeeeel nice....

WHALER27CC posted 10-07-2005 10:07 AM ET (US)     Profile for WHALER27CC  Send Email to WHALER27CC     
I would recommend every other year at the very LEAST.It certainly is not worth the risk that you take by skipping it, because its one of the main components that if ignored for too long , can destroy your entire engine.
There is one other consideration here thats worth mentioning here. Its very important to lower the lower unit down yearly, if for no other reason,but to grease the spline shaft to prevent it from freezing inside the powerhead.
I had a Merc 45hp that was in mint condition , except the lower unit hadnt been brought down in several years , causing the lower unit to become frozen on permanantly. After trying EVERYTHING that the folks at Mercury, and my mechanic tried unsuccessfully to unfreeze it,I was forced to replace the motor.

Overheating and water pumps are just simply, not the only considerations here.....

alfa posted 10-07-2005 10:41 AM ET (US)     Profile for alfa  Send Email to alfa     
Best practice is to replace every two years.
Just preventive maintenance to avoid overheating in salt water use.
Just my 0.02


GP posted 10-07-2005 12:06 PM ET (US)     Profile for GP  Send Email to GP     
What does this cost? I just purchased a 72 Nauset with an 86 Johnson. The overheat alarm went off running up the ICW, and I can't be certain that the impeller has ever been replaced.


Maximus posted 10-07-2005 12:33 PM ET (US)     Profile for Maximus  Send Email to Maximus     
Good and timely topic...

I had the impeller and water pump housing changed on my 2003 90 HP Mercury 4 stroke after three years and 100+ hours of saltwater use and it didn't need it.

The impeller looked great, no small cracks cracks or tears. The wear plate did show contact, but no measurable wear.

Based upon this go-around, I will probably wait until I hit 400-500 hours before replacing it again.

What was surprising is the amount of salt build up in the housing. The parts were literally white with salt deposits. I flush with muffs and freshwater after each use. The obvious build up of salt really makes me question the usefullness of flushing. Any comments?

Tom W Clark posted 10-07-2005 12:44 PM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
The former owner of my boat had the water pump kits done every year. When I asked my mechanic about the need for this on Mercury outboards (I had never done this on my Johnsons) he sad that was excessive. He suggested once every three years or so for recreationally used boats.

I never replaced the impeller on my 1979 Johnson 70 over the two years I owned it.

I never replaced the impeller on my 1982 Johnson 90 which I only owned for one year.

I never replaced the impeller on my 1986 Johnson 90 over the four years I owned it.

I never replaced the impeller on my 1990 Johnson 150 over the ten years I owned it.

I've replaced the impeller several times on my 1974 Johnson 6 and twice now on my 1987 Johnson 9.9.

None of these motors ever showed signs of weak water circulation.

I replaced the impeller on my 1965 OMC sterndrive after it had been sitting in a barn unused for at least 12 years. The impeller on this one did not look worn at all but it was stiff, with a set to it. After replacing the impeller the motor clearly did circulate water more effectively.

RocketMan posted 10-07-2005 03:57 PM ET (US)     Profile for RocketMan  Send Email to RocketMan     
I have replaced the (neoprene?) impeller in a 90 Yamaha every 2-3 years for 20 years with no problem and suspect that non-use causes more performance loss than regular recreational use.

It seems that as long as the boat is being used regularly the removed impeller blades display an even, relatively small amount of equally distributed curl. If the boat has sat for any extended period of time it seems that there are one or two blades that have a little more curl than the others and that the telltale is weaker.

daverdla posted 10-07-2005 04:39 PM ET (US)     Profile for daverdla  Send Email to daverdla     
1989 Montauk with 1992 Evinrude 100XP - I replace the impeller every two years - I'm sure I got that advice from this website. I've been advised to follow the two year rule for raw water pumps on my diesels in my other boat.
Sonic posted 10-07-2005 05:03 PM ET (US)     Profile for Sonic  Send Email to Sonic     
I got a new Tohatsu TLDI 90 on the montauk this year, replacing a Johnson 90. Tohatsu seems to be adament in replacing the impeller EVERY YEAR and even notes that even if you use it very little, that it should be replaced. I thinK i replaced the water pump once in 10 years on the Johnson.

Anyway, with the new motor being under warranty, I'm going to follow their suggestion (and do it myself to save labor cost), but once it is out of warranty, I think every 2 years should be fine with the ~100 hours of use it gets.

82 Montauk 17, 05 T

djahncke posted 10-07-2005 05:04 PM ET (US)     Profile for djahncke  Send Email to djahncke     

I had been feeling a little uneasy about the impeller in the 1978 70hp Evinrude on my 15 Sport for a few years since I had never replaced it since I bought the motor new in January 1979. When I bought it I lived in Florida so it saw salt and brackish water for its first year of use, although I flushed the motor religiously after every use and I did not store the boat in the water.

Anyway, this August I went to use the boat and there was no telltale (this motor has always had a good strong telltale). I shut the motor down immediately and used my 17 Dauntless to tow the boat to ramp, got it on its trailer and hauled it to see Jerry my friendly Evinrude dealer in Cheboygan. I didn't want to attempt this one on my own since the lower unit hadn't been opened up since the factory put it together 27 years ago. Once, Jerry opened the motor he found that the impeller was in very good shape. The problem was some sand sucked up into the water pump (those of you that have been to my cottage know how shallow it is around my dock). We cleaned out the sand and replaced the impeller since we already had the water pump disassembled.

So, I got 26 years of use out my impeller and would have gotten more had it not been for some sand.

swist posted 10-07-2005 05:49 PM ET (US)     Profile for swist  Send Email to swist     
It is indeed sand and silt that are the determining factor - an impeller which ingests sand becomes an orbital sander!

If you are sure you have not been near the bottom, there is probably little point in changing the impeller, but not many of us have that luxury.

Personally I do think that 2 years is a little compulsive (unless you know you are in brackish conditions). I've always done 3-5 years on many different outboards and they never looked like I needed to do it...

ConB posted 10-07-2005 06:33 PM ET (US)     Profile for ConB  Send Email to ConB     
My 1982 Evinrude 15 h.p. has never had the impeller changed. It's used in clean fresh water. I'm thinking my Johnson 150 h.p. should have the impeller changed more often being there is more at stake.
Over the LINE posted 10-07-2005 07:21 PM ET (US)     Profile for Over the LINE  Send Email to Over the LINE     
I change the impeller on my 50hp Yamaha every year, after duck season ends. I do it because the motor spends all winter running mud through the cooling system. If it was not for the abuse, I would probally go two or three years between changes.

As a refernce point, I have a garage full of boats parts that are too good to throw away but not good enough to be in regular use. So I guess I am a little crazy when it comes to maintenance.

SpeedBump posted 10-07-2005 08:59 PM ET (US)     Profile for SpeedBump  Send Email to SpeedBump     
When I acquired my Nauset it had a 3 year old nissan 70hp on it w/reportedly very low hours, less than 50. Like the tohatsu noted above the manual recommends changing the impeller every year. As a precaution I had a Nissan service center replace the impeller and go over the engine for adjustments.

The impeller that had been removed looked brand new. the impeller casing was not changed as there were no wear marks.

I have used this for three seasons now and do plan on changing it this coming spring during its spring fitting out. I will also change the thermostate as is now reccommended by many.

I ran my 40 hp Yamaha for 6 years w/o a change of pump impeller or thermostat, it always had a strong teltale. I also ran a Johnson 7.5 longshaft seahorse for 15 years w/o a change of impeller but did replace the thermostat once.

When this discussion comes up with both Sea-Tow and Boat-US tow operators in my boating area they always recommend replacement of impellers every year. Apparently failed cooling systems is the major use of their tow insurance. Since they don't do maintenance services they have nothing to gain if people do follow their recomendations except good will for giving good advice.

Another bit of good advice is if your boat is laid up for three months or more for winter do not change the impeller in the fall at lay up time unless you are willing to go out to the boat and turn the flywheel by hand on a monthly basis. Apparently turning the fly wheel avoids getting a stagnant set in the impeller that adds to premature failure. Therefore it is best to wait for spring, this all sounds logical to me.

Depending on the condition of my current impeller that will get replaced in March '06 after three full years of use, I'll determine the schedule of future replacements after comparing it to the one pulled three years ago.

frontier posted 10-07-2005 09:46 PM ET (US)     Profile for frontier  Send Email to frontier     
The 1st Whaler we ever had (and the only one I ever bought new) was a 1972 13' Sourpuss with a 1972 402 Merc (40 HP). Never replaced the impeller in 15 years of ownership. Looked and ran like new the day we bought it and the day we sold it.
davej14 posted 10-09-2005 10:51 AM ET (US)     Profile for davej14  Send Email to davej14     
The owners manual for my year 2000 75 merc 2-stroke recommends replacing the impeller every three years. I replaced it at the three year point and you couldn't tell the difference between the old one and the new one. FYI, I run in fresh water only. I will probably wait 5 or 6 years before the next replacement and keep a eye on the tell tale. I think it cost me about $70.00 including the cost of the impeller.
russellbailey posted 10-10-2005 02:20 PM ET (US)     Profile for russellbailey  Send Email to russellbailey     
1987 Evinrude 70 on a 1980 Striper 15. Estimate 500 hrs of use.

Impeller 1 - 1987-mid 2002 - freshwater only
- no problems when replaced - preventative only
Impeller 2 - mid 2002-late 2004 - salt&fresh
- mechanic said he could see some corrosion on
mounting bolts, but ok
Impeller 3 - late 2004 - ?? - salt&fresh

Based on my experience, I'll probably replace #3 in late 2006 since it has been used in saltwater.

If I was using it in only freshwater, I think I'd go at least 5 years, maybe 10.

prm1177 posted 10-10-2005 05:36 PM ET (US)     Profile for prm1177  Send Email to prm1177     
Every year. It's part of the pre-season maintenance: 1) Impeller, 2) Lower unit service, 3) new plugs, and 4)check the wiring and fuel lines.
Buckda posted 10-10-2005 05:51 PM ET (US)     Profile for Buckda  Send Email to Buckda     
Interesting point, above - re: replacing impeller in spring rather than fall.

PRM1177's post above drove that home when I checked his location. He does the lower unit in the spring, but in the Midwest where we get hard freezes for MONTHS at a time, we generally recommend lower unit service in the FALL so that any water that may be in there is flushed out and fresh lube is in the gear casing.

Changing the impeller in the spring makes a lot of sense from the perspective of not having the impeller get "set" in a certain position, however it is somewhat impractical for the boaters who do their annual service in the fall before winter lay-up.

I guess if you had your mechanic perform these services, it would make sense to have the impeller changed in the spring when they are "de-winterizing" your engine.

I still go with the every three years recommendation - but then again, that is in fresh-water only. Saltwater use would prompt me to consider a more aggressive schedule (on all aspects of boat maintenance).


Peter posted 10-10-2005 06:44 PM ET (US)     Profile for Peter  Send Email to Peter     
I follow a three year routine in the saltwater. Never had a problem with that.

Only water pump problem I've had was on the Evinrude 35 and that was simply because the pump had never been changed over 10 years and the engine spent most of its life at 5500 RPM. Those were the days. ;)

17 bodega posted 10-10-2005 09:03 PM ET (US)     Profile for 17 bodega  Send Email to 17 bodega     
I had mine done this year because I thought the tell tale sign was weakened... the old one was a bit worn, but the tell tale did not improve.

My story is short and sweet.. I will observe the tell tale and wait until it weakens further befure replacing again... by the way I watched and can now do it myself...
pretty easy.

where2 posted 10-10-2005 10:11 PM ET (US)     Profile for where2  Send Email to where2     
1985 70Hp Johnson, Purchased used in 1996. I replaced the impeller for the first time during my ownership in May of 2004. I had no evidence of necessity to replace the pump. I simply decided that 7+ years was probably long enough.

The engine sees 99.8% salt water use, and the impeller was still quite serviceable according to the mechanic who disassembled it in front of me after I brought him the lower unit.

As for the various manufacturers and their "Annual" replacement schedule. I once took my own poll of the manufacturer's service technicians at the Miami International Boat Show (Mercury, OMC, and Yamaha), asking the question: Why do you recommend annual replacement of the water pump impeller, and why do you not use (or recommend) anti-seize on the lower unit bolts?

The answer was generally: By recommending annual impeller replacement, we feel that the bolts should not need anti-seize, and you will replace the impeller before it becomes defective. You may be able to get more than one years service out of an impeller. However, the bolts may become problematic if not removed annually.

mag posted 10-11-2005 10:29 AM ET (US)     Profile for mag  Send Email to mag     
I replaced it three years ago on my '79 175HP Johnson. Still appears to be working fine, but will replace it again soon.
Don88outrage posted 10-11-2005 11:38 AM ET (US)     Profile for Don88outrage  Send Email to Don88outrage     
Maintenance on most jet engines today is either scheduled or
whats called indicated maintenance. Indicated maintenance is based on systems that detect problems prior to failures.
I used to be paranoid about water pumps and spent too much time and $$ on cooling systems that I now consider an indicated maintenance item, probably due to the fact that the first outboards we had didn't have the types of flow indicators todays outboards have. Include a good engine temperature gauge and let the systems tell you when it's time to replace a pump or thermostats.
Joe 15 SS LTD posted 10-15-2005 12:20 PM ET (US)     Profile for Joe 15 SS LTD  Send Email to Joe 15 SS LTD     
On my 70 hp 1989 merc. I have replaced impeller once at 9 years and it was used in saltwater mostly.It has now been six years and impeller is still pumping fine but now is mostly a freshwater boat.When impeller was changed at 9 years it still looked good, no wear visible.
Joe Kriz posted 10-15-2005 05:53 PM ET (US)     Profile for Joe Kriz  Send Email to Joe Kriz     
I purchased a new 1985 Evinrude 70hp with VRO in 1888... New Old Stock...

I ran the engine in both fresh and salt water for 15 years.

I NEVER changed the water pump or impeller on this engine.

It always had the strongest tell tale of any engine I have ever had including engines that I had changed the impeller on...

I sold the boat and engine a couple of years ago... The only thing I ever did to that engine was replace the prop seal, other than the spark plugs of course...

I believe the hardest impact on the water impeller is if the engine sits for a considerable length of time and allows the rubber impeller fins to dry out and crack from lack of use.

pglein posted 10-17-2005 11:54 AM ET (US)     Profile for pglein  Send Email to pglein     
I had been running outboards for 20 years and never even knew they had rubber impellers. I always assumed they were metal, like cars. That is, until this summer when one failed and seized my motor.

Now, I'd say replace it every year, just as you would on a marine inboard diesel.

RMS posted 10-20-2005 01:40 PM ET (US)     Profile for RMS  Send Email to RMS     
I usually change them every 5 seasons (6 months usage in salt). One thing I do when winterizing is turn the flywheel backwards (with plugs removed). The logic is that any 'set' of the pump vanes from winter storage is mitigatated by summer usage.
runpasthefence posted 11-21-2005 01:41 AM ET (US)     Profile for runpasthefence  Send Email to runpasthefence     
Every season, maybe more if necessary - I run in all salt, and I'm usually in very sandy conditions. It is common for me to bump the skeg on the sandy bottom of Morris Island (sand bar area) when beaching usually each weekend. It is here and the relatively shallow tidal creek that I pick up most of my sand/sediment. Because of this, I flush the motor after every use, regardless of what happens while I'm out.

I work when I can at a marine maintenance shop. I'm not certified, so that limits me to water pumps, services, steering, well everything minus major rebuilds and diagnosis. We see a lot of water pump jobs, and the majority need it. It's not uncommon for me to find substantial amounts of sand/mud/oyster shell bits stuffed into the housings. Charleston's surrounding waterways prove confusing to some people I guess. When these things get around the impeller, they cut grooves into the housing resulting in lost pressure. Also, it's common to find impellers with cracked blades, sometimes to the point to where they've broken off. Stay out of the sand, if you can't, replace your impeller every 2 years

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