Impeller life in outboard motor

[philipp10]

Originally Posted By: InhalingBullets
IMHO impeller failures are from a lack of use and temperature changes while stored. We change every 2 years, but when we are out we are 20+ miles away from where we launch. That is a LOOONg expensive tow.


"temperature changes while stored"....why? I don't see where temperature would play a role.

 

[svchareta]

One advantage I have found when replacing impellers on a regular basis is that the screws that hold the impeller housing in place do not corrode together due to galvanic corrosion between two different metals, ie stainless steel screws and an aluminum housing and motor lower unit. When the screws are removed during impeller replacement and anti-seize is applied on a regular basis impeller replacement is quite easy. Many screws are broken or threads stripped on motors that have not had their impellers replaced after very long periods

 

[dblshock]

just replaced my oem impeller, 1986 Classic Fifty Mercury.

 

[claluja]

Originally Posted By: Donald
Two years normal use or 2 seconds without water.


Sounds about right. I just replaced mine after 1 year and 240 hours. The impellers were still in good shape after 240 hours which was last time I replaced them. But I had no accidental dry starts in that time, and used regularly. As stated above, put light grease on interior of housing and use anti-seize for bolts especially if in saltwater. If you have an accidental dry start, I'd check or replace them soon.

 

[FranklinJL]

Originally Posted By: 4WD
Did not find much in search, so here goes:
Looking for real world feedback on impeller change - some say hours - some say based on time saying it has a "memory" - said differently - they will loose restoration force over time.
I am running low hours - flush both ways - and have pump pressure guage ...


I have a skeeter 20i w/250 yamaha....impeller change is easy, I do it every 2 years, or say every 100 hours

 

[BrocLuno]

Low hours over two years means it sits in one position for extended periods of time. If the polymer is going to take a set, that's the way to do it.

Change every 2~3 years because it is also good to get a real close look at the lower unit seals and that's easier up on the bench than laying on the ground behind the boat ... Easy to change the fluid too

 

[Bluestream]

Got back back from local deal (bought an impeller) I asked how long they last, he said his outboard is 12 years old with the original. Rotate the flywheel every few months and they dont develop a set.

 

[JTK]

Originally Posted By: Bluestream
Got back back from local deal (bought an impeller) I asked how long they last, he said his outboard is 12 years old with the original. Rotate the flywheel every few months and they dont develop a set.


That's a great idea for smaller outboards for sure! Move it monthly even.

For I/O's with the pickup pump in the outdrive, you're kind of stuck. Ugh.. No pun intended.

 

[claluja]

FWIW, I've had 3 impellers fail in inboards around the 3 year mark.

 

[Tman220]

Unless I missed it... What is the application that we are talking about, brand of engine, size, outboard or I/O, what kind of water its used in (clear, turbid, sand, salt, etc)

In my experience many of the older OMC engines had very robust impeller setups and would last a surprising amount of time if used in clean water, and not run dry. I picked up a 1975 Johnson 9.9 a couple years ago that I thought ran slightly hot at WOT, I decided to check the impeller and it was quite obvious by the untouched paint on the bolts on the lower unit and the impeller and housing that it was original, 40 years old and still pumping well enough to not fry the engine. About 20 years ago I picked up a 1966 Evinrude 6 hp, I still own it and use it every year, has always pumped good water so I have never bothered changing the impeller. My family has a 1995 Evinrude 30 hp on a pontoon that's never been changed and still cools fine. Last spring I changed the original impeller on my dads 1997 60 HP Yamaha and it was still in great shape, usually used about 60-70 hours a year. I could keep going on.

On the opposite side of the spectrum some of the earlier Mercury engines really liked to have fresh impellers every year, especially on the inline 6 cylinder (tower of power) since once water pressure started to go down with a slightly deformed impeller would cause the upper cylinder to get hot.

I think a lot of it has to do with the robustness and capacity the OEM decided to build into the water pump design. According to the shop manual on my dad's 60 HP yamaha as long as you can maintain 11 psi of water pressure and high rpm's the impeller is in fine shape. I know on some of the mid range to high end OMC's 20+ PSI is pretty common on a new impeller.

 

[claluja]

Originally Posted By: Tman220
Unless I missed it... What is the application that we are talking about, brand of engine, size, outboard or I/O, what kind of water its used in (clear, turbid, sand, salt, etc)

In my experience many of the older OMC engines had very robust impeller setups and would last a surprising amount of time if used in clean water, and not run dry. I picked up a 1975 Johnson 9.9 a couple years ago that I thought ran slightly hot at WOT, I decided to check the impeller and it was quite obvious by the untouched paint on the bolts on the lower unit and the impeller and housing that it was original, 40 years old and still pumping well enough to not fry the engine. About 20 years ago I picked up a 1966 Evinrude 6 hp, I still own it and use it every year, has always pumped good water so I have never bothered changing the impeller. My family has a 1995 Evinrude 30 hp on a pontoon that's never been changed and still cools fine. Last spring I changed the original impeller on my dads 1997 60 HP Yamaha and it was still in great shape, usually used about 60-70 hours a year. I could keep going on.

On the opposite side of the spectrum some of the earlier Mercury engines really liked to have fresh impellers every year, especially on the inline 6 cylinder (tower of power) since once water pressure started to go down with a slightly deformed impeller would cause the upper cylinder to get hot.

I think a lot of it has to do with the robustness and capacity the OEM decided to build into the water pump design. According to the shop manual on my dad's 60 HP yamaha as long as you can maintain 11 psi of water pressure and high rpm's the impeller is in fine shape. I know on some of the mid range to high end OMC's 20+ PSI is pretty common on a new impeller.


Think OP has Yamaha outboards. My Yamaha manual says replace/inspect every 100 hours. Assume he's asking since they can probably go a little longer than that if no dry starts and regular use.

 

[claluja]

Originally Posted By: claluja
Think OP has Yamaha outboards. My Yamaha manual says replace/inspect every 100 hours. Assume he's asking since they can probably go a little longer than that if no dry starts and regular use.


To clarify, one of my Yamaha manuals says to inspect every 100 hrs and replace if needed, and to replace every 300 hrs regardless, and another says to replace every 100 hrs. I'm in the 200-300 hrs replacement camp, mainly because of the numerous inboard impeller failures I've had (although my Yamaha impellers have always been in decent shape when I've replaced them).

 

[Bluestream]

Changed the 10 year old impeller on my Mariner for peace of mind. The old impeller had developed a "set" on one or two of the vanes. Sat on my work bench for 3 days and they all returned to normal.

 

[4WD]

Good info. With my OptiMax - tossed the old one in a Pelican box of misc rainy day stuff - and it came back straight ...
Think the Yamaha statement based on hours is logical and the restoration force debate is likely legacy of old school material as pointed out by BL ... Think it helps to have a pump pressure guage too ... (My Yamaha does) ...

 

[The motor guy]

It's getting time to change mine out. I think it's been 4 years probably and starting to get hot a low speeds. Although once you run it at speed it seems to stabilize, but still running hotter than usual for this time of year.

 

[Silverado12]

I had a 1994 Evinrude 48 in a boat that I sold w/original impeller in 2010. I had the boat since new. My Merc Alpha One gets a new impeller every 3 years.

 

[Tman220]

Originally Posted By: motor_oil_madman
It's getting time to change mine out. I think it's been 4 years probably and starting to get hot a low speeds. Although once you run it at speed it seems to stabilize, but still running hotter than usual for this time of year.


Most outboards run hotter at low speed than high, most have a way of bypassing the thermostat once water pressure increases, if your concerned maybe shoot the heads and or upper cylinder with an infrared thermometer. The heads and upper cylinders should be 140-150 F at idle and then drop once the bypass opens. Most weak impellers will do the opposite of what you're describing. A weak impellers will cool fine and low speeds and heat up and high speeds

 

[Bluestream]

Originally Posted By: motor_oil_madman
It's getting time to change mine out. I think it's been 4 years probably and starting to get hot a low speeds. Although once you run it at speed it seems to stabilize, but still running hotter than usual for this time of year.


Impellers are cheap, engines are not...

 

[4WD]

Water pump pressure gauges are also cheap - not enough boats have them ...

 

[rokwldr]

Does anyone know what the water pressure should be at the telltale on a Yamaha 115 4-stroke? that is the only place I think you can check it. The water pressure gauge is pretty expensive cause I'm told you need a special adapter to go in the engine block. Anyway I'm getting about 5-6 lbs at the telltale at idle.