That old Change your impeller every year debate

[smallribber]

Got my Brothers boat ready for him to go boating in. He does nothing to it and I don't think he has started it in over a year. He/We have owned the boat over 6 years and it has never had a new impeller. Not sure how long the one in it had been in before we bought the boat.

I Charged the battery and it started after about 4 attempts. Petrol in tank very old.

It seems to run ok and pumps water like a trojan .

https://www.youtube.com/watch?v=sqck0FSX2wQ

Makes you think !

[The Gurnard]

I am no expert Big Plumbs but would imagine the impeller is like everything..if you dont use the boat much..it will last for years. I do my own servicing and check my impellers every winter but only replace them when I think they require replacing.

Example my 6HP Yamaha Four stroke averages around 200 hours per year. I check the impeller every winter and decided to change it after three years of use..approx 600 hours of running. It was still in reasonable conditions but the ends of the blades were wearing flat and it was starting to loose its spring feeling when I bent them..if that makes sense.

So yes..you are correct they could be fine..but if it was my OB ..I would at least check their condition. Simply because if they fail at sea..(and you have no idea what shape they are in ?) ..they could cause a loss of life. If not yours or your brothers ..someone elses if the RNLI are attending to your problem and someone else gets into serious trouble. Admittedly .. very unlikely .. but not something I could live with if it happened to me .. simply because I ignored checking a vital part of the engine that does wear out.

Does my reply make you think ?

PS..I don't replace my plugs every year either..I keep them going until I think they are done..but I check them regular too ..and carry a spare set on the boat

[gpsguru]

Originally Posted by Bigplumbs

Makes you think !

Certainly, modern merc 4 strokes are impellor change every 3 years or every 300 hours and TBH I have never changed an impeller as part of an annual service, but I do inspect it every year ............

At 6 years you really need to have a good inspection for the rubber cracking at the root of the vanes ...........

[ShinyShoe]

Originally Posted by Bigplumbs

It seems to run ok and pumps water like a trojan .

Makes you think !

I'm thinking:

- why would someone think it would have failed in storage.
- how long will it be till a vein tears off and stops pumping properly.
- when a vein tears off will little bits of the rubber break off and block up the water channels
- if it was as simple as failing when testing in a tank rather than underway then people wouldn't replace routinely

[smallribber]

Answers below in red

Originally Posted by ShinyShoe

I'm thinking:

- why would someone think it would have failed in storage. They think the Rubber holds its bent position
- how long will it be till a vein tears off and stops pumping properly. Who Knows
- when a vein tears off will little bits of the rubber break off and block up the water channels Could do like all the other rubbish that is sucked into the raw water intake
- if it was as simple as failing when testing in a tank rather than underway then people wouldn't replace routinely Many don't replace routinely

[smallribber]

Originally Posted by The Gurnard

I am no expert Big Plumbs but would imagine the impeller is like everything..if you dont use the boat much..it will last for years. I do my own servicing and check my impellers every winter but only replace them when I think they require replacing.

Example my 6HP Yamaha Four stroke averages around 200 hours per year. I check the impeller every winter and decided to change it after three years of use..approx 600 hours of running. It was still in reasonable conditions but the ends of the blades were wearing flat and it was starting to loose its spring feeling when I bent them..if that makes sense.

So yes..you are correct they could be fine..but if it was my OB ..I would at least check their condition. Simply because if they fail at sea..(and you have no idea what shape they are in ?) ..they could cause a loss of life. If not yours or your brothers ..someone elses if the RNLI are attending to your problem and someone else gets into serious trouble. Admittedly .. very unlikely .. but not something I could live with if it happened to me .. simply because I ignored checking a vital part of the engine that does wear out.

Does my reply make you think ?

PS..I don't replace my plugs every year either..I keep them going until I think they are done..but I check them regular too ..and carry a spare set on the boat

Very wise words. I wonder however about the old adage if it ain't broke don't fix it


Or as I have herd it...... if it ain't broke don't break it

[ShinyShoe]

Originally Posted by Bigplumbs

Very wise words. I wonder however about the old adage if it ain't broke don't fix it


Or as I have herd it...... if it ain't broke don't break it

Do you change oil in your car?
What about timing belts?

[Fenlander]

I'm always a bit nervous with any used new to me outboard re the impeller condition even if it pumps OK so as part of getting the outboard to a known position I'll change it using a genuine OE one. With the Yamaha 15 2-stroke I bought this year I put in the full kit with upper pump housing liner and lower plate so it starts off as new.

Now I've done this, with our low leisure use hours compared to Gurnard, I'll probably only drop the lower unit 2 yearly and replace the impeller then whatever the condition. For me it's not worth the trouble of just inspecting at such an interval but then leaving the old one in.

[Poly]

Originally Posted by gpsguru

At 6 years you really need to have a good inspection for the rubber cracking at the root of the vanes ...........

If those leg bolts have been sitting for over 6 years I’d be keen to check they will actually move when needed.

BP presumably your inlet has a “grill” on it to filter out the big bits that won’t make it through the passages. There is no guarantee the bits that break off will be small enough to cause you no problem.

FWIW - I don’t religiously change impellers annually. I actually think many people don’t. But with an engine of that age having been sitting doing nothing for a long time - I wonder why you would take the risk.

[smallribber]

Originally Posted by Poly

If those leg bolts have been sitting for over 6 years I’d be keen to check they will actually move when needed.

BP presumably your inlet has a “grill” on it to filter out the big bits that won’t make it through the passages. There is no guarantee the bits that break off will be small enough to cause you no problem.

FWIW - I don’t religiously change impellers annually. I actually think many people don’t. But with an engine of that age having been sitting doing nothing for a long time - I wonder why you would take the risk.

Because it is pumping water very well and changing it is unnecessary.

Why would you do something that does not need doing why would you take the risk of messing something up when you pull it to pieces. Always a risk

There is theory and then their is facts and the evidence you see

If you have 10 boats + to look after and 12 engines you tend to only do what is necessary

[Bushrider]

I installed on all my outboards water pressure gauges .
Gave me during the year additional piece of mind .

[smallribber]

Originally Posted by Bushrider

I installed on all my outboards water pressure gauges .
Gave me during the year additional piece of mind .

Now that is interesting where do you install those.... Any pictures

[Fenlander]

>>>Why would you do something that does not need doing why would you take the risk of messing something up when you pull it to pieces.

>>>If those leg bolts have been sitting for over 6 years I’d be keen to check they will actually move when needed.


Yep that's the worry I'd consider BP... getting the lower unit off if it's been in place several years. Two problems... the lower unit bolts Poly mentions are inclined to snap off which is a whole world of pain and even worse the driveshaft splines can seize in the powerhead causing folks to employ all sorts of inventive but risky methods such as suspending the outboard upside down by the lower unit and hammering down on the underside of the power head.

This master bodger hammer jockey shows just how stuck they can get...

https://www.youtube.com/watch?v=-ka2A3RdGZ0

[Fender]

Originally Posted by Bigplumbs

Because it is pumping water very well and changing it is unnecessary.

Why would you do something that does not need doing why would you take the risk of messing something up when you pull it to pieces. Always a risk

There is theory and then their is facts and the evidence you see

If you have 10 boats + to look after and 12 engines you tend to only do what is necessary

The engine manufactures schedule for impeller replacement is where I'd start and personally I always err on the side of caution

[smallribber]

Originally Posted by Fender

The engine manufactures schedule for impeller replacement is where I'd start and personally I always err on the side of caution

So ignoring reality and following that old Myth then.

[GuyC]

Fender - don't rise to it.

[Fender]

Originally Posted by GuyC

Fender - don't rise to it.

lol, I've said my piece
Whatever people choose to do on the water is ultimately their prerogative, whether or not its the right thing is another matter

[Dan Gurney]

Originally Posted by Bigplumbs

So ignoring reality and following that old Myth then.

What myth is that? The myth of preemptive maintenance?

To be honest I think the original premis of this post has value... particularly with reference to the 'old fuel' debate. Though even on that topic I'm not sure that the fact it runs in a bucket means that it will run well under load; personally I'd top it up with as much fresh as I could.

On the subject of preemptive maintenance, I would like to add my voice to the 'pro' side. The idea that you would just wait for something as crucial as an impeller to fail and not even check it is borderline irresponsible. And once you've got to the stage of checking it then for the relatively low cost of the part then you may as well replace it.

To be honest I find much of what the OP posts on rib.net to be inexplicable, inconsistent, and often wilfully contrarian. For someone with such a self-professed breadth and depth of knowledge on all types of motors, from remote control aircraft to ion drives and beyond, to have such a cavalier attitude to maintenance doesnt seem to me to quite ring true. But that is merely an opinion. He evidently takes great delight in proving people/manufacturers 'wrong' and exploding the 'myth' of duty lifecycles for engine parts; and if you share that passion the fill your boots. Just try not to stray too far from shore cos someone else will have to come and get you.

[Dan Gurney]

Originally Posted by Fender

lol, I've said my piece
Whatever people choose to do on the water is ultimately their prerogative, whether or not its the right thing is another matter

Which is why I think it's important for other people to said their piece on these threads. Many folk new to boating use these boards as a reference (I did/do) so I think it's useful to highlight the fact that Mr Plumbs doesn't necessarily represent 'the orthodoxy' in all matters.

[beamishken]

Originally Posted by Bigplumbs

Because it is pumping water very well and changing it is unnecessary.

How do you know it isnt necessary it could be ready to disintegrate any time?

Why would you do something that does not need doing why would you take the risk of messing something up when you pull it to pieces. Always a risk

If your that unsure of your abilities perhaps you should trust the work to someone more competent! Stripping the lower unit off regularly prevents it from siezing on and ensures you can fix it when you need to

There is theory and then their is facts and the evidence you see

If you have 10 boats + to look after and 12 engines you tend to only do what is necessary

Perhaps you should thin down your fleet so you can properly maintan what you have