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Old 10 April 2008, 08:18   #1
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impeller change

Hi

How often should an impeller be changed ?. Would you change it based on the number of hours done or after a period of time or combination of both ?.

Thanks
Tim
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Old 10 April 2008, 10:13   #2
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Hi

How often should an impeller be changed ?. Would you change it based on the number of hours done or after a period of time or combination of both ?.

Thanks
Tim
Some engine manufacturers recommends a change evey 100/150 hours use, others yearly, but in reality will depend on the amount of water pressure seen on the exiting port, if it's poor or hesitates change, don't go longer, will overheat yor engine. Other issue will be a matter of cost, if the work is done in a shop, do it yourself if you were a mechanic. Impellers are cheap $ 15-30 depending on the model.

Happy Boating
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Old 10 April 2008, 17:35   #3
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Impellor xhange

As mentioned wach for dropoff in water pressure. Ifboat is being used in sandy estury there will be more wear on the impellor.

After two three years all lower units should be dropped and the top of the drive shaft greased where it slots into the crankshaft. Failure to do this can result in the two bonding together with serious consequences. See other recent posts of difficulty of removing lower legs that have got siezed.

Best of luck.

rgds
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Old 10 April 2008, 18:25   #4
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[QUOTE=Ezgoing;244949] As mentioned wach for dropoff in water pressure. If boat is being used in sandy estury there will be more wear on the impellor.

If normal engines are being used in sandy stuaries, muddy rivers & lakes the impeller and water pump case (cylinder) will wear out fast compared to sea use, in that case change for a chrome plated & reinforced impeller kit. Ask your store/dealer for them.

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Old 11 April 2008, 20:29   #5
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Mine is 8 years old and on the original impeller, I know of another RIB here that is 1995 age and still on original impellers on both engines (Mariner 75 2/ IIRC). I got a lot of "attitude" from some folks here that mine was going to pack up as soon as I left the harbour because the impeller was knackered, well 2 years later it is still going, still has a strong telltale and no sign of problems. I probably ought to change it but if it ain't broke...!

Probably going to be a bugger to get off when I do need to though...
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Old 12 April 2008, 08:15   #6
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I probably ought to change
Thats a good idea, you wouldn't want any of the little bits of rubber breaking off and disappearing into the water galleries in the powerhead, that would a really nasty job stripping it down to find them.

Pete
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Old 12 April 2008, 11:10   #7
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Quote:
Mine is 8 years old and on the original impeller, I know of another RIB here that is 1995 age and still on original impellers on both engines (Mariner 75 2/ IIRC). I got a lot of "attitude" from some folks here that mine was going to pack up as soon as I left the harbour because the impeller was knackered, well 2 years later it is still going, still has a strong telltale and no sign of problems. I probably ought to change it but if it ain't broke...!
I change mine every year as a matter of course. An impeller only costs £15 and it's piece of mind when it's been done.

Sod's Law dictates that if it's going to fail - you'll probably be 5 miles offshore in a force 5/6 as it's getting dark.

Good opportunity to inspect the water pump, grease the drive-shaft, etc.

Use a rubber mallet to free lower end if it's refusing to budge.
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Old 12 April 2008, 13:33   #8
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Experience has shown me that failure is gradual and results in low water pressure which can activate the overheat alarm at progressively lower speeds.

Last time I changed mine I did the base plate and housing along with the gasket as well as the impeller. The kit for my engine retails at around £95.
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Old 12 April 2008, 13:48   #9
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Quote:
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Experience has shown me that failure is gradual and results in low water pressure which can activate the overheat alarm at progressively lower speeds.

Last time I changed mine I did the base plate and housing along with the gasket as well as the impeller. The kit for my engine retails at around £95.
This failure mode has been confirmed by my Merc. guy. The rubber blades of the impeller take a set over time and the problem may only show up at lower rpm. Every two years is suggested.
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Old 12 April 2008, 16:52   #10
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The problem may only show up at lower rpm.
That's actually the opposite of what I experienced... first alarm happened a top speed, then progressively lower speeds until we limped home at little more than tickover. I reckon every two years more than often enough for a leisure outboard.
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