Propellor maintenance / cleaning

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Airscrew
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Propellor maintenance / cleaning

Post by Airscrew »

Hi all,

We have had our Centaur only a few weeks.
It has been very well maintained, but has been sitting in the water on the Hamble unused for nearly 12 months.
I have access to a hard, tidal, washing/scrubbing berth, and will examine and powerwash the hull in the next week or two, and have a good general look around below the waterline.

A couple of days ago, coming back up the Hamble, against the tide, the motor would not pull more than 2000rpm. I had only normally used 1500/1800 before, in 'normal' up/down river pottering. Progress was slow.
No doubt there was drag from some hull fouling. But I don't expect too much as the hull had osmosis and CU-coating 6 years ago.

The engine (MD11c but recently overhauled) has been well looked after and is in good condition.
Therefore I suspect there may/will also be some contamination of/on the propeller.
No idea (yet) wether it is a 2 or 3 blade prop, but almost certainly original.

Q.
In a standard engine/prop centaur, should I expect to see more than 2000rpm under load. I was expecting 2300 or so.
Q.
If there is a build-up on the prop, and I anticipate barnacles, should I wire brush, by hand or with power tool, or apply chemical (spray and wash-off). If so, what product? (ie Starbright from MarineStore??)
Q.
If I need to, and do clean the prop, should I leave it bare or Vaseline coat it, or something else?
Q.
Anything also to look out for while I have the chance? (The keel bolts have been strengthened and are bone dry.)

NB...
I will only have 3-4 hours at low tide, so options are tide limited.


Thanks for any hints and tips.
Jonathan.
Westerly CR1826 Centaur 'ForFive' based Hamble
Gary-Cottam
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Re: Propellor maintenance / cleaning

Post by Gary-Cottam »

Hi,

Congratulations on the Centaur!

My MD2B would achieve 2300, but I guess it depends on many factors including prop size, and as you say condition etc.

I cleaned teh prop with a battery grinder and one of these blue pads:

Image

Image

I didn't coat mine with anything and was fine after 1 season.
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Haven Marina, Ipswich
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Re: Propellor maintenance / cleaning

Post by Airscrew »

Thanks for the reply. That's a dramatic difference.

I don't recognise the pad/disc. Is it wire wool?
It looks impregnated with the 'blue' material. Does it have a name/brand?

Thanks and Best.
J.
Westerly CR1826 Centaur 'ForFive' based Hamble
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Re: Propellor maintenance / cleaning

Post by Gary-Cottam »

Try an Ebay search for '4" poly disk'
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Re: Propellor maintenance / cleaning

Post by TyroSailor »

Is yours an MD2b or MD11B? They're not the same, although similar I believe. (There was a thread on this a year or so ago).

2400 is the nominal maximum revs for the MD2b, whereat it's claimed to develop its full quota of 25 horses, but calculations show (I've recently discovered) that 11hp is enough to move a 3.5ton 26' boat at its hull speed of 6 knots. This is borne out by my delivery trip from Langstone to Southampton, when I ran it at about 1300 rpm most of the way (almost no wind) and managed about 4 - 5kn.

Since then, however, it's given up, and is due to be replaced by a Vetus M2.18 (16hp) when my engineer extracts his digit.

If you only have a few hours, I should think moderate abrasion as recommended above is the way to go. It will make a big difference, as will cleaning off any weed on the hull. And barnacles, if you have time.
Experience: That which would have been most useful five minutes before you acquired it.

Steve
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Re: Propellor maintenance / cleaning

Post by Airscrew »

TyroSailor wrote:Is yours an MD2b or MD11B? They're not the same, although similar I believe. (There was a thread on this a year or so ago).

2400 is the nominal maximum revs for the MD2b, whereat it's claimed to develop its full quota of 25 horses, but calculations show (I've recently discovered) that 11hp is enough to move a 3.5ton 26' boat at its hull speed of 6 knots. This is borne out by my delivery trip from Langstone to Southampton, when I ran it at about 1300 rpm most of the way (almost no wind) and managed about 4 - 5kn.

Since then, however, it's given up, and is due to be replaced by a Vetus M2.18 (16hp) when my engineer extracts his digit.

If you only have a few hours, I should think moderate abrasion as recommended above is the way to go. It will make a big difference, as will cleaning off any weed on the hull. And barnacles, if you have time.
MD11C.
But I take your point that they deliver enough power to reach max hull speed without needing full revs.
So I will move ahead wit the hull and prop cleaning.
Thanks Tyro.
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Re: Propellor maintenance / cleaning

Post by Airscrew »

Gary-Cottam wrote:Try an Ebay search for '4" poly disk'
Great. Thanks.
I see Toolstation and Screwfix both have something similar.
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Re: Propellor maintenance / cleaning

Post by Konsortium »

Hi,

A friend of mine, polished my brass three bladed prop with a standard wire brush attachment and an angle grinder. I presume it wasn't done aggressively but it looks amazing and has lasted well.
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Re: Propellor maintenance / cleaning

Post by aquaplane »

If all your seacocks move no need to do much with those. The Blakes ones on the bog may appreciate a little grease but you can do that with a dry hull and wet keels so it doesn't eat into your dry time. Google is your friend for instructions on how to look after them.

Have an anode ready just in case you need it, you will eventually and it won't go to waste. It will actually but that's its job :) They are only £20 or so with the foam backing and new nuts.

Get your wellies on and scrub the hull while there is water round the boat, it's easier than using a bucket.

Antifouling paint only sticks to a dry hull, a hull rinsed with fresh water dries faster than a salty one.

When drying out at Tobermory, there is time to do the distillery tour while the hull dries before you do the antifouling.

I lost about a knot with weed wrapped around my prop, I can't remember how the revs were affected though, probably not much IIRC.

I tend not to run at 2000rpm for long as the engine gets over warm, 1800rpm it'll run all day. There is a thread about MD11C overheating and improving water flow somewhere on here.
Bob.
Centaur now sold. Boating from Tarbert.
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