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Old 22 March 2010, 13:26   #1
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A new prop

Just after some advice.I have have a mariner marathon 25hp that needs a new prop.Is it worth paying the extra money and getting a stainless steel for this size engine and would i notice any difference in performace.
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Old 22 March 2010, 14:58   #2
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The added performance of a stainless steel propeller is only due to the stiffer blades., so is debateable depending on what you plan to do with your boat.
all propellers offer different types of performance due to their different shapes i.e. rake, pitch, Diamiter and propeller cup. Stainless Steel propellers are expensive, very strong for longer life, more efficient due to greater strength permitting stiffer blades, and a blade design that provides less slippage and flexing. you may even find that with a aluminuim prop of the same specs the added performance will only be very slight.

Saying all this above........STAINLESS PROPS LOOK GREAT ON OUTBOARDS. SO GET ONE!

But dont leave it in view / reach of the few members of public who prefer not to pay for their possessions, mine was on its mooring 1/2 mile from shore and it still went missing.
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Old 22 March 2010, 16:10   #3
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Another interesting point to consider is that if/when you do actually touch something hard then the force/shock can be transfered to the driveline and damage the gearbox. Possibly it is a small risk but this is very unlikely to happen with the softer alu prop.

Now I don't actually have any first hand experience of this as I have only ever run alu props but just the possibility has put me off going to SS.

Perhaps if you run on well known water where you are very unlikely to touch bottom then the gain will outweigh the risk.

just some thoughts
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Old 22 March 2010, 18:22   #4
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Quote:
Originally Posted by sea_quest View Post
The added performance of a stainless steel propeller is only due to the stiffer blades.
I thought it was because stainless is stronger than aluminiuum so the blades can be made thinner and have less resistance in the water?
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Old 22 March 2010, 18:29   #5
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Quote:
Originally Posted by sea_quest View Post
The added performance of a stainless steel propeller is only due to the stiffer blades
Quote:
Originally Posted by chewy View Post
I thought it was because stainless is stronger than aluminiuum so the blades can be made thinner and have less resistance in the water?
Both apply I think
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Old 22 March 2010, 18:43   #6
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I think they do both deserve concideration but looking at the spec's between my ali prop and ss my ss is 2mm thicker on the cup end of the blade than the ali prop
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Old 22 March 2010, 18:45   #7
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my ss prop is a mercury laser 2
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Old 22 March 2010, 18:57   #8
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my ss prop is a mercury laser 2
Do you know what size? I have others (mirage plus; vengeance; revolution 4)

that may work better than laser, they're more for lightweight speed boats with lots of bow lift etc
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Old 23 March 2010, 11:44   #9
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I thought it was because stainless is stronger than aluminiuum so the blades can be made thinner and have less resistance in the water?
Stainless is also heavier, so it's harder to spin them up.

There's a whole bunch of variables that affect things going from Al to SS.

Bottom line is that you really need to try it before you decide, though that may be difficult if your chandler doesn't have a stable of test props.

jky
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Old 23 March 2010, 12:19   #10
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...and for a 25Hp is maybe a bit less likely to have one of an appropriate diameter lying around........
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