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Old 24 October 2012, 09:59   #11
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Leapey I chased after a chatter problem when I had a Tohatsu 90 TLDI and changed the prop to a Solas Myth 3 Blade Alu. It would behave exactly as you described and sounded awful when you were in forward or reverse gear with hardly any revs.

I went through shift cables adjust, spline washers, torque settings, the lot trying to solve it only to find out it was that particular prop. Seems several diff Solas models have this issue (don't think just Solas) because when I put a diff prop on it went immediately.
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Old 24 October 2012, 13:09   #12
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Quote:
Originally Posted by npm108
Leapey I chased after a chatter problem when I had a Tohatsu 90 TLDI and changed the prop to a Solas Myth 3 Blade Alu. It would behave exactly as you described ...
Unless someone can convince me otherwise I'm happy it's simply unloaded/lightly loaded gear chatter (resonance) caused by the different mass of the Solas SS prop.

In cars, there's considerable time and money spent eliminating this gear chatter and it wasn't always successful. Mini A series idler gear rattle is infamous as was the manual gearbox Jaguar S Type. It's less common with modern dual mass flywheels.

I seriously doubt, given the number of different Solas props, that they've run and tested every variant for every engine and then fine tuned bush rates to attenuate it out.

Done over 100 miles now since fitting the Solas prop, over 20 at WOT. It's got no better and no worse and I don't forsee any long term problems as it's purely a light load or no load condition.
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Old 26 October 2012, 02:39   #13
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Any thoughts though why you get gear chatter with some props and not others? Are they off-balance or do you think it's a design issue with that particular prop.

I ran for a whole season with my noisy prop and it was only when I came to sell that boat that the buyer pointed out the noise and wanted it sorted out.
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Old 26 October 2012, 04:16   #14
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Quote:
Originally Posted by npm108
Any thoughts though why you get gear chatter with some props and not others? Are they off-balance or do you think it's a design issue with that particular prop.

I ran for a whole season with my noisy prop and it was only when I came to sell that boat that the buyer pointed out the noise and wanted it sorted out.
I can only think it's a weight issue - a SS prop is considerably heavier than an ali one. The engine OEM designs a complete powerhead to prop system and tunes the prop bush to attenuate any gear rattle. As I said earlier, there's no way Solas or any other replacement prop supplier could does this for every prop/engine combination they make.

It's definitely not a balance issue - if it was, the rattle would more likely be vibration that would get worse with increasing revs.

How did you "sort it" for a potential buyer?
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Old 26 October 2012, 14:27   #15
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I think it comes down to play in the gears. The alloy prop is lighter, so can follow the shaft as it speeds up and slows down as the motor lumps along near idle. The SS prop has more mass, so tends to maintain rpm, so the gears absorb the rpm differences, and what you hear is the backlash in the rest of the drive train.

As I said, I think this is the cause.

jky
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Old 26 October 2012, 14:59   #16
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I think it comes down to play in the gears. The alloy prop is lighter, so can follow the shaft as it speeds up and slows down as the motor lumps along near idle. The SS prop has more mass, so tends to maintain rpm, so the gears absorb the rpm differences, and what you hear is the backlash in the rest of the drive train.

As I said, I think this is the cause.

jky
Certainly another possibility that amounts to the same thing ... float or slack or backlash in the gears causes unloaded/lightly loaded gear chatter. No big deal ...
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