Fitting new SS Prop

[Leapy]

I've got a new Solas SS prop to fit to a Suzuki DF90. It comes with no fitting instructions so I'm assuming - not having done this before - that it's simply a question of removing the split pin, undoing the nut, removing the old prop, sliding the new one on, put the nut back, put the split pin back.

But ...

1. There's a thrust washer between prop and gearbox?
2. Does the nut get torqued or just finger tight to eliminate end float?

[mick]

Originally Posted by Leapy

I've got a new Solas SS prop to fit to a Suzuki DF90. It comes with no fitting instructions so I'm assuming - not having done this before - that it's simply a question of removing the split pin, undoing the nut, removing the old prop, sliding the new one on, put the nut back, put the split pin back.

But ...

1. There's a thrust washer between prop and gearbox?
2. Does the nut get torqued or just finger tight to eliminate end float?

You will see how tight when you take the old one off and lay the bits out In sequence and put plenty or grease on the shaft

[Leapy]

Fitted the new prop easy peasey after checking with Steel Developments about the nut torque (finger tight plus then wind on to first point where split pin can be fitted)

Slight but ... With the engine in forward gear (not reverse) and at idle there's a rattle that sounds like gear rattle. With the slightest whiff of throttle the rattle goes. For those of you of the right vintage it sounds just like old Mini A series idler gear rattle. It also comes and goes somewhat suggesting it's very rpm/load sensitive.

Can't check easily now as the boat is in the water and the old prop's back home - so I'm guessing somewhat here - but I recall the OE ali prop had a rubber bush twixt prop blades and hub but the Solas one doesn't??? It has a metal bush???Does this/could this account for gears resonating at idle?

Sound familiar to anyone?

[jyasaki]

Rattle is pretty common with SS props on outboards at idle speeds. I think it has to do with the weight of the prop (vs aluminum) causing lower end gear backlash.

Make sure the prop is on tight enough (may have settled in a bit on first run); other than that I don't think there's much you can do.

jky

[Leapy]

Cheers jky. I'll check the nut tightness again when out the water

[Hightower]

Originally Posted by Leapy

Cheers jky. I'll check the nut tightness again when out the water

I've replied to 1978SeaRider's other thread and only just seen this one.

Make sure the Prop isn't moving around on the shaft. I'm sure I had a Solas prop on my Merc and the thrust washer diameter needed turning down to fit snugly in the back of the prop. If it isn't fitted correctly it can cause all sorts of problems and damage.

Another area for noise is the fit between the prop and the gearbox. Rotate the prop by hand to make sure it's not rubbing and you have all round clearance.

[Leapy]

Hightower, thanks

When putting it together I'd checked all fits and gaps ... The prop snugs up to the gearbox casing in the same way the OE prop did - close, but clear. There's no rotational free play prop to output shaft and with the thrust washer and nut in place and tightened there's no axial float.

I'll recheck again when the boats out the water but I'll ring Steel Developments again today to see what they say.

[Pikey Dave]

Originally Posted by Leapy

but I recall the OE ali prop had a rubber bush twixt prop blades and hub but the Solas one doesn't??? It has a metal bush

I'm assuming there's some kind of bushing between the prop hub & the propshaft. It's not all metal to metal is it?

[Leapy]

Originally Posted by Pikey Dave

I'm assuming there's some kind of bushing between the prop hub & the propshaft. It's not all metal to metal is it?

PD ... Can't remember the detail of the Solas prop now ... The Suzuki ali OE prop has a very obvious rubber bush between blades and hub.

Going to the boat shortly, I'll look at the Solas prop (though boating may be off today ... very misty this morning in Truro :-() and see what Steel Developments say when they wake up

[Leapy]

Spoke to Steel Developments ... They confirm that the Solas prop DOES have a rubber bush twixt blades and hub and that the heavier SS prop can cause some gear chatter at idle revs.

So ... Keep Calm And Carry On

[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 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.

[Leapy]

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.

[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.

[Leapy]

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?

[jyasaki]

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

[Leapy]

Originally Posted by jyasaki

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 ...