Cavitation issue with new Solas prop.

Fenlander · 30 August 2011, 09:53

Just before our hols bought a new Solas prop for our Mariner 15 2-stroke. Despite being the correct replacement it looked a little different but the supplier assured me "they are all like that now". Fitted it and carried old (decent condition) prop as a spare in case any Scottish rocks were encountered.

On the first trip out our Zodiac 360 Fastroller (correctly up to pressure) really didn't want to plane with the prop cavitating. When it was finally nursed onto the plane it would cavitate and drop off the plane very easily.

Fiddled about with outboard trim and weight distribution but no real improvement.

So wondered about the prop and swapped the original one back on.... problem sorted.

Looking at the two props side by side the Solas seems to have a larger blade area of a different shape. Most noticeable is that the Mariner prop blade leading root rises smoothly from the boss at a shallow angle but the Solas is almost a right angle.

Note: Solas on the right.

By fenlander2 at 2011-08-30

By fenlander2 at 2011-08-30

To my amateur eye the Solas looks more like a displacement design. Anyone experienced similar problems?

willk · 30 August 2011, 10:34

It does have a certain Hi-thrust gimp about it...

I wonder is it one of those "optimised for 4 stroke" jobs?

Fenlander · 30 August 2011, 10:46

>>>I wonder is it one of those "optimised for 4 stroke" jobs?

Yep... effectively that's what it says on the box and why I double checked with the supplier before fitting causing them to use the phrase "that's how they all are now".

Erin · 30 August 2011, 10:48

I presume you mean 'ventilating' where it is drawing air down from the surface and losing grip. Is it the same diameter? Also, is the AVP on the outboard flush with the bottom edge of the transom?

Fenlander · 30 August 2011, 11:24

I don't know if it was cavitating or ventilating but I do know it was slipping. The old Mariner prop was a 9" and the Solas a 9.25"... the slight diameter increase was also "how they are supplied now".

Sorry to show ignorance but is the AVM the anti-cavitation plate? Assuming so it's 1.75" below the transom.

Erin · 30 August 2011, 11:46

Technically it's an anti ventilation plate to stop surface air being drawn down and entrained around the prop causing slip. Cavitation is where the pressure aginst the water causes it to 'boil' and turn to gas also causing slip and after a while pitting damage to the surface of the prop. I wonder if the extra diameter isn't part of the problem.

willk · 30 August 2011, 12:02

Just out of curiosity, is the pitch the same on both?

Hightower · 30 August 2011, 12:04

Another area to look at is the fit of the "skirt" part of the prop and the gearbox rebate that it fits in. If the gap is too big the exhaust gases will flow out the gap and right over the surface of the blades causing ventilation.

Fenlander · 31 August 2011, 08:58

Yes the pitch on both is the same. I do wonder about the exhaust gas isssue though. The Solas prop boss is a good fit inside the gearhousing but internally where the exhaust gas flows the casting is quite crude whereas the original Mariner one has been designed for good gas flow with all internal edges nicely rounded.

Anyway the supplier, while reluctant to accept there is anything wrong with the Solas design, has agreed to exchange for an OE one if I stand the cost of sending the Solas back. I'm happy with that.

Hightower · 31 August 2011, 09:18

Quote:

Originally Posted by Fenlander

Yes the pitch on both is the same. I do wonder about the exhaust gas isssue though. The Solas prop boss is a good fit inside the gearhousing but internally where the exhaust gas flows the casting is quite crude whereas the original Mariner one has been designed for good gas flow with all internal edges nicely rounded.

Anyway the supplier, while reluctant to accept there is anything wrong with the Solas design, has agreed to exchange for an OE one if I stand the cost of sending the Solas back. I'm happy with that.

I'd call that a result then.

Out of interest, did the supplier recommend the Solas as a replacement or did you choose it on the grounds of cost?

willk · 31 August 2011, 10:05

Yes, a result. I was considering an Amita replacement for the toohotsue (previous owner had a few close encounters). They look suspiciously like the solas version. Might just pay the money and have done with it. Or send it to SteelDev this winter.

Fenlander · 31 August 2011, 12:23

The supplier offers a refurb or a new Solas on their website, not noticed an OE replacement option and I'd presumed that would be expensive so didn't even ask. The last Solas I had about three years ago for my Mariner 20 was identical to the original prop.

You mention an Amita Willk... well on the box this one I have is called a Solas Amita 3.

As a matter of interest am I the only person who carries a spare prop and tools to change?

jyasaki · 31 August 2011, 15:45

Quote:

Originally Posted by Fenlander

As a matter of interest am I the only person who carries a spare prop and tools to change?

Nope.

jky

Hightower · 31 August 2011, 17:32

As a matter of interest am I the only person who carries a spare prop and tools to change?

Nope!

Fenlander · 09 September 2011, 09:29

I just wondered as not many SIB owners I've talked to do carry a spare.

Anyway a genuine Mercury prop has arrived as a no-charge replacement today. Identical to the original so I know it'll be fine.

Thanks to Steel Developments for a quibble free service. I don't doubt I was the first complaint they've had of this kind hence their initial puzzlement but I know many say an air-floor SIB can be prone to performance/slip problems and seemingly the Solas prop just tipped my setup into these issues.

willk · 09 September 2011, 09:57

Quote:

Originally Posted by Fenlander

I just wondered as not many SIB owners I've talked to do carry a spare.

At 2.7m, mine is just too small. On a bigger boat, rigged for coast hopping, I'd bolt one to the transom - although I think they're a potential injury hazard, so maybe in a bow box like Prairietubers

Good to get the full story of the solas prop. Saved me a lot of trouble, maybe. Thanks!