Reply
 
Thread Tools Search this Thread
 
Old 30 August 2011, 05:53   #1
Member
 
Country: UK - England
Town: East Anglia
Boat name: Nimrod II
Make: Aerotec 380
Length: 3m +
Engine: Suzuki DF20 EFI
Join Date: Nov 2007
Posts: 3,276
Cavitation issue with new Solas prop.

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?
__________________

__________________
Fenlander is offline   Reply With Quote
Old 30 August 2011, 06:34   #2
RIBnet admin team
 
willk's Avatar
 
Country: Ireland
Make: Redbay Boats
Length: 9m +
Engine: 370hp
Join Date: Feb 2008
Posts: 12,925
RIBase
It does have a certain Hi-thrust gimp about it...

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

__________________
willk is offline   Reply With Quote
Old 30 August 2011, 06:46   #3
Member
 
Country: UK - England
Town: East Anglia
Boat name: Nimrod II
Make: Aerotec 380
Length: 3m +
Engine: Suzuki DF20 EFI
Join Date: Nov 2007
Posts: 3,276
>>>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".
__________________
Fenlander is offline   Reply With Quote
Old 30 August 2011, 06:48   #4
RIBnet supporter
 
Erin's Avatar
 
Country: UK - Channel Islands
Town: A large rock
Boat name: La Frette
Make: Osprey Vipermax
Length: 6m +
Engine: 200 Suzzy
Join Date: May 2004
Posts: 2,830
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?
Erin is offline   Reply With Quote
Old 30 August 2011, 07:24   #5
Member
 
Country: UK - England
Town: East Anglia
Boat name: Nimrod II
Make: Aerotec 380
Length: 3m +
Engine: Suzuki DF20 EFI
Join Date: Nov 2007
Posts: 3,276
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.
__________________
Fenlander is offline   Reply With Quote
Old 30 August 2011, 07:46   #6
RIBnet supporter
 
Erin's Avatar
 
Country: UK - Channel Islands
Town: A large rock
Boat name: La Frette
Make: Osprey Vipermax
Length: 6m +
Engine: 200 Suzzy
Join Date: May 2004
Posts: 2,830
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.
Erin is offline   Reply With Quote
Old 30 August 2011, 08:02   #7
RIBnet admin team
 
willk's Avatar
 
Country: Ireland
Make: Redbay Boats
Length: 9m +
Engine: 370hp
Join Date: Feb 2008
Posts: 12,925
RIBase
Just out of curiosity, is the pitch the same on both?
__________________
willk is offline   Reply With Quote
Old 30 August 2011, 08:04   #8
Member
 
Hightower's Avatar
 
Country: UK - England
Town: Fareham
Length: 6m +
Join Date: Sep 2003
Posts: 7,855
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.
__________________
Andy

Looks Slow but is Fast
Member of the ebay Blue RIB cover club.
Hightower is offline   Reply With Quote
Old 31 August 2011, 04:58   #9
Member
 
Country: UK - England
Town: East Anglia
Boat name: Nimrod II
Make: Aerotec 380
Length: 3m +
Engine: Suzuki DF20 EFI
Join Date: Nov 2007
Posts: 3,276
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.
__________________
Fenlander is offline   Reply With Quote
Old 31 August 2011, 05:18   #10
Member
 
Hightower's Avatar
 
Country: UK - England
Town: Fareham
Length: 6m +
Join Date: Sep 2003
Posts: 7,855
Quote:
Originally Posted by Fenlander View Post
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?
__________________

__________________
Andy

Looks Slow but is Fast
Member of the ebay Blue RIB cover club.
Hightower is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -5. The time now is 21:47.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.