Reply
 
Thread Tools Search this Thread
 
Old 20 October 2014, 19:05   #1
Member
 
m22nly's Avatar
 
Country: UK - England
Town: Taunton
Make: Ring 650
Length: 6m +
Engine: Outboard
Join Date: Jul 2014
Posts: 110
Prop cavitation

Hi I have just bought a ring 6.50 rib with a mariner 90 four stroke. The bow seems to be a bit low in the water but if I try to trim up it cavitates very easily it is running on a 15 pitch aluminium prop was wondering if increasing the pitch may stop the cavitation and make it possible to lift the bow on trimming rather than cavitating any ideas welcome


Sent from my iPad using RIB Net
__________________
m22nly is offline   Reply With Quote
Old 20 October 2014, 19:23   #2
Member
 
Country: UK - England
Town: Bristol
Make: Ribcraft
Length: 5m +
Engine: Yamaha
Join Date: May 2006
Posts: 4,299
15 pitch seems a little on the low side. What size prop??
I would hazard a guess at 13 x 17 ...!
Need to look at trim cavitation plate on the out board. ideally half an inch above V on hull
which links in to engine height so could be too high.
I'm also thinking engine a bit light for that hull. i personally don't know that hull at all but the engine comes in at 155kgs i think..
Check the engine cav plate fisrt. Maybe post a pic of the rear
__________________
Member of S.A.B.S. West Country Division
matt h is offline   Reply With Quote
Old 20 October 2014, 19:43   #3
Member
 
m22nly's Avatar
 
Country: UK - England
Town: Taunton
Make: Ring 650
Length: 6m +
Engine: Outboard
Join Date: Jul 2014
Posts: 110
I think the engine height is pretty much right between 1/2" to an inch max but will check at the weekend and get a pic if I can. I think 15" pitch is low aswell but talking to the broker I bought from he thinks a 17" would cure the cavitation but I was thinking 19" maybe. I need to get the boat back out and see what it is revving at at full throttle with a bit of grin I guess.


Sent from my iPad using RIB Net
__________________
m22nly is offline   Reply With Quote
Old 21 October 2014, 13:46   #4
Member
 
m22nly's Avatar
 
Country: UK - England
Town: Taunton
Make: Ring 650
Length: 6m +
Engine: Outboard
Join Date: Jul 2014
Posts: 110
Click image for larger version

Name:	ImageUploadedByRIB Net1413899018.537934.jpg
Views:	240
Size:	37.4 KB
ID:	100123
I have put a straight edge on the cavitation plate so as you can see the height. The prop number is 48 77342A45 15p not sure what diameter it is . Anyone know what a good stainless option would be to give better bow lift ?? Or anyone have a stainless prop available for this motor ??


Sent from my iPad using RIB Net
__________________
m22nly is offline   Reply With Quote
Old 21 October 2014, 13:55   #5
Member
 
Johnscubanut's Avatar
 
Country: UK - England
Town: Beds/South coast
Make: Ribcraft 585
Length: 6m +
Engine: Yam 115
Join Date: Jul 2010
Posts: 294
That engine looks a bit high to me? Any chance of dropping it lower on the transom? We run a 15 inch pitch but have to haul heavy divers & kit out to dive sites. A 17 pitch would be ok though, but I still think you should try to lower the engine. Regards-John
__________________
Johnscubanut is offline   Reply With Quote
Old 21 October 2014, 14:01   #6
Member
 
m22nly's Avatar
 
Country: UK - England
Town: Taunton
Make: Ring 650
Length: 6m +
Engine: Outboard
Join Date: Jul 2014
Posts: 110
The engine would go down one hole on the transom Brkt but any lower would need new holes drilling in the transom which I don't fancy . Would one hole make much difference ??


Sent from my iPad using RIB Net
__________________
m22nly is offline   Reply With Quote
Old 21 October 2014, 14:43   #7
Member
 
Country: UK - Scotland
Make: Destroyer 5.5/Ring18
Length: 3m +
Engine: Yam 90HP/Yam200HP
Join Date: Jul 2009
Posts: 958
I have a Ring 18 with a 200 HP 2 stroke on it, I have my engine up as high as it will go, the cavitation plate is roughly 3" above the bottom of the hull, it sits great in the water at all speeds.
__________________
69cmw is offline   Reply With Quote
Old 21 October 2014, 17:34   #8
Member
 
Country: UK - England
Town: Retford
Boat name: Spy-sea-one
Make: Excel 435
Length: 4m +
Engine: Suzuki Outboard/25/4
Join Date: Oct 2011
Posts: 7,441
RIBase
I run a Suzuki 90 four stroke with Ali 14x19 s/s 13.5x 21 and a s/s 14x20 all work well the 14x20 drops the revs by approx 500revs

Regards Jeff
__________________
jeffstevens763@g is offline   Reply With Quote
Old 21 October 2014, 21:08   #9
Member
 
Oscarguitar's Avatar
 
Country: UK - England
Town: Poole
Boat name: Half Cut
Make: Cobra 8.6
Length: 8m +
Engine: Verado 275
MMSI: 235104619
Join Date: Jun 2011
Posts: 381
The 1" above the transom stuff is a good guide but read this article as well.

Propping correctly & how to test props.....
__________________
Oscarguitar is offline   Reply With Quote
Old 21 October 2014, 23:53   #10
Member
 
dave3235's Avatar
 
Country: UK - England
Town: Bristol
Boat name: Salty Cheeks
Make: Honwave
Length: 3m +
Engine: 20hp 2stroke Mariner
Join Date: Mar 2014
Posts: 485
Quote:
Originally Posted by Oscarguitar View Post
The 1" above the transom stuff is a good guide but read this article as well.

[url=http://www.veradoclub.com/smf/index.php?topic=137.0]Propping correctly & how to test props.....[
/url]
Hi all.

I saw this awhile ago and thought it was very informative and logical mmm that sweet spot.
__________________
dave3235 is offline   Reply With Quote
Old 22 October 2014, 06:05   #11
Member
 
m22nly's Avatar
 
Country: UK - England
Town: Taunton
Make: Ring 650
Length: 6m +
Engine: Outboard
Join Date: Jul 2014
Posts: 110
Just read that article probably the best advice yet I will try that at the weekend and go from there . Many thanks


Sent from my iPad using RIB Net
__________________
m22nly 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




All times are GMT. The time now is 06:38.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2024, vBulletin Solutions, Inc.