Reply
 
Thread Tools Search this Thread
 
Old 05 September 2011, 13:26   #1
Member
 
kubcat's Avatar
 
Country: Australia
Town: Sydney
Boat name: Lunasea
Make: Ribtec 890SX
Length: 8m +
Engine: Yamaha ME 421STI x 2
Join Date: Aug 2009
Posts: 475
Does anyone recognise this SIB?

Took out our SIB for the second time and was a little disappointed at the performance with an older 15hp. It didn't seem that fast and was wondering if I should get the short shaft motor higher as there was lots of spray.

This boat planed with a 3.5 on it's first outing a year ago.

It has an inflatable keel and floor which I had at about 8psi. The tubes were at 3.5psi as per the compliance plate. I seem to recall that the floor and tubes should be 11psi but have lost the manual.

Amy suggestions?
Attached Thumbnails
Click image for larger version

Name:	image-926245879.jpg
Views:	279
Size:	64.2 KB
ID:	62406  
__________________
kubcat is offline   Reply With Quote
Old 05 September 2011, 15:52   #2
Member
 
Country: UK - England
Town: Calne, Wiltshire
Boat name: Shot Away
Make: BWM DeepSea 21
Length: 6m +
Engine: Mercury BlackMax 200
Join Date: May 2011
Posts: 40
If there was a lot of spray, shouldn't you lower the motor? Maybe I missed something, sorry!
__________________
Don't worry, this is perfectly normal. Could someone pass me the flares please?
Calne Diver is offline   Reply With Quote
Old 05 September 2011, 17:39   #3
Member
 
Country: UK - England
Town: gravesend
Boat name: curach/Earl
Make: seago/Lifeguard 4M
Length: under 3m
Engine: 3.3 marinar/10 hp
Join Date: Jul 2008
Posts: 802
Most sibs are short shaft designed,sounds like you may have had the leg at an angle?if it planed with a 3.5 ,very small hp?,would of thought you would of got on the plane with a 15hp,my 10hp get's my heavy 4m on the plane no prob
__________________
thornbackflound is offline   Reply With Quote
Old 05 September 2011, 22:07   #4
Member
 
kubcat's Avatar
 
Country: Australia
Town: Sydney
Boat name: Lunasea
Make: Ribtec 890SX
Length: 8m +
Engine: Yamaha ME 421STI x 2
Join Date: Aug 2009
Posts: 475
No problem getting on the plane, just wasn't a Lot faster. Maybe I am expecting too much.

I tried different trim settings and can't go down with the engine so thought I might try up till it cavitates. Probably makes more sense to go down buy that is not an option.

I think the problem is more likely to be not enough air pressure but don't know how high to go on the floor and keel.
__________________
kubcat is offline   Reply With Quote
Old 05 September 2011, 23:40   #5
Member
 
Country: UK - England
Town: gravesend
Boat name: curach/Earl
Make: seago/Lifeguard 4M
Length: under 3m
Engine: 3.3 marinar/10 hp
Join Date: Jul 2008
Posts: 802
Quote:
Originally Posted by kubcat View Post
No problem getting on the plane, just wasn't a Lot faster. Maybe I am expecting too much.

I tried different trim settings and can't go down with the engine so thought I might try up till it cavitates. Probably makes more sense to go down buy that is not an option.

I think the problem is more likely to be not enough air pressure but don't know how high to go on the floor and keel.
I might try up till it cavitates. Not to good for the engine,shakes the hell out of the gear box
__________________
thornbackflound is offline   Reply With Quote
Old 06 September 2011, 08:45   #6
Member
 
Pete7's Avatar
 
Country: UK - England
Town: Gosport
Boat name: April Lass
Make: Moody 31
Length: 9m +
Join Date: Aug 2001
Posts: 4,951
The sib colour schemes and square bow make it look like a Suzuki often sold under their Suzumar label.

Pete
__________________
.
Ribnet is best viewed on a computer of some sort
Pete7 is offline   Reply With Quote
Old 06 September 2011, 08:49   #7
Member
 
Pete7's Avatar
 
Country: UK - England
Town: Gosport
Boat name: April Lass
Make: Moody 31
Length: 9m +
Join Date: Aug 2001
Posts: 4,951
Next thought is you may have too much weight at the stern? Shift the seat to the middle position. You might need one of those aftermarket tiller extentions to reach but an old broom and some gaffer tape would do to confirm the problem first.

Pete
__________________
.
Ribnet is best viewed on a computer of some sort
Pete7 is offline   Reply With Quote
Old 06 September 2011, 17:06   #8
Administrator
 
John Kennett's Avatar
 
Country: UK - England
Town: Brighton
Length: 3m +
Join Date: May 2000
Posts: 7,108
Quote:
Originally Posted by kubcat
I think the problem is more likely to be not air pressure but don't know how high to go on the floor and keel.
If you're not sure then the floor is almost certainly not inflated enough. Get that sorted first before you muck about with the engine.

Floor should be something like 10psi which is a lot more than you think it is. Keel doesn't need so much, but does need more than the tubes. Perhaps someone with a similar boat like a Quicksilver airdeck could see what their book says.
__________________
John Kennett is offline   Reply With Quote
Old 06 September 2011, 17:56   #9
RIBnet admin team
 
Fenlander's Avatar
 
Country: UK - England
Town: Cambridgeshire
Boat name: Nimrod II
Make: Aerotec 380
Length: 3m +
Engine: Yam 15 Tohatsu 9.8
Join Date: Nov 2007
Posts: 8,881
I'd go for 10psi in the floor as in this Quicksilver manual...

http://www.mercurymarine.com/media/m...-899194001.pdf

It is unthinkable that performance would be similar between a 3.5hp and 15hp... something very wrong here.
__________________
Fenlander is offline   Reply With Quote
Old 06 September 2011, 18:40   #10
Administrator
 
John Kennett's Avatar
 
Country: UK - England
Town: Brighton
Length: 3m +
Join Date: May 2000
Posts: 7,108
Quote:
Originally Posted by Fenlander
It is unthinkable that performance would be similar between a 3.5hp and 15hp... something very wrong here.
Agreed, but let's make sure the boat is set up right first. A floppy floor will lead to prop ventilation and lousy performance whatever the motor.
__________________
John Kennett is offline   Reply With Quote
Reply


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 23:16.


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