Reply
 
Thread Tools Search this Thread
 
Old 07 July 2015, 17:44   #1
Member
 
Country: UK - Scotland
Town: Haddington
Make: Avon SR4
Length: 4m +
Engine: 50 Hp
Join Date: Apr 2015
Posts: 47
SR4 30 Knots

Well had a good day at North Berwick on Sunday . First run in calm waters gps was reading 30 knots with my 50 on the back and rev sitting at 6k could have went more but my sensible head kicked in..............

Looks like I have the RIB BUG!!!
__________________

__________________
Lee40 is offline   Reply With Quote
Old 07 July 2015, 17:58   #2
Member
 
Country: UK - England
Town: Royal Wootton Bassett
Length: 8m +
Engine: 250
Join Date: Jul 2008
Posts: 8,020
SR4 30 Knots

Your under propped, you should hit 33-36 with a 50
__________________

__________________
whisper is offline   Reply With Quote
Old 08 July 2015, 03:03   #3
Member
 
SimonStDavids's Avatar
 
Country: UK - Wales
Town: St Davids
Boat name: Mellifera
Make: Avon
Length: 4m +
Engine: Outboard
Join Date: May 2010
Posts: 169
RIBase
Quote:
Originally Posted by whisper View Post
Your under propped, you should hit 33-36 with a 50

+1

If you are hitting 6000 rpm with throttle to spare get a prop with more pitch. What is on there at the moment?

I have a 15" on mine and see about 35 knots flat out.
__________________
SimonStDavids is offline   Reply With Quote
Old 08 July 2015, 03:31   #4
Member
 
Country: UK - England
Town: Bristol
Make: Ribcraft
Length: 5m +
Engine: Yamaha
Join Date: May 2006
Posts: 4,194
Thats duff info. with the right balance and prop you should be able to achieve 39
I had a 10.5 x 15 four bladed spitfire prop on mine and 39.4 was its best on slack water. Aj hits 34.5 with his 40 two stroke again with the same design prop!
__________________
Member of S.A.B.S. West Country Division
matt h is offline   Reply With Quote
Old 08 July 2015, 04:21   #5
AJ.
RIBnet supporter
 
AJ.'s Avatar
 
Country: UK - England
Town: Warwickshire
Boat name: Impulse
Make: Ribcraft
Length: 5m +
Engine: Suzuki 140
Join Date: Sep 2011
Posts: 1,020
35 actually😉


Sent from my iPhone using RIB Net
__________________
AJ. is offline   Reply With Quote
Old 08 July 2015, 04:55   #6
Member
 
Country: UK - England
Boat name: Son of a Beach
Make: Avon SR4
Length: 4m +
Engine: Mercury 50hp
Join Date: Sep 2012
Posts: 130
Since I've had my carbs cleaned out and my Mercury 50 is running well I also get 6k indicated on my rev counter. However given that when the engine is off it indicates ~1k rpm I'm unsure whether the rev counter is reading well. Waiting for some calm water to do some top speed testing. I'll also have a poke about to see what the fitted prop is and how this compares to the spare that came with the boat.
__________________
Tim in Yorkshire is offline   Reply With Quote
Old 08 July 2015, 05:09   #7
Member
 
Country: UK - England
Town: Bristol
Make: Ribcraft
Length: 5m +
Engine: Yamaha
Join Date: May 2006
Posts: 4,194
Quote:
Originally Posted by AJ. View Post
35 actually😉


Sent from my iPhone using RIB Net
Nobber!!
__________________
matt h is offline   Reply With Quote
Old 08 July 2015, 13:08   #8
RIBnet admin team
 
Poly's Avatar
 
Country: UK - Scotland
Boat name: imposter
Make: FunYak
Length: 3m +
Engine: 2 stroke YAM 20 HP
MMSI: 235089819
Join Date: Sep 2005
Posts: 10,114
Tim, it is common for tach to show the rpm when the engine was turned off. If you have a key turning to on (but not as far as start) will normally reset it.
__________________
Poly is offline   Reply With Quote
Old 08 July 2015, 13:44   #9
Member
 
Country: UK - England
Town: Mighty Penryn
Boat name: Little Joe.
Make: Avon Searider
Length: 4m +
Engine: Honda BF50
Join Date: Aug 2005
Posts: 8,841
Don't prop for top speed, that's hairy chest medallion wearing shit. Any tosser can put the throttle on the end-stop on a flat calm day and take pics of the GPS.
Real men prop for grunt. Our's will do 32knts WOT with a 14 3/8 s/s prop. It leaps onto the plane and is as punchy as ferk in any kind of sea.
__________________
Mollers is offline   Reply With Quote
Old 08 July 2015, 14:03   #10
Member
 
Country: UK - Scotland
Town: Haddington
Make: Avon SR4
Length: 4m +
Engine: 50 Hp
Join Date: Apr 2015
Posts: 47
Cheers Guys ..

Think I will leave the prop on for the now, seems to pull okay with 2 people plus an auxiliary motor as well.
Only upgrade looking to do is fit BOAT BACK REST STAINLESS STEEL NEW Backrest seat back handle ideal for RIB BR1 | eBay

Thanks again for all the wise words.
__________________

__________________
Lee40 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 23:40.


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