Reply
 
Thread Tools Search this Thread
 
Old 30 November 2008, 07:24   #1
Member
 
Country: UK - England
Town: ash
Boat name: aquaplane
Make: humber assault 5.5
Length: 5m +
Engine: opti 115
Join Date: Nov 2008
Posts: 21
mercury 115 opti prop selection

my opti 115 is now all run in and running fine.on w.o.t. max revs are 5250, on looking at mercurys specs for this model it states max rpm at wot should be 5000-5750. i am happy with acceleration /top speed/fuel economy, is there any point in me experimenting with props to achieve 5750 at wot.i am just concernd for engine longevity/ reliability.
__________________

__________________
seafreak is offline   Reply With Quote
Old 30 November 2008, 07:43   #2
RIBnet admin team
 
Nos4r2's Avatar
 
Country: UK - England
Town: The wilds of Wiltshire
Boat name: WhiteNoise/Dominator
Make: Ballistic 7.8/SR5.4
Length: 7m +
Engine: Opti 225/Yam 85
MMSI: 235090687/235055163
Join Date: Jul 2005
Posts: 12,645
RIBase
Quote:
Originally Posted by seafreak View Post
my opti 115 is now all run in and running fine.on w.o.t. max revs are 5250, on looking at mercurys specs for this model it states max rpm at wot should be 5000-5750. i am happy with acceleration /top speed/fuel economy, is there any point in me experimenting with props to achieve 5750 at wot.i am just concernd for engine longevity/ reliability.
What's the load onboard when you get 5250rpm?
You probably won't go any faster if you get 5750 at WOT-but you'll use more fuel. I might be tempted to go down 2" if I was getting 5250rpm with a light load though as it'll be straining a bit with a load onboard.
__________________
Need spares,consoles,consumables,hire,training or even a new boat?

Please click HERE and HERE and support our Trade Members.

Join up as a Trade member or Supporter HERE
Nos4r2 is offline   Reply With Quote
Old 30 November 2008, 07:49   #3
Member
 
Country: UK - England
Town: ash
Boat name: aquaplane
Make: humber assault 5.5
Length: 5m +
Engine: opti 115
Join Date: Nov 2008
Posts: 21
hi, load was usual for my boat; 75ltrs fuel 3 adults and 2 med size kids
__________________
seafreak is offline   Reply With Quote
Old 30 November 2008, 07:51   #4
Member
 
Hightower's Avatar
 
Country: UK - England
Town: Fareham
Length: 6m +
Join Date: Sep 2003
Posts: 7,855
If you're happy as you've stated, then stick to the lower revs as it'll give you the best MPG. Going for a higher RPM WOT might well give you better top speed (although not always) with improve acceleration, however your fuel consumption with go up and might well be dissapointed with the results against spending all that money on a new prop.

If you want to experiment then I would recommend having a look at the prop thread and seeing if anyone would lend you a prop just to trial.

http://rib.net/forum/showthread.php?t=22455
__________________
Andy

Looks Slow but is Fast
Member of the ebay Blue RIB cover club.
Hightower is offline   Reply With Quote
Old 30 November 2008, 07:58   #5
Member
 
Country: UK - England
Town: ash
Boat name: aquaplane
Make: humber assault 5.5
Length: 5m +
Engine: opti 115
Join Date: Nov 2008
Posts: 21
thankyou hightower.
__________________
seafreak is offline   Reply With Quote
Old 30 November 2008, 08:04   #6
RIBnet admin team
 
Nos4r2's Avatar
 
Country: UK - England
Town: The wilds of Wiltshire
Boat name: WhiteNoise/Dominator
Make: Ballistic 7.8/SR5.4
Length: 7m +
Engine: Opti 225/Yam 85
MMSI: 235090687/235055163
Join Date: Jul 2005
Posts: 12,645
RIBase
I'd stick with what you've got too-that's quite a big load for a 5.5m boat anyway so you'll prob rev quite a bit more lightly loaded.
__________________
Need spares,consoles,consumables,hire,training or even a new boat?

Please click HERE and HERE and support our Trade Members.

Join up as a Trade member or Supporter HERE
Nos4r2 is offline   Reply With Quote
Old 30 November 2008, 15:14   #7
RIBnet supporter
 
Country: UK - England
Town: South Coast
Length: 7m +
Join Date: Apr 2008
Posts: 1,445
I have 5.7m Rib with the Mariner Opti 115.

With 4/5 adults, which is my usual loading, I get around 5200rpm and about 35-36kts.
However, with just 2 aboard, she will pull 5600+rpm and get 42kts. This is with the standard ali prop.
The biggest issue is the leading edge of the prop. If it has the slightest dink and therefore blunt edge, the rpm can drop on WOT. Take a bit of time to clean it up and a dab of paint and away she goes. I average about 1.3miles/ltr at around 30kts
Hope this helps
Steve
__________________
250kts 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 19:54.


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