Reply
 
Thread Tools Search this Thread
 
Old 08 August 2018, 18:46   #1
Member
 
Vinny31's Avatar
 
Country: UK - N Ireland
Town: Armagh
Make: Xs
Length: 6m +
Engine: 150 optimax
Join Date: Aug 2017
Posts: 127
Time to change prop I reckon

Weíve had our 6m XS since February and on the few occasions Iíve got to use it full throttle Iíve noticed itís not reaching the recommended rev range.

Weíre running an optimax 150 of 2006 vintage and itís pulling roughly 5200 flat out, seemingly we should be pulling between 5250 and 5750 and ideally Iíd like to be towards the higher end of this as we usually run lightly loaded.

Itís currently running the prop seen below, any guidance or recommendations with regards to a replacement? Iím not so bothered about top speed, throttle response and Ďgruntí would be preferable. Click image for larger version

Name:	IMG_5002.JPG
Views:	82
Size:	268.0 KB
ID:	126307Click image for larger version

Name:	IMG_5003.JPG
Views:	85
Size:	246.4 KB
ID:	126308

Thanks
__________________

__________________
Vinny31 is offline   Reply With Quote
Old 08 August 2018, 22:19   #2
Member
 
Country: Ireland
Town: Dublin
Make: XS650
Length: no boat
Engine: Mercury 150
Join Date: Feb 2016
Posts: 217
Are you trimming out to achieve WOT?

If it’s any use to you...
We have XS650 and Merc 150 4Stroke with 19in prop.
Trimmed out we get 42 kts at 5300rpm- boat feels a little light when trimmed out and fast though.
Recently changed from aluminum to stainless prop. Top speed pretty much the same but new prop makes boat much livelier above 20kts.
I’d still like more bite in rough weather so may try 17in 4 blade.
__________________

__________________
Iron Dials is offline   Reply With Quote
Old 09 August 2018, 02:39   #3
Member
 
spartacus's Avatar
 
Country: UK - Scotland
Town: Aberdeenshire
Boat name: Sula
Make: Ribcraft 4.8m
Length: 4m +
Engine: Tohatsu 60hp + aux
MMSI: 235087213
Join Date: Jun 2007
Posts: 3,466
RIBase
Mercury Vengeance stainless steel propellers seem to to get a good write up, and importantly are available in 17 and 18" pitches. Normally drop down a pitch to increase hole-shot and grunt which theoretically will add another 200 rpm per pitch decrease to your current 5200 WOT.

Can you borrow a propeller to test first?
__________________
Is that with or without VAT?
spartacus is offline   Reply With Quote
Old 09 August 2018, 03:07   #4
Member
 
Last Tango's Avatar
 
Country: UK - Scotland
Town: Denny
Boat name: Hebridean Storm
Make: Coastline
Length: 6m +
Engine: Mariner F150
MMSI: 235107505
Join Date: Mar 2013
Posts: 1,153
The 150 Optimax and Mercury's F150 have different gear ratios that equate to about an inch difference in prop pitch.
The Optimax's max revs are listed as 5000 > 5600 rpm
ref RPM/Gear Ratio Reference Chart

I think you can get Laser II with even number pitches. 18" ?
__________________
Last Tango is offline   Reply With Quote
Old 09 August 2018, 03:53   #5
Member
 
Country: UK - England
Town: Chesterfield
Boat name: Sea Quell
Make: Picton Cobra
Length: 5m +
Engine: Mercury 150 4 Stroke
MMSI: 235038298
Join Date: Sep 2003
Posts: 942
Quote:
Originally Posted by Last Tango View Post
The 150 Optimax and Mercury's F150 have different gear ratios that equate to about an inch difference in prop pitch.
The Optimax's max revs are listed as 5000 > 5600 rpm
ref RPM/Gear Ratio Reference Chart

I think you can get Laser II with even number pitches. 18" ?
I think the even pitch laser props are for the small gearcase.. not the V6 optis. Vinny,,, its a shame you aren't nearer.. I have a 17" revolution 4 which I had tweaked to 18" ,,, now surplus. Wouldn't raise revs but would definitely give you more grip and whoosh Are you sure the engine isn't a hole too low... revs seem down for a 19" 3 blade on a 6m.
__________________
Jeff is offline   Reply With Quote
Old 09 August 2018, 04:00   #6
Member
 
Last Tango's Avatar
 
Country: UK - Scotland
Town: Denny
Boat name: Hebridean Storm
Make: Coastline
Length: 6m +
Engine: Mariner F150
MMSI: 235107505
Join Date: Mar 2013
Posts: 1,153
Quote:
Originally Posted by Last Tango View Post
The 150 Optimax and Mercury's F150 have different gear ratios that equate to about an inch difference in prop pitch.
Sorry.. This is wrong, they're both more or less the same.
__________________
Last Tango is offline   Reply With Quote
Old 09 August 2018, 04:44   #7
RIBnet supporter
 
Pikey Dave's Avatar
 
Country: UK - England
Town: South Yorks
Boat name: Black Pig
Make: Ribcraft
Length: 5m +
Engine: DF140a
MMSI: 235111389
Join Date: Feb 2008
Posts: 8,304
RIBase
Quote:
Originally Posted by Jeff View Post
I think the even pitch laser props are for the small gearcase.. not the V6 optis. Vinny,,, its a shame you aren't nearer.. I have a 17" revolution 4 which I had tweaked to 18" ,,, now surplus. Wouldn't raise revs but would definitely give you more grip and whoosh Are you sure the engine isn't a hole too low... revs seem down for a 19" 3 blade on a 6m.


The Rev4 prop is the best prop I've had on a rib, not the fastest or most fuel efficient, but it don't half grip.
__________________
Rule#2: Never argue with an idiot. He'll drag you down to his level & then beat you with experience.
Rule#3: Tha' can't educate pork.
Rule#4: See rule#5
Pikey Dave is offline   Reply With Quote
Old 09 August 2018, 05:59   #8
Member
 
Vinny31's Avatar
 
Country: UK - N Ireland
Town: Armagh
Make: Xs
Length: 6m +
Engine: 150 optimax
Join Date: Aug 2017
Posts: 127
Quote:
Originally Posted by Iron Dials View Post
Are you trimming out to achieve WOT?

If itís any use to you...
We have XS650 and Merc 150 4Stroke with 19in prop.
Trimmed out we get 42 kts at 5300rpm- boat feels a little light when trimmed out and fast though.
Recently changed from aluminum to stainless prop. Top speed pretty much the same but new prop makes boat much livelier above 20kts.
Iíd still like more bite in rough weather so may try 17in 4 blade.


Iím trimming out until she starts to get a bit Ďlivelyí , which I presume is chine walking.
__________________
Vinny31 is offline   Reply With Quote
Old 09 August 2018, 06:05   #9
Member
 
Vinny31's Avatar
 
Country: UK - N Ireland
Town: Armagh
Make: Xs
Length: 6m +
Engine: 150 optimax
Join Date: Aug 2017
Posts: 127
Quote:
Originally Posted by Jeff View Post
I think the even pitch laser props are for the small gearcase.. not the V6 optis. Vinny,,, its a shame you aren't nearer.. I have a 17" revolution 4 which I had tweaked to 18" ,,, now surplus. Wouldn't raise revs but would definitely give you more grip and whoosh Are you sure the engine isn't a hole too low... revs seem down for a 19" 3 blade on a 6m.


Iíll grab a pic of the keel and cavitation plate for opinions, if it was an option Iíd be happy to cover p&p costs for a trial?

First things first though will see about engine height
__________________
Vinny31 is offline   Reply With Quote
Old 09 August 2018, 06:07   #10
Member
 
Vinny31's Avatar
 
Country: UK - N Ireland
Town: Armagh
Make: Xs
Length: 6m +
Engine: 150 optimax
Join Date: Aug 2017
Posts: 127
Quote:
Originally Posted by spartacus View Post
Mercury Vengeance stainless steel propellers seem to to get a good write up, and importantly are available in 17 and 18" pitches. Normally drop down a pitch to increase hole-shot and grunt which theoretically will add another 200 rpm per pitch decrease to your current 5200 WOT.



Can you borrow a propeller to test first?


No sure borrowing will be an option but would be the ideal scenario.
__________________

__________________
Vinny31 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 19:56.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2018, vBulletin Solutions, Inc.