Reply
 
Thread Tools Search this Thread
 
Old 08 August 2018, 23:46   #1
Member
 
Vinny31's Avatar
 
Country: UK - N Ireland
Town: Armagh
Make: Xs
Length: 6m +
Engine: 150 optimax
Join Date: Aug 2017
Posts: 145
Time to change prop I reckon

We’ve had our 6m XS since February and on the few occasions I’ve got to use it full throttle I’ve noticed it’s not reaching the recommended rev range.

We’re running an optimax 150 of 2006 vintage and it’s pulling roughly 5200 flat out, seemingly we should be pulling between 5250 and 5750 and ideally I’d like to be towards the higher end of this as we usually run lightly loaded.

It’s currently running the prop seen below, any guidance or recommendations with regards to a replacement? I’m not so bothered about top speed, throttle response and ‘grunt’ would be preferable. Click image for larger version

Name:	IMG_5002.JPG
Views:	235
Size:	268.0 KB
ID:	126307Click image for larger version

Name:	IMG_5003.JPG
Views:	161
Size:	246.4 KB
ID:	126308

Thanks
__________________
Vinny31 is offline   Reply With Quote
Old 09 August 2018, 03:19   #2
Member
 
Country: Other
Town: Dublin
Length: no boat
Join Date: Feb 2016
Posts: 295
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, 07:39   #3
Member
 
spartacus's Avatar
 
Country: UK - Scotland
Town: Aberdeenshire
Boat name: Sula
Make: Ribcraft 4.8m
Length: 4m +
Engine: Tohatsu 70hp + aux
MMSI: 235087213
Join Date: Jun 2007
Posts: 4,521
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, 08:07   #4
Member
 
Last Tango's Avatar
 
Country: UK - Scotland
Town: Denny
Boat name: Highland Bluewater
Length: 6m +
Join Date: Mar 2013
Posts: 1,647
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, 08:53   #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: 1,095
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 [emoji6] 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, 09:00   #6
Member
 
Last Tango's Avatar
 
Country: UK - Scotland
Town: Denny
Boat name: Highland Bluewater
Length: 6m +
Join Date: Mar 2013
Posts: 1,647
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, 09:44   #7
Member
 
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: 11,865
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 [emoji6] 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:Don't feed the troll
Pikey Dave is offline   Reply With Quote
Old 09 August 2018, 10:59   #8
Member
 
Vinny31's Avatar
 
Country: UK - N Ireland
Town: Armagh
Make: Xs
Length: 6m +
Engine: 150 optimax
Join Date: Aug 2017
Posts: 145
Quote:
Originally Posted by Iron Dials View Post
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.


I’m trimming out until she starts to get a bit ‘lively’ , which I presume is chine walking.
__________________
Vinny31 is offline   Reply With Quote
Old 09 August 2018, 11:05   #9
Member
 
Vinny31's Avatar
 
Country: UK - N Ireland
Town: Armagh
Make: Xs
Length: 6m +
Engine: 150 optimax
Join Date: Aug 2017
Posts: 145
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 [emoji6] Are you sure the engine isn't a hole too low... revs seem down for a 19" 3 blade on a 6m.


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

First things first though will see about engine height [emoji106]
__________________
Vinny31 is offline   Reply With Quote
Old 09 August 2018, 11:07   #10
Member
 
Vinny31's Avatar
 
Country: UK - N Ireland
Town: Armagh
Make: Xs
Length: 6m +
Engine: 150 optimax
Join Date: Aug 2017
Posts: 145
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. [emoji106]
__________________
Vinny31 is offline   Reply With Quote
Old 09 August 2018, 11:26   #11
Member
 
Vinny31's Avatar
 
Country: UK - N Ireland
Town: Armagh
Make: Xs
Length: 6m +
Engine: 150 optimax
Join Date: Aug 2017
Posts: 145
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" ?


If I was getting into the 5500-5600 region I’d be happy enough tbh. Seems I have a few things to check first though.
Thanks
__________________
Vinny31 is offline   Reply With Quote
Old 09 August 2018, 11:49   #12
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: 1,095
Quote:
Originally Posted by Vinny31 View Post
If I was getting into the 5500-5600 region I’d be happy enough tbh. Seems I have a few things to check first though.
Thanks
My quite heavy 6m cobra with 150 Opti was right at the upper end on a 19p laser so I'm almost sure you can tweak it by checking the engine height....
__________________
Jeff is offline   Reply With Quote
Old 09 August 2018, 13:30   #13
Member
 
Last Tango's Avatar
 
Country: UK - Scotland
Town: Denny
Boat name: Highland Bluewater
Length: 6m +
Join Date: Mar 2013
Posts: 1,647
I'm running a 19" Tempest on my Merc F150 6.5mtr Coastline and that's revving to 5650rpm at 44kn. (Trimmed right out and getting "twichy") and the hole shot is very impressive.....absolutely no hint of "grip" issues)

Had a Vengence on my previous engine and changed it to a Laser II. The Laser was better.
__________________
Last Tango is offline   Reply With Quote
Old 09 August 2018, 20:28   #14
Member
 
Country: UK - England
Make: Ribcraft
Length: 5m +
Engine: Yamaha
Join Date: Feb 2006
Posts: 309
You can get your current Laser2 worked to reduce the pitch, I had a 20” Laser2 worked down to an 18” for my Humber years ago.
__________________
phantom 19 is offline   Reply With Quote
Old 09 August 2018, 22:23   #15
Member
 
Vinny31's Avatar
 
Country: UK - N Ireland
Town: Armagh
Make: Xs
Length: 6m +
Engine: 150 optimax
Join Date: Aug 2017
Posts: 145
Time to change prop I reckon

Quote:
Originally Posted by phantom 19 View Post
You can get your current Laser2 worked to reduce the pitch, I had a 20” Laser2 worked down to an 18” for my Humber years ago.


That’s food for thought, I’m going to have a look at engine height first and try to determine if it needs raised.
Thanks
__________________
Vinny31 is offline   Reply With Quote
Old 10 August 2018, 16:38   #16
Member
 
Vinny31's Avatar
 
Country: UK - N Ireland
Town: Armagh
Make: Xs
Length: 6m +
Engine: 150 optimax
Join Date: Aug 2017
Posts: 145
Click image for larger version

Name:	IMG_5023.JPG
Views:	138
Size:	232.0 KB
ID:	126318

Apologies for the picture quality, would have needed four hands to hold straight edge and camera etc.

From what I can see the ‘cavitation’ plate directly above the prop is iro half an inch above the bottom of the keel.

From what I’ve read I could probably raise the engine one hole and see how that affects things.
Advice/ opinions appreciated.
__________________
Vinny31 is offline   Reply With Quote
Old 10 August 2018, 18:12   #17
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: 1,095
Yep ,,, one hole up should be fine. [emoji106]
__________________
Jeff is offline   Reply With Quote
Old 10 August 2018, 19:03   #18
Member
 
Vinny31's Avatar
 
Country: UK - N Ireland
Town: Armagh
Make: Xs
Length: 6m +
Engine: 150 optimax
Join Date: Aug 2017
Posts: 145
Quote:
Originally Posted by Jeff View Post
Yep ,,, one hole up should be fine. [emoji106]


Thanks Jeff
__________________
Vinny31 is offline   Reply With Quote
Old 10 August 2018, 19:04   #19
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: 1,095
,,, and then you need a Rev 4 [emoji6][emoji106]
__________________
Jeff is offline   Reply With Quote
Old 10 August 2018, 19:06   #20
Member
 
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: 11,865
RIBase
Quote:
Originally Posted by Jeff View Post
,,, and then you need a Rev 4 [emoji6][emoji106]


Oh yes!
__________________
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:Don't feed the troll
Pikey Dave 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 09:20.


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