Reply
 
Thread Tools Search this Thread
 
Old 13 April 2009, 16:10   #1
Member
 
Country: UK - Scotland
Town: Moray Firth
Boat name: Lochran
Make: Northcraft
Length: 5m +
Engine: Honda BF90 4/
Join Date: Jul 2006
Posts: 72
"what pitch" ... again!

Folks,

Sorry to re-hash such a well discussed topic but....

Just got the new engine on the boat today. Haven't used it yet because it came with a left hand rather than right hand control box/throttle lever. I'm very much a right-handed guy, so will need to wait for the swap.

So, the prop that was ordered for the engine by the shop was a 13 x 13.75.

It's a 5.5m northcraft, weighs about 750kg, and will be used for a mix of diving and family cruising. THe engine is a Honda BF90 4-stroke.

All the props I've come across before - diving Club's 5m Humber/Yam 60; a mate's Delta 5.5/Yam 100 etc have been 19" or thereabouts. It was a 19" on the old Mariner that's just come off the boat, so 13.75 seems a long ways different.

I figure now's the time to swap it, as it hasn't been used, and wonder what would be the best to start off with. 19" again??

Thanks in advance.

D
__________________

__________________
DonMacN is offline   Reply With Quote
Old 13 April 2009, 17:02   #2
Member
 
Pete7's Avatar
 
Country: UK - England
Town: Gosport
Boat name: April Lass
Make: Moody 31
Length: 9m +
Join Date: Aug 2001
Posts: 4,850
Donald, how does the gearbox ratio compare with the other engines, but yes seems a little low. If you use it will they exchange it if it's wrong? bet there is a bit of shuffling feet when you look them straight in the eye and ask.

Pete
__________________

__________________
.
Ribnet is best viewed on a computer of some sort
Pete7 is offline   Reply With Quote
Old 13 April 2009, 17:21   #3
Member
 
Country: UK - Scotland
Town: Moray Firth
Boat name: Lochran
Make: Northcraft
Length: 5m +
Engine: Honda BF90 4/
Join Date: Jul 2006
Posts: 72
Pete,

Don't know about the gear ratios. I'm reading the engine manual as 'bedtime reading' but can't find any reference to that yet. There's nothing in the specification table.

I think I should probably be able to swap it OK, seeing as I had no input into the choice of pitch and it's a big enough outfit. I'll also ask the mechanic to phone Honda's 'tech support' tomorrow and see what they say. I have discovered that optimum throttle will be at 5,300 to 6,300 revs.
__________________
DonMacN is offline   Reply With Quote
Old 13 April 2009, 17:47   #4
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
Judging from the revs MHB100's Zodiac Pro Open was doing with the same engine, I'd try starting with either a 19"x13.75 or a 17"x13.75.
That's assuming the same gear ratio as the earlier Honda 90s.
__________________
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 13 April 2009, 17:52   #5
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
Don - do the Honda controls not allow you to reconfigure as either LHS or RHS the way that Yam ones do? I thought that was standard on most of the lower end controls...

A quick look on the web suggests your gear ratio is prob 2.33, other brands seem to vary from about this down to 2.0 in the 90HP size. So your prop may be turning up to 15% slower for the same engine revs.
__________________
Poly is offline   Reply With Quote
Old 14 April 2009, 02:51   #6
Member
 
Country: UK - England
Town: Gloucestershire
Boat name: Osprey
Make: Osprey Vipermax
Length: 5m +
Engine: E-tec 300 G2
MMSI: TBC
Join Date: Dec 2006
Posts: 4,013
With a 2.33 gear ratio I would start at 19"
__________________
---------------------------------------------------
Chris Stevens

Born fiddler
Chris is offline   Reply With Quote
Old 14 April 2009, 06:36   #7
Member
 
Country: UK - Wales
Town: West Wales
Make: Vipermax 5.8, SR4.7
Length: 5m +
Engine: 150 Opti, F50EFi
Join Date: Sep 2005
Posts: 6,298
Quote:
Originally Posted by Chris View Post
With a 2.33 gear ratio I would start at 19"
So would I.

My Northcraft 5.5 is just about right with a 17" pitch on a DT100 Soozook, which has a 2.08:1 gear ratio. This would be roughly equivalent to a 19" pitch on the Honda 90. If you're loading her up with divers & kit, then you may need the next finer pitch size, which would probably be 17"
__________________
Downhilldai is offline   Reply With Quote
Old 14 April 2009, 13:11   #8
Member
 
Bigmuz7's Avatar
 
Country: UK - Scotland
Town: Glasgow
Boat name: stramash
Make: Tornado
Length: 5m +
Engine: Etec 90
Join Date: Feb 2006
Posts: 5,068
I think mines a 19x13 on a year old BF 90, which without much load on a 5.7. I'll only get 5700 trimmed to the limit on the flat. If you are loaded you will need to go down, as the other guys have said .. I tried a 21 x 13.25 and had to laugh at the result .. I couldnt get it over half revs These motors seem easily choked down at the bottom end of the rev range possibly because of the ratio and if anything I've come to the conclusion that I'd prefer to be slightly under propped, .. I'm away from the boat atm , and will confirm in a day or so that it is the 19
__________________
Bigmuz7 is offline   Reply With Quote
Old 14 April 2009, 18:30   #9
Member
 
Country: UK - Scotland
Town: Moray Firth
Boat name: Lochran
Make: Northcraft
Length: 5m +
Engine: Honda BF90 4/
Join Date: Jul 2006
Posts: 72
guys, thanks very much for all the reponses. I'm sure it's not the 'black art' it appears, but I've never managed to find the time (and never needed to until now) to research the combinations of gear ratios and prop pitch.

I've asked for a 19" and it seems this won't be a problem as long as the one I currently have isn't used. SHould hopefully be up by the end of the week as I'd like to start getting the engine gently run in. There's a few dive trips starting to appear in the calendar and I'd rather not be restricted to 2000 revs!

As far as the controls are concerned it appears they are swappable in that a LH can be reconfigured to be a RH, but surprisingly (to me at least) the cover plate with the Honda branding etc will then be mounted in against the console, with a less protected face to the elements. I phoned Honda UK myself about it today because I just couldn't believe a company of that size hadn't made a 'proper' RH control. Seems they're considering it, but not really likely any time very soon. I'll just need to get out the sealant gun and ensure the box is as protected as it can be.

thanks again
__________________
DonMacN is offline   Reply With Quote
Old 15 April 2009, 07:43   #10
Member
 
Country: UK - Scotland
Boat name: Wildheart
Make: Humber/Delta Seasafe
Length: 5m +
Engine: Merc 60 Clamshell
MMSI: 235068449
Join Date: Apr 2007
Posts: 4,610
Quote:
Originally Posted by DonMacN View Post
As far as the controls are concerned it appears they are swappable in that a LH can be reconfigured to be a RH, but surprisingly (to me at least) the cover plate with the Honda branding etc will then be mounted in against the console, with a less protected face to the elements. I phoned Honda UK myself about it today because I just couldn't believe a company of that size hadn't made a 'proper' RH control.
Nobody does! (well, if they do I've yet to find them). Had Suzuki, Yam & Merc &a borrowed Tohatsu box - all the same story! The only real issue you'l lhave is showing off whose box you have - the hub of the lever usually covers most of the "ugly" bits!

The only truly "cosmetically reversible" one I've seen was an old teleflex thing from about 1970 ish. Only truly reversible because the lever would bolt on at any increment of 90 degrees, so for a "RH" you just spun the lever round 180 deg & mounted it upside down! (no fast idle levers (or neutral catch!) on that box......... Suffice to say the deadman for that control was console mounted!
__________________

__________________
9D280 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 04:27.


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