Reply
 
Thread Tools Search this Thread
 
Old 21 June 2016, 02:41   #31
Member
 
Country: UK - England
Town: East Anglia
Boat name: Nimrod II
Make: Aerotec 380
Length: 3m +
Engine: Suzuki DF20 EFI
Join Date: Nov 2007
Posts: 3,276
Yes I think a lower pitch shold help your situation... but of course it's only in trying another prop that you'll know for sure.

The theory of a 4-blade is that it should help in the midrange where you need the grip to not fall off the plane so much and get back on quickly when you do.

The other accepted theory of a 4-blade is that you usually drop a pitch down from the 3-blade that would be correct for you.

So if a 9" 3-blade would have been a sensible option then in theory a 4-blade should be an 8".

Be interested to hear from others about this as I know the theory but have never used 4-blade props.
__________________

__________________
Fenlander is offline   Reply With Quote
Old 21 June 2016, 03:37   #32
Member
 
Country: UK - England
Town: Retford
Boat name: Spy-sea-one
Make: Mercury
Length: 3m +
Engine: Suzuki Outboard/25/4
MMSI: 235074042
Join Date: Oct 2011
Posts: 3,573
what hes saying is coming down to 9 inch pitch is like coming down a gear with your current prop the engine cant cope with hitting a wave and staying on the plane plus it will get on the plane quicker you will loose a bit of top end speed but that will be a small price to pay with the the performance you will get and a more consistent speed conditions allowing!
__________________

__________________
jeffstevens763@g is offline   Reply With Quote
Old 21 June 2016, 12:46   #33
Member
 
beerbelly's Avatar
 
Country: UK - England
Town: teesside
Make: valiant v570
Length: 5m +
Engine: mercury 100
MMSI: 232012453
Join Date: Apr 2014
Posts: 858
he might not lose any top speed if the higher pitch prop is not allowing full revs at wot. I had a fletcher arrowflash 15 with a mercury 75 the po had fitted a 21 pitch stainless prop believing it would give him more speed but it would barely pull my mrs out on two ski,s and flat out it was just touching 45 but then started porpoising badly so you had to have it trimmed all the way in and couldn't hold top speed .I changed to a 17 pitch and it pulled me mrs out on one ski easily and if I trimmed the motor out a bit top end rose to 48
__________________
beerbelly is offline   Reply With Quote
Old 21 June 2016, 15:14   #34
Member
 
Country: UK - England
Town: Retford
Boat name: Spy-sea-one
Make: Mercury
Length: 3m +
Engine: Suzuki Outboard/25/4
MMSI: 235074042
Join Date: Oct 2011
Posts: 3,573
Beerbelly is right if not achieving WOT you might not loose top speed but I guess in the conditions you had WOT wasn't achievable anyway for any length of time
Reading your original post if the waves were significant enough you would do well to stay in a straight line at WOT and bouncing off waves would be scary.
When you say WOT what was you RPM
__________________
jeffstevens763@g is offline   Reply With Quote
Old 21 June 2016, 17:49   #35
Member
 
Country: USA
Town: Southern California
Length: 3m +
Join Date: May 2016
Posts: 65
Woa guys, appreciate all of the good feedback.






So would you suggest a 3 blade 9 pitch, or a 4 blade 9 pitch?




I honestly don't know what RPM I was running at. That's probably worth buying a small tach to see to ensure I don't over rev. Would you suggest I make the call on the pitch and prop once I know what RPM I'm running at? Thanks again.
__________________
Jlomb436 is offline   Reply With Quote
Old 21 June 2016, 18:14   #36
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
It's almost impossible to optimise the prop selection properly without knowing what the rpm is.
__________________
Poly is offline   Reply With Quote
Old 21 June 2016, 18:22   #37
Member
 
Country: UK - England
Town: East Anglia
Boat name: Nimrod II
Make: Aerotec 380
Length: 3m +
Engine: Suzuki DF20 EFI
Join Date: Nov 2007
Posts: 3,276
>>> a 3 blade 9 pitch, or a 4 blade 9 pitch?

Diffficult call... we can all guess which we might choose but only trying on your boat with your motor and your load will prove which will do the job.

In many ways the 9" 3 blade is the safest option as that's what would have been on that motor as standard in the UK and will give good all round performance on many planing boats.

As I said before in theory to get to the same place with a 4 blade you need to pitch down to an 8".

I see props are cheaper in the USA than here. This looks the sort of thing you need... Solas Prop 1111-093-09 Mercury (48-82815) 9.25'' 9'' Pitch 3 Blade RT 9-15hp | eBay

Obviously check it is the right fit for your motor before ordering.

Edit: Poly is right of course tach readings would be very useful but I'm pretty sure a 9" pitch 3 blade would be a far better starting point than where you are now.
__________________
Fenlander is offline   Reply With Quote
Old 22 June 2016, 03:00   #38
Member
 
Country: UK - England
Town: Retford
Boat name: Spy-sea-one
Make: Mercury
Length: 3m +
Engine: Suzuki Outboard/25/4
MMSI: 235074042
Join Date: Oct 2011
Posts: 3,573
fenlander & poly are absolutely right but i would have a run out in calm conditions with the weight you are going to carry first with a tacho that will be your bench mark, me personally do quite a bit of trialing before buying my second prop.just bear in mind if the conditions are rough you will be off the plane more than on and for safety and comfort it sometimes better at displacement speed anyway.

cheers
__________________
jeffstevens763@g is offline   Reply With Quote
Old 23 June 2016, 16:23   #39
Member
 
Landlockedpirate's Avatar
 
Country: UK - England
Town: St Helens
Boat name: Wine Down
Make: Maxum
Length: 8m +
Engine: Inboard
Join Date: Apr 2012
Posts: 934
Ive played around with all sorts of props, stainless and ali, 3,4 and 5 blade. In the end they all end up on ebay (even the 500 High Five )

My advice is stick with the original diameter and number of blades, unless you have a very specialized set up (you havent) . Play around with the pitch, as said above, dropping down an inch or so will give you better control over the initial stages of planing at the cost of top speed.
__________________

__________________
Landlockedpirate 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 05:43.


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