Reply
 
Thread Tools Search this Thread
 
Old 11 September 2009, 05:34   #1
Member
 
Country: UK - Scotland
Town: Ayrshire
Boat name: Raven
Make: Ribcraft
Length: 5m +
Engine: 150 suzuki
MMSI: 235040525
Join Date: Aug 2006
Posts: 653
Prop comparison

Just a note to anybody with my set up; the 3 blade 25"Suzuki (Solas in origin I believe) prop that came with the engine ,performed okay, but I always had the nagging feeling it was the wrong prop, especially after I raised the engine one hole, it cavitated in turns etc, you were constantly looking for grip, I also felt that by the time the engine was approaching max RPM the drag became the dominating factor, because the prop couldn't lift the bow beyond a certain point this limited the speed and at that point the chine walk was considerable. This was pre and post the engine lift.

During the learning process I had a Hydromotive 4 blader 24” sent over from the states, it was a stern lifter (no cup) so the boat plowed , steering it was akin to steering a pig with a rope. It also lost 3 knots 46 to 43. So sent it back, as an expensive waste of time.

I tried 23" Suzuki all the same problems 45 knots, engine bouncing off rev limiter. I also tried various others with varying degrees of success....nagging still there.

So..I bought a Mercury Revolution 4, 23”,engine now over revving 6,100, I've still lost the 3 knots however the acceleration feels 50% better, the bow lift makes a noticeable difference to the mid range speed, the fuel consumption is marginally better, it’s not blowing out anywhere now and it doesn’t walk about any more….. so I now feel this is finally the right prop for the boat.
Couple of negatives, contrary to the accepted theory, at slow speeds (2-4 knots) it produces a small amount more vibration than the 3 blade and the stainless has started to rust already... and won’t let me bling it up much.

Wonder if I could get it re-pitched to 24” without the wife doing something terrible to me.
__________________

__________________
.
IBWET is offline   Reply With Quote
Old 14 September 2009, 04:26   #2
Member
 
Cookee's Avatar
 
Country: UK - England
Town: Salcombe, Devon, UK
Boat name: BananaShark
Make: BananaShark
Length: 10m +
Engine: 2xYanmar 260 diesels
Join Date: Mar 2003
Posts: 4,225
Quote:
Originally Posted by IBWET View Post
Just a note to anybody with my set up; the 3 blade 25"Suzuki (Solas in origin I believe) prop that came with the engine ,performed okay, but I always had the nagging feeling it was the wrong prop, especially after I raised the engine one hole, it cavitated in turns etc, you were constantly looking for grip, I also felt that by the time the engine was approaching max RPM the drag became the dominating factor, because the prop couldn't lift the bow beyond a certain point this limited the speed and at that point the chine walk was considerable. This was pre and post the engine lift.

During the learning process I had a Hydromotive 4 blader 24” sent over from the states, it was a stern lifter (no cup) so the boat plowed , steering it was akin to steering a pig with a rope. It also lost 3 knots 46 to 43. So sent it back, as an expensive waste of time.

I tried 23" Suzuki all the same problems 45 knots, engine bouncing off rev limiter. I also tried various others with varying degrees of success....nagging still there.

So..I bought a Mercury Revolution 4, 23”,engine now over revving 6,100, I've still lost the 3 knots however the acceleration feels 50% better, the bow lift makes a noticeable difference to the mid range speed, the fuel consumption is marginally better, it’s not blowing out anywhere now and it doesn’t walk about any more….. so I now feel this is finally the right prop for the boat.
Couple of negatives, contrary to the accepted theory, at slow speeds (2-4 knots) it produces a small amount more vibration than the 3 blade and the stainless has started to rust already... and won’t let me bling it up much.

Wonder if I could get it re-pitched to 24” without the wife doing something terrible to me.
How close to the limiter were you with the original 25? Diameter, cupping, pitch and rake all have an influence on handling and top speed. Also you have to consider your main use, do you want to ski and wakeboard, go fast or cruise longer distances?
__________________

__________________
Cookee
Originally Posted by Zippy
When a boat looks that good who needs tubes!!!
Cookee is offline   Reply With Quote
Old 14 September 2009, 04:45   #3
Member
 
Country: UK - England
Town: Southampton
Boat name: SMH Rib / War Shot
Make: Ribtec / Scorpion
Length: 4m +
Engine: 10hp Yam / 150hp opt
Join Date: Sep 2003
Posts: 1,894
RIBase
Vibration?

If it's vibrating might be worth getting it checked for balance?

Why all the 4 bladers?
__________________
Searider is offline   Reply With Quote
Old 14 September 2009, 07:38   #4
Member
 
Country: UK - Scotland
Town: Ayrshire
Boat name: Raven
Make: Ribcraft
Length: 5m +
Engine: 150 suzuki
MMSI: 235040525
Join Date: Aug 2006
Posts: 653
Quote:
Originally Posted by Cookee View Post
How close to the limiter were you with the original 25? Diameter, cupping, pitch and rake all have an influence on handling and top speed. Also you have to consider your main use, do you want to ski and wakeboard, go fast or cruise longer distances?
Good question,(because the change in RPM was greater than I expected),the 25" got 5,800,which means the additional drag of the 4th blade on the new prop has had no affect.. the RPM has gone up 300 (possibly more) now on the rev limiter.
My theory was to reduce the pitch by 2" and add a blade to give better grip/surface area to counter the slip.

This prop was also called a medium bow lifting prop by mercury,so I thought the problem encoutered with the Hydromotive wouldn't exist and it dosen't. The Rev 4, apart from it's pitch being being wrong for top speed is as near to perfect as I think I'll get for what I want;pull wakeboarders,good consumption at cruise and better holding,I'd raised the engine 1 bolt hole so that suites this prop.

This engine uses the same leg as the 200/250,which use 16" diameter props.This could be worth having a look at as the boats relatively small and could swing it. I can see no advantage or possibly don't understand, Suzook producing a very low ratio gearbox...2:5-1, apart from marketing hype, It appears (could be wrong here) the only advantage is keeping the blade speed down to a acceptable level of efficency? If they're right it means Merc,Yam evinrude (2:0-1) are all wrong..what do you think?
__________________
.
IBWET is offline   Reply With Quote
Old 14 September 2009, 07:49   #5
Member
 
Country: UK - Scotland
Town: Ayrshire
Boat name: Raven
Make: Ribcraft
Length: 5m +
Engine: 150 suzuki
MMSI: 235040525
Join Date: Aug 2006
Posts: 653
Quote:
Originally Posted by Searider View Post
If it's vibrating might be worth getting it checked for balance?

Why all the 4 bladers?
I think the balance might just be down to me,the vibration has progressively gone away I've put it down to me not seating it right as it is not present at anything over tick over and is a fair bit smoother than the original 3 blader.


I tried a number of 3 bladers as well and came to the conclusion that If your engine combo has a good torque to weight,and can spin it,in my experience there no comparison, (others will no doubt differ),the 4 blade prop just grips the water better...the relatively slow rotational speed, because my gearbox is very low,made me think the only negative with 4 blades; more drag, would not be a concern and this proved to be the case.
__________________
.
IBWET is offline   Reply With Quote
Old 14 September 2009, 08:42   #6
RIBnet supporter
 
jambo's Avatar
 
Country: UK - Scotland
Town: Girvan & Tayvallich
Boat name: Breawatch
Make: Ribcraft
Length: 5m +
Engine: Mercury 150 F/stroke
MMSI: ex directory!!
Join Date: Sep 2008
Posts: 5,787
RIBase
Ian did you try a 5 blader? When I got my boat the guy before me was a skier and he had a High Five on it great for getting up out the hole but I felt it was heavy on the juice and did not get near the high end of the revs. talked to my Mariner dealer and when back to standard 3 blader, which is middle of the road but better fuel figs for cruising and still can get folk up sking.
Cheers Ian hope it works for you
Billy
__________________
jambo
'Carpe Diem'
Member of the ebay Blue RIB cover club
Member of SABS ( Scottish West Division)
jambo is offline   Reply With Quote
Old 14 September 2009, 13:13   #7
Member
 
Country: UK - Scotland
Town: Ayrshire
Boat name: Raven
Make: Ribcraft
Length: 5m +
Engine: 150 suzuki
MMSI: 235040525
Join Date: Aug 2006
Posts: 653
Quote:
Originally Posted by jambo View Post
Ian did you try a 5 blader? When I got my boat the guy before me was a skier and he had a High Five on it great for getting up out the hole but I felt it was heavy on the juice and did not get near the high end of the revs. talked to my Mariner dealer and when back to standard 3 blader, which is middle of the road but better fuel figs for cruising and still can get folk up sking.
Cheers Ian hope it works for you
Billy
Hi Billy

I looked at the high 5,but discounted it as a dedicated skiing prop,have you kept yours? i'd be interested to know what pitch it is ? We've decided on a seperate note to head to St Kilda on the 26th if you fancy a run, couple of Jet ski's with a 8 mtr rib to carry the fuel and a few ribs. it's a long way but should be fun ,launching at Easdale if you fancy it.
__________________
.
IBWET is offline   Reply With Quote
Old 14 September 2009, 13:23   #8
RIBnet supporter
 
jambo's Avatar
 
Country: UK - Scotland
Town: Girvan & Tayvallich
Boat name: Breawatch
Make: Ribcraft
Length: 5m +
Engine: Mercury 150 F/stroke
MMSI: ex directory!!
Join Date: Sep 2008
Posts: 5,787
RIBase
Quote:
Originally Posted by IBWET View Post
Hi Billy

I looked at the high 5,but discounted it as a dedicated skiing prop,have you kept yours? i'd be interested to know what pitch it is ? We've decided on a seperate note to head to St Kilda on the 26th if you fancy a run, couple of Jet ski's with a 8 mtr rib to carry the fuel and a few ribs. it's a long way but should be fun ,launching at Easdale if you fancy it.
Ian
yes i did I am sure it is a 19, I kept just in case but really I would never put it back on. St kilda what a run!! it would be great but it is my wife's birthday and I am in need of brownie points. Have a great run and be safe. Take plenty photies.
Billy
__________________
jambo
'Carpe Diem'
Member of the ebay Blue RIB cover club
Member of SABS ( Scottish West Division)
jambo 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 05:22.


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