Reply
 
Thread Tools Search this Thread
 
Old 25 September 2010, 19:47   #1
Member
 
Country: UK - Scotland
Town: Edinburgh
Boat name: Cobra 76
Make: cobra
Length: 7m +
Engine: Yamaha F250 4.2
Join Date: Aug 2010
Posts: 3
Help please Suzuki outboard problem

Hi

I was out on my cobra rib today and travelling at 38 knots in calm waters. Suddenly the revs rose and the boat almost lost all drive. I stopped the boat and inspected the prop and all looks ok. I set off again but could not exceed 6 knots and all that happens is the engine revs rise but no increase in forward motion. I did not ground the boat or knowingly hit anything to cause this.
If it was a car I would think that the clutch was faulty. Hoping it is nothing to serious!

I would welcome any thoughts please.

Thanks
__________________

__________________
CobraEcosse is offline   Reply With Quote
Old 25 September 2010, 21:41   #2
Member
 
Country: UK - Wales
Town: Llanfair pg
Boat name: just about to change
Make: Aircraft
Length: 8m +
Engine: Outboard
MMSI: 13
Join Date: Jul 2008
Posts: 217
Quote:
Originally Posted by CobraEcosse View Post
Hi

I was out on my cobra rib today and travelling at 38 knots in calm waters. Suddenly the revs rose and the boat almost lost all drive. I stopped the boat and inspected the prop and all looks ok. I set off again but could not exceed 6 knots and all that happens is the engine revs rise but no increase in forward motion. I did not ground the boat or knowingly hit anything to cause this.
If it was a car I would think that the clutch was faulty. Hoping it is nothing to serious!

I would welcome any thoughts please.

Thanks
Although your prop looks good.
It sounds like the bushing in the centre is duff.
This will give you the symptom you describe
__________________

__________________
www.seawake.co.uk
kawasaki is offline   Reply With Quote
Old 25 September 2010, 22:50   #3
Member
 
Country: USA
Town: Oakland CA
Length: 3m +
Join Date: Feb 2005
Posts: 6,653
I agree with Kawa's post.

Could be something like a bad gear in the case, but in that case you probably wouldn't get any thrust at all, hence the prop assessment.

jky
__________________
jyasaki is offline   Reply With Quote
Old 26 September 2010, 04:04   #4
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
If the problem is as the others suggest (and it certainly sounds likely) then the normal way to diagnose it conclusively is: put a line on the prop crossing onto the propshaft (indelible pen / tipex etc); take engine for blast (given how bad you describe you can probably do this without even leaving the harbour) if the mark on the prop and shaft no longer line up then the bush is gone - you need to replace the prop or send the prop away to get repaired (there is a company in Clydebank who have a good reputation for prop repairs - if you search the forum you should find a link)
__________________
Poly is offline   Reply With Quote
Old 26 September 2010, 14:48   #5
Member
 
Country: UK - Scotland
Town: Edinburgh
Boat name: Cobra 76
Make: cobra
Length: 7m +
Engine: Yamaha F250 4.2
Join Date: Aug 2010
Posts: 3
Help

Thanks to you all. You were absolutely right! Will send away to get fixed. Does anyone have an idea what I can expect to pay for a rebush?
__________________
CobraEcosse is offline   Reply With Quote
Old 26 September 2010, 18:48   #6
SPR
Trade member
 
SPR's Avatar
 
Country: UK - Scotland
Town: Central Belt of Scotland
Boat name: Puddleduck III
Make: Bombard
Length: 5m +
Engine: 50 HP
Join Date: Mar 2009
Posts: 2,066
Quote:
Originally Posted by CobraEcosse View Post
Thanks to you all. You were absolutely right! Will send away to get fixed. Does anyone have an idea what I can expect to pay for a rebush?
The last time i needed a prop for my Yamaha I was told, better paying the extra few quid and buy the new one.

This of course only holds up if the prop is not a nice shiny new stainless steel one.

It also gave me the chance to buy a different size / pitch of prop. (opens another can of worms). Which made a big big difference to out of hole performance...

but...http://www.steeldevelopments.co.uk/ is a company that does them, never used them though.

regards

S.
__________________
SPRmarine / SPRtraining
RYA Training Courses & Safety Equipment Sales
SPR is offline   Reply With Quote
Old 27 September 2010, 06:13   #7
Member
 
Country: UK - England
Town: macclessfield
Boat name: Reach Out
Make: Quicksilver
Length: 4m +
Engine: 30hp Tohatsu EFI
Join Date: Aug 2010
Posts: 301
I bet you were happy to find this quick bolt on solution.... I did not know this could happen. Is there any check you can do to predict that this will happen soon. (marker pen / more perminent mark on the prop and centre sounds like a good idea for all props in this case, to see if it has ever slipped).... Do they normally slip a little bit anyway, I guess not ?

Will my 20hp 2 smoke yam have the power needed to get this phenomanon, lol...?
__________________
simsy is offline   Reply With Quote
Old 27 September 2010, 10:07   #8
Member
 
Country: UK - Wales
Town: Llanfair pg
Boat name: just about to change
Make: Aircraft
Length: 8m +
Engine: Outboard
MMSI: 13
Join Date: Jul 2008
Posts: 217
Quote:
Originally Posted by simsy View Post
Do they normally slip a little bit anyway, I guess not ?

Will my 20hp 2 smoke yam have the power needed to get this phenomanon, lol...?
No, they don't normally slip!
The 'bushing' is there to save the drive train
IE , if the prop gets terwatted the bush fails and that saves the rest of the gearbox etc.
Same thing with a shear pin on smaller engines/props.

I would imagine your 20hp will be' bushed' if so, it too will behave just like a bigger un.

Theory is-- it's cheaper , easier an quicker to fettle a prop and its innards than a gearbox etc!
__________________
www.seawake.co.uk
kawasaki is offline   Reply With Quote
Old 27 September 2010, 12:35   #9
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
Quote:
Originally Posted by kawasaki View Post
I would imagine your 20hp will be' bushed' if so, it too will behave just like a bigger un
Yes your 20HP Yam prop has a bush. No way to predict failure (that I am aware of) other than likely to be associated with a prop strike of some sort. Given that its remarkably easy to "ding" a prop a spare prop is a good idea anyway.
__________________
Poly is offline   Reply With Quote
Old 01 October 2010, 16:43   #10
RIBnet supporter
 
gotchiguy's Avatar
 
Country: UK - England
Town: Dinard, Brittany
Boat name: Into the Red
Make: Osprey Vipermax
Length: 7m +
Engine: Evinrude E-tec 250HO
MMSI: 235 076 114
Join Date: Apr 2009
Posts: 1,948
RIBase
As I understand it, on the most modern engines the bush will melt almost instantly if the propeller's motion is prevented, I think then once the prop has cleared the obstacle and given a few minutes, the (now liquid) rubber will re-form around the splines and return to normal operation. Obviously if this happened, limiting your speed/revs until the its replacement would be highly advisible.
__________________
gotchiguy 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 15:00.


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