Reply
 
Thread Tools Search this Thread
 
Old 26 June 2006, 18:01   #1
Member
 
Andy JC's Avatar
 
Country: UK - England
Town: Bristol
Make: Honwave T35AE
Length: 3m +
Engine: Tohatsu 18hp
Join Date: Feb 2006
Posts: 374
What could be wrong here then?

Ok, some advice much needed on this one please...

I've just bought a 3.4 meter Zodiac fastroller(acti-v) with a 15hp Johnson both of which are just over a year old. I took it out on Saturday for the first time only to find that I seem to be getting a problem with either Cavitation or Ventilation. While accelerating it's not long before the prop totally looses grip and gives a very similar effect to a car when wheel-spinning. It's quite severe to the point that I have to throttle right back before it gains grip again. My first thought was to play around with the trim position and found that when trimmed fully in it is slightly better but it still happens. I have checked that the shallow water drive is not engaged and the prop is in good condition, just a slight bit of paint wear. Moving people around in the boat also seems to help a little but I am at a loss as to what to try next.
I have read somewhere that ventilation can be caused by exhaust gases flowing incorrectly and wondered whether this could be the problem but thought it unlikely on a reletively new engine.
Has anybody got a similar boat/engine setup and experienced the same kind of problems?

All comments apreciated...

Cheers
Andy
__________________

__________________
Andy JC is offline   Reply With Quote
Old 26 June 2006, 18:07   #2
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
When it gives the impression of cavitating/ventilating, is there any drive forward at all?
What's the bush in the propeller like? Very unlikely to be your problem, unless an older defective prop has been fitted.
__________________

__________________
Downhilldai is offline   Reply With Quote
Old 26 June 2006, 18:23   #3
Member
 
Andy JC's Avatar
 
Country: UK - England
Town: Bristol
Make: Honwave T35AE
Length: 3m +
Engine: Tohatsu 18hp
Join Date: Feb 2006
Posts: 374
Hi Downhilldai

No, there's no drive at all when it starts happening, the boat almost comes to a stand still before it starts gripping again (quite frustrating as I get the impression that otherwise it would really shift!)
Not sure what the bush in the prop is like, can this easily be checked by removing the prop? Are you refering to the spline? (presuming this model of outboard has a spline and not a key setup?!?) Must admit the prop looks almost new so would guess that the bush should be alright but certainly worth checking out I suppose
__________________
Andy JC is offline   Reply With Quote
Old 26 June 2006, 18:42   #4
Member
 
Country: UK - England
Town: Torpoint
Make: Avon Searider
Length: 5m +
Engine: Mariner 75hp
Join Date: Jun 2006
Posts: 31
slipping acceleration

I had the same problem with a Zodiac Grand Raid and a 40hp Johnson.
I had the prop bush replaced which made things slightly better but still didn't really solve the problem so I had the engine checked over - no problem there though.
It was a weird on/off situation where one day it would be ok and the next slip terribly.
I eventually realised that a repair to the floor had altered the shape of the keel and even the slightest reduction in the amount of air in the keel would make the problem worse.
Heading into a strong wind would help lift the keel and the boat would run really well.
The pitch of your prop can also have an effect on cavitation so it may be worth checking suitability to the boat.
__________________
neilhope is offline   Reply With Quote
Old 26 June 2006, 19:01   #5
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
Were the outboard and boat packaged together from new?
Have you spoken to the previous owner to see what they have to say about it, or did you buy from a dealer?
__________________
Downhilldai is offline   Reply With Quote
Old 26 June 2006, 19:22   #6
Member
 
Country: UK - Scotland
Town: Fife
Make: valiant 490R
Length: 4m +
Engine: 75
Join Date: Jan 2006
Posts: 12
make sure the keel of the dinghy is there and that it is inflated fully
__________________
tetris is so unrealistic
yeehaa is offline   Reply With Quote
Old 26 June 2006, 20:56   #7
Member
 
Country: UK - Wales
Town: swansea
Boat name: Too Blue
Make: BLANK
Length: 8m +
Engine: Suzuki DT225
Join Date: Mar 2004
Posts: 12,791
Well if it is trimmed correctly and you have people sitting at the back then it must be the wrong prop or the rubber hub is slipping(if it has one).

I have a Quicksilver 310 with a suzuki 15hp and it does almost 25mph - it's great fun!!! We have had the cavitation you mention but only because the tilt lock things(or reverse lock) weren't released and the engine wasn't down properly.
__________________
codprawn is offline   Reply With Quote
Old 27 June 2006, 03:31   #8
Member
 
Country: UK - England
Town: Oldham
Boat name: Aqua Vitae
Make: Ribcraft 4.8
Length: 4m +
Engine: Yamaha 75hp
MMSI: 235115057
Join Date: Jul 2005
Posts: 331
You could try getting in touch with MGA Watersports in Rochdale, of all unlikely places!

http://www.ribz.co.uk 01706 379669

There's not much on the website but give them a ring. Shaun seems to know his stuff and is a Zodiac dealer - he works their stand at the boat shows.

Good luck,
Tim.
__________________
Northern Tim is offline   Reply With Quote
Old 27 June 2006, 03:54   #9
Member
 
Country: UK - England
Town: Macclesfield
Boat name: Aqua Fresh
Make: Zodiac Medline
Length: 5m +
Engine: 60hp Yamaha
MMSI: 235051988
Join Date: Feb 2006
Posts: 333
Zodiac 340dl

I had same problem with my fast roller (2003) 340 with a yam 15 on,it usualy happens when there is not enough weight in the rear, but some times this is unavoidible in such a small craft, i fitted doel fins to the engine which greatly improved the handling and general overal stability and stopped cavitation , but they did slow it down a bit

before the yam 15 i used a 15 mariner long shaft which was brilliant but kept grounding the skeg and had dificulty putting in the boot of the car

the long shaft performed better than the short although you are only supposed to use a short shaft on that SIB

Andy
__________________
floater is offline   Reply With Quote
Old 27 June 2006, 19:57   #10
Member
 
Andy JC's Avatar
 
Country: UK - England
Town: Bristol
Make: Honwave T35AE
Length: 3m +
Engine: Tohatsu 18hp
Join Date: Feb 2006
Posts: 374
The boat and engine were packaged together from new so pretty sure it's the correct prop.
Thinking back the inflatable keel might have been a little off centre, didn't think that would have a detrimental effect but after reading these posts maybe that could have been to blame.
As for weight distribution, we had 2 blokes near the back and 2 women on the front bench so I think it should have been fairly even.
The rubber hub slipping could be a posibility, definately worth wipping off the prop to have a look me thinks.
The doel fins could be worth considering if I don't manage to sort it, I'd rather not drill the anti-ventilation plate on a nearly new engine though, bit of a last resort really.

Thanks for all the input guys
__________________

__________________
Andy JC 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 23:37.


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