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Old 08 May 2011, 05:25   #1
Country: UK - England
Town: Dorset & Hants
Boat name: Streaker/Orange
Make: Avon/Ribcraft
Length: 4m +
Engine: 50Yam/25 Mariner
Join Date: Apr 2007
Posts: 5,551
200 Optimax Idle niggle

I recall reading ( but cant find now) a thread about rough idle on one of these . My old one has started doing it now ....

I 'think' one of the knowledgable guys said something about an air valve may be the issue...?

But its almost hunting at anything up to 1500 revs , and after thats its sweet. Not a misfire, just a slight surging feeling for a second then fine for 10 secs (ish) then the same again.

Any ideas - anyone find the thread ?

The new owner has a merc engineer but wondering if I point him in the right direction it may be quicker/cheaper for the owner, gain me points so I can keep using it



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Old 08 May 2011, 06:00   #2
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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: 5,279
Pete why dont you give uncle al a pm I'm sure he would fix you up
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Old 08 May 2011, 07:31   #3
Country: UK - England
Town: bicester
Length: no boat
Engine: outboard only
Join Date: Feb 2009
Posts: 851
it could be the throttle position sensor either sticking or knackered, ot the throttle roller got a wear groove in it, i am now on holiday for a fortnight if this is not the problem give either Robby or Sam a ring at Blackdog marine
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Old 08 May 2011, 08:37   #4
Country: UK - Wales
Town: N Wales Chester
Boat name: Mr Smith
Make: Humber
Length: 6m +
Join Date: Feb 2009
Posts: 4,955
Different block, but our 175 used to hunt at idle, did it fir two seasons, it got worse over time, then started missing sometimes. Then it got v bad, but intermittent. Tried throttle sensor, idle position, injectors!, spark plugs etc etc. Turned out to be a chafed wire on the entry in to to the engine. V annoying! Worth checking the loom where it moves and could rub.

We got a new loom in the end.
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Old 08 May 2011, 08:38   #5
martini's Avatar
Country: UK - Channel Islands
Town: jersey
Boat name: Martini II
Make: Arctic 28/FC470
Length: 8m +
Engine: twin 225Opti/50hp 2t
MMSI: 235067688
Join Date: Jun 2005
Posts: 3,018
Sounds much like one of mine, ever since I changed the loom it hunts a little bit on idle, runs fine otherwise (or it did till I got to Paris )
I've never looked into it in any great detail, it'll be interesting to hear what the verdict is.
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