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Old 26 July 2011, 16:40   #11
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Country: UK - England
Town: Buckingham
Make: Ribcraft 4.8
Length: 4m +
Engine: Mariner 75
Join Date: Feb 2007
Posts: 352
First update:
I checked all of the carb idle settings this evening - the top two were spot on 1.5 turns to lightly close but the bottom one was way out (nearly 3 turns to close).

I adjusted that back to 1.5 turns; throttle advance lever to fully up; pressed choke in whilst turning the ignition key and it started second time (a first for this outboard).

I ran (with a hose) for about 5 minutes to warm up and then stopped for a couple of minutes. Starting warm without any choke but throttle advance on, worked every time I tried.

So it looks like a combination of user stupidity (used to Yamaha starting not Mariner) and an idle screw was all it needed - so many thanks for all of the suggestions.

I'm going to get a spark meter and new plugs just in case however - another good suggestion !
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Old 30 July 2011, 16:10   #12
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Country: UK - England
Town: Buckingham
Make: Ribcraft 4.8
Length: 4m +
Engine: Mariner 75
Join Date: Feb 2007
Posts: 352
Second update:
New plugs today and then a blast across to the Folly Inn for lunch - all sorted !
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Old 17 August 2011, 06:56   #13
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Country: UK - England
Town: Surrey
Boat name: Craghopper
Make: Northcraft
Length: 5m +
Engine: 70
Join Date: Apr 2009
Posts: 15
Carb balance

I've had various starting/idling problems on a Johnson 70 (1994/5) that came with a RIB I purchased a couple of years ago. Gradually clearing out various gremlins and improving operation. Much had been neglected and mal-adjusted. Slow running was a somewhat fast and often hiccupped/died when throttling up away from idle.

Similar to you, the carb idle settings = the top two were spot on - 1.5 turns to lightly close but the bottom one was way IN (just 1/2 turn to close)." Still idling fast but ran sweet once on the go. Checked timing, idle mixture, idle adjustment, etc., etc. No luck.

Then I loosened each of the clamp bolts to the small arm which joins the three throttles together. Caramba!! Idle speed dropped to a sensible and correct speed. One of the carbs had been ever so slightly open and that was what had raised the idle speed.

Hope this helps

Arthur
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