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Old 20 September 2011, 08:57   #1
Country: UK - England
Town: NW Surrey
Boat name: Lady Helen
Make: Avon
Length: 3m +
Engine: Out Petrol 3.5 & 15
Join Date: Aug 2011
Posts: 222
Difficult Starting - Mercury 3.5 1983 2 stroke

Real problem getting this to start from cold.

I think it is a choke problem, as covering the air inlet on the carb got the engine firing but soon died ran a bit longer by letting some air in but found it very hard to get the balance right. Needed the choke lever in to get any firing.

Eventually heated plug on gas stove and then it would run.

Once the engine had ran for a few minutes started easily and ran slowly but not quite idle.

The fuel is old (at least the month I've had it but may be a lot older).

Most grateful for any suggestions.

EnglishLes is offline   Reply With Quote
Old 20 September 2011, 09:26   #2
Country: UK - Scotland
Boat name: Wildheart
Make: Humber/Delta Seasafe
Length: 5m +
Engine: Merc 60 Clamshell
MMSI: 235068449
Join Date: Apr 2007
Posts: 4,538
Plug probably a good place to start based on what you said there. Also check your choke. Take the lid off the air box (if it has one) & check the lever is actually moving the chokle plate. If no visible choke plate you probabyl have one of the older carbs where the choke was an enrichening valve (i.e threw more fuel in). Post back if that's what you find, but try a new plug first. Nothing will happen if there's no spark!

1 month old fuel might cause something new & highly tuned to go in the huff, but to put it in perspective when I ran my Merc in after the rebuild, I used fuel that had been lying around for nearly 2 years, then added more oil to make it 25:1 & it started first go!

For the cost of a spark plug, give it a try. If you have a spark friend, ask him / her to megger both it & the new one (insulation test) - it's a good demo of how the insulation eventually breaks down.

9D280 is offline   Reply With Quote
Old 01 October 2011, 14:38   #3
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Country: UK - Scotland
Boat name: imposter
Make: FunYak
Length: 3m +
Engine: 2 stroke YAM 20 HP
MMSI: 235089819
Join Date: Sep 2005
Posts: 9,416
9d280 - I think he's saying "the fuel came with it" in which case I'd assume it could be very old and get fresh fuel in there - if only to eliminate that.

Les, Was the carb drained when you got it? If not you it might be gunked up which would explain the idle problem.
Poly is offline   Reply With Quote
Old 02 October 2011, 05:32   #4
Country: UK - England
Town: salsbury
Length: 3m +
Join Date: Oct 2011
Posts: 1
Hi. Just got an old Mercury 3.5hp. Any Idea where I would get info/parts list/spares? as I seem to have a dodgy coil or something as no spark. John
john goatcher is offline   Reply With Quote

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