Mercruiser 3.0l reluctant to start

A

ACHW

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Sep 20, 2011
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I have a 3.0l mercruiser of 1999 vintage. Suddenly it has developed a problem where it is very reluctant to start from cold. It takes a lot of cranking and use of the throttle to get it to fire, it then runs rough for a 10 seconds or so then settles out, with lots of grey exhaust smoke (doesn't smoke at all once running). Once warm it starts great. It is a little lumpy when idling but nothing drastic. I have checked the choke and is working fine. New primary fuel filter, and spark plugs recently fitted.

The engine also diesels when fully warmed up, not sure it it related but just thought i'd mention just in case.
 
mpdive

mpdive

Chief Petty Officer
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Apr 23, 2011
Messages
567
Re: Mercruiser 3.0l reluctant to start

What is the choke doing when it first starts? Closed, slightly open....etc Your carb could be leaking down. When was the last rebuild? As far as the dieseling goes, either you have carbon hot spots or your idle is slightly high. It should be around 600rpm's.
 
A

ACHW

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Re: Mercruiser 3.0l reluctant to start

The choke is fully closed, the electric part of it seems to work. I have +12v on the purple wire and the choke body heats up. The choke does seem to come off quick. But I have no frame of reference for this so it may be ok. I was thinking that the float was faulty...possible? I have no idea if the carb has been serviced or maintained in the past, but looks as if it has: the screws and bolts look as if they have seen some action. I have had the boat for year and it was perfect till the last time it went in the water.

Yea I thought that the dieseling was carbon...guess i will have to smoke out the neighbours
 
mpdive

mpdive

Chief Petty Officer
Joined
Apr 23, 2011
Messages
567
Re: Mercruiser 3.0l reluctant to start

Run a can of Seafoam through the fuel and then repost. Seafoam works good on carbon and also may just clean the carb a bit. Check your idle too. 3.0 are notorious for dieseling. Make sure you let it idle for a minute or two before shutting it down.
 
A

ACHW

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Messages
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Re: Mercruiser 3.0l reluctant to start

Thanks will give the engine cleaner a go
 
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