1991 Merc 50HP loss of power after 10 minutes on first run of season

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Ramsey1

Cadet
Joined
Sep 11, 2012
Messages
7
Got boat on water for the for the first time this season. Still had last year's non-oxy gas in tank. It ran great for about 10 minutes then became sluggish and had a slight inbalance (like a missing cylinder). Could not get it up on plane and brought her back to the landing. At the dock it would not idle down without dying - had to keep the RPMs up. It had been about 12 months since it was last used. Pulled the 3 plugs and they all had a brownish wet look with some little specs of darker particulate on them. Any ideas of fixes.

Thanks.

-John
 
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Dave1027

Lieutenant Junior Grade
Joined
May 25, 2010
Messages
1,078
Re: 1991 Merc 50HP loss of power after 10 minutes on first run of season

First thing to check is the gas tank vent.
 
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Ramsey1

Cadet
Joined
Sep 11, 2012
Messages
7
Re: 1991 Merc 50HP loss of power after 10 minutes on first run of season

Thanks for the reply. The vent was open the whole time.
 
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oldman570

Lieutenant Commander
Joined
Mar 25, 2011
Messages
1,615
Re: 1991 Merc 50HP loss of power after 10 minutes on first run of season

The first item would be to get new fuel and get rid of the old fuel. Check all the fuel filters and the pickup tube screen in the tank for any water and sluggish mix of the fuel. Then check the compression before doing anymore. JMO
Oldman570
 
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