1989 70 hp Merc

Bigaceks1

Cadet
Joined
Aug 20, 2011
Messages
14
Idle's up good when not in gear,,but when trying to plane up,it is very doggy,changed out fuel filter and plugs,could it be the stador? Top speed 10 mph?
 

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
17,924
Re: 1989 70 hp Merc

Do a compression/spark test.
Then change/check all hoses and connectors.
Clean the carbs,rebuild the fuel pump.
Ethanol is not a friend to older hoses and inline connectors.
Check for water in the gas.J
 

BatDaddy1887

Chief Petty Officer
Joined
Jan 18, 2009
Messages
463
Re: 1989 70 hp Merc

...I had similar problem and the correct prop helped me. Did you change props?
 

CharlieB

Vice Admiral
Joined
Apr 10, 2007
Messages
5,617
Re: 1989 70 hp Merc

2 stroke idle circuits have to be overly rich, moreso then 'best idle' to provide the additional fuel necessary for the motor to accelerate.

As carbs dirty, the small idle passages show the first symptoms, poor acceleration, as the condition worsens then idle is affected.

Clean carbs, pay very careful attention to idle screw positions, G E N T L Y screw each one in until l i g h t l y seated and RECORD the exact number of turns so that once finished you can reset each idle screw to the SAME position it was before you started. This will save you LOTS of time adjusting idle afterwards.
 

sutor623

Rear Admiral
Joined
May 23, 2011
Messages
4,087
Re: 1989 70 hp Merc

Idle's up good when not in gear,,but when trying to plane up,it is very doggy,changed out fuel filter and plugs,could it be the stador? Top speed 10 mph?

Does this motor have the integral fuel pump in the carb?
 

oldman570

Lieutenant Commander
Joined
Mar 25, 2011
Messages
1,615
Re: 1989 70 hp Merc

You may try checking time sync the carbs along with cleaning with a can of Merc motor tune spray first off. Gas left in the carbs will evaporate and varnish the jets in a short time. Motor tune can be bought at marine dealers for around 10 bucks.
Oldman570
 

BatDaddy1887

Chief Petty Officer
Joined
Jan 18, 2009
Messages
463
Re: 1989 70 hp Merc

Once you get this fixed you may want to check into using Seafoam in the gas tank every now and again to keep it clean as it runs.
 
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