Fine tuning advice please :)

libellav15

Petty Officer 2nd Class
Joined
Jul 3, 2010
Messages
177
Info - 1972 mercruiser 120hp GM in line 4, pre-alpha leg.

Hi guys

thanks to all excellent advice on here during the last few weeks whilst i have been rebuilding my boats engine.

Nearly there.

Currently the timing is spot on, the idle is smooth, the power is all there.

BUT.. I must have a bit of further tuning up to do to cure one last little problem.

After idling for a couple of minutes, if you try and accelerate and do it progressivly its fine - but try and move the lever forward even slightly too fast and she chokes up and dies.

Any ideas welcomed - could it be idle adjustment on the carb causing a flood when asked for immediate response and not having time to burn off idle fuel overload?

Could it be timing?

Plugs are a lovely tan colour after a run.

Just a niggle i realise and not a problem when pootling about at 4mph on the river - basically at idle - but we are hoping to take the boat ski-ing and need to get out of the hole as fast as possible.

cheers guys

adam

:):)
 

chaparall villain 2

Petty Officer 2nd Class
Joined
Jul 15, 2010
Messages
129
Re: Fine tuning advice please :)

well there are only two thoughts from me ... accelerator pump on carb ... or maybe idle mixture not set right ... other than that if timing is set right at idle i cant think of anything ... sorry
 

searay3

Senior Chief Petty Officer
Joined
Apr 7, 2005
Messages
655
Re: Fine tuning advice please :)

If the carb hasn't been rebuilt, sounds like the it needs it now. I second the accelerator pump. Take off the spark arrestor, look down the throat of the carb. With the engine off, have a partner push the throttle forward. You should see good streams of gas shooting into the carb. If they are not there or trickle, pump is shot.
 

libellav15

Petty Officer 2nd Class
Joined
Jul 3, 2010
Messages
177
Re: Fine tuning advice please :)

cheers guys - sincerely

similar trains of thought as me

nice to know there is nothing obvious i am missing :)

i'll check the 2 idle screws for fine(r) tuning - and check the snakes tongue of fuel is a squirt rather than a trickle

cheers

adam

:)
 
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