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Aq151b running rough

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wags31

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"i'll try to be as detaile

"i'll try to be as detailed as possible.. i've got a 1987 volvo penta aq151B that i have done everything to and it still backfires when you accelerate quickly. i've set all the timing marks(3),installed a petronix ignition system w/ a flamethrower coil, set the distributor gap at .040 , set the timing at 6 degrees BTDC, new plugs and wires, had carbs rebuilt, yet none of this has fixed the problem.. i've only found one adjustment on the carbs, and i have a workshop book for the motor that says to screw the adjustment screw all the way in then back out 2 full turns.. does this control the fuel volume or air volume, and does screwing it out let more or less in?? is there another adjustment?? i am at a loss, i can't think of anything else to check!! please help, thank you!!!"
 
"Get a Uni-Syn tool (vacuu

"Get a Uni-Syn tool (vacuum air flow meter)and adjust the carbs properly. Seloc explains how, and it has also been discussed in this forum. The 2 full turns is an approximation only. Also, check that the distributor advace weights are free and the springs are not broken. Also, if the distributor does not reach 36º at 4200 RPM, you may want to try advancing slightly the idle ignition timing (but not beyond 10º BTDC)"
 
The correct setting is 8 turns

The correct setting is 8 turns out. Some manuals
have wrong specification.

Regards from Sweden

zz4qk1
 
"thanks for the help guys... b

"thanks for the help guys... by the way, just so you know Lars the manual was pretty close, it was about 2 turns, there are two different carbs - a late model(2 turns) and a newer model(8 turns)... i do have another question though, what is the clear vinyl hose that goes from the fuel pump to the bottom of the back carb??"
 
That hose is there to divert g

That hose is there to divert gasoline to one of the carbs if the diaphraghm in the fuel pump fails.
 
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