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AQ151C Backfires thru carbs Need help

H

hookdup

New member
"Hello,
New here trying to ge

"Hello,
New here trying to get a friends boat up and running.
it is a 1990 aq151c, engine runs good at idle, has good compression, will run up to 5000 rpm when not in gear, but when under load, during his first ride, it starts to backfire thru the carbs at about 3000rpm, and never make it past there. It will run along at 2000rpm no problem, but that is not enough to break plane.
Where should we start?
Thanks to all"
 
"I think that good place to st

"I think that good place to start would be the timing. Should be 6 degrees before tdc at 850rpm and 32-36 degrees before tdc at 4200 rpm. Then install either a Pertronics or Hot Spark modular ignition with a Pertronics 'Flame Thrower' coil. Lots of threads on this forum on the merit of doing this. Stay away from those carbs until you are certain that the ignition is A1 then, if the problem still exists, more advise will be forthcoming
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"Just seem to love saltwater b

"Just seem to love saltwater boats, being it seems you have to be a magician to get to the rusted back screw on the cap. As we have not got there yet, is this a points system? as such if it is the key was left on for over a weekend, accumulating 50 more hours than the boat had on it.
She had 274 original hours, now like 325, few if any were running. Can the plug wires be changed to standard resistor wires or is it neccesary to have solid core wires?
We added a 10 micron racor, not sure if there is another filter after that,
but again motor will run up and hold at 4-5k not under load with out a hiccup, also starts and idles well, the forward cabr accelerator pump lever was sticking, that was freed up, and if you watch down the venturis both carbs seems to have good downward spray, all the way around the center jet??????/"
 
"It is a point system; get rid

"It is a point system; get rid of them and put in the solid state system = all point (fried) problems solved
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The cap screw was rusted closed on my cap. I had to drain the cooling system, remove the thermostat housing to get at the screw, drill a 1/8" hole in the cente of the screw and use an extractor to get it out. The screw in now covered with plenty of never-seize as now are most of the engine compartment screws I could get my hands on.

The carbs may need attention but forget them until you get the ignition sorted out. Prove one system at a time."
 
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