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Mercruiser 305 please help

W

waverunning

Member
"i have a 78 with a 305 in it,

"i have a 78 with a 305 in it,ran great for 2 days and now runs good for first ten minutes then boggs and backfires through carb,i have rebuilt carb new fuel pump,water seperator,fuel filter fuel lines and im stumped,idles and runs great till 2000rpm and it all goes to hell,what do you guys think?"
 
"First check the timing if you

"First check the timing if you already havent. then id readjust the carb sounds like a fuel/timing problem. how old are the plugs and wires? sounds like something is breaking down under heat. coil maybe? condenser? choke falling shut after a certain point of throttle . those are a few things that come to mind and i would check
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"plugs and wires new,i will ch

"plugs and wires new,i will check timing,coil is very hot when it acts up,everything is cooler than the coil,could a bad coil cause it to run good one day and bad the next.also my fuel filter is empty when studering occurs and fuel line is pulsating,it fills back up when sitting,boat will idle and putter around lake all day till i hit 2000rpm it starts breaking down"
 
Ryan the coil shouldnt be no h

Ryan the coil shouldnt be no hotter than it's surrounding components. the stuff thats in them breaks down under heat and thats a no good . after the coil cools down then yes it will act normal for a period of time until she just fails all together if you replace the coil Dont use an automotive coil as they wont last very long. gotta go the extra buck and get a marine one. what i would do is get yourself an automotive one just to test it then if thats the prob the get a marine coil . and it does sound like you have a fuel starvation problem . i hate to ask this but is the filter faceing the right flow and no kinks in the lines?
 
Point type ignition??? Use a d

Point type ignition??? Use a dwell meter or feeler gauge to check point gap. Rubbing block can wear and points will rapidly close if distributor cam is rusty or not lubricated.
 
"and it does sound like yo

"and it does sound like you have a fuel starvation problem..." per steve.

Check the anti-siphon valve on the fuel tank outlet; maybe the pickup line is kaput.
 
"hey boys we r all good it was

"hey boys we r all good it was the points they were about .012 reset them at .017 and she runs like a champ!!!!!! thanks guys u pointed me in the right direction,ran good for last hour and it never made it past 10 minutes before ,thanx 2 all"
 
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