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43 Mercruiser wont crank

A

adam griffin

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I've got a 4.3 mercruiser

I've got a 4.3 mercruiser in a 20' monterey which hasn't been cranked since last year. tried to fire it up yesterday but couldn't get the thing to crank. im not getting any spark so i bought a new coil but still nothing. motor was rebuilt two years ago. new distributor last year. any suggestions?
 
"When you say it won't cra

"When you say it won't crank, do you mean it won't turn over, or it will turn over but won't start?"
 
"it will turn but it wont ever

"it will turn but it wont ever start. you can hold it down, give it gas, it just won't start and never sounds like its trying to either. just turns."
 
"My guess is that the lanyard

"My guess is that the lanyard was left in the safety switch and the plastic has relaxed, especially if it cranks and seems to catch but dies when you stop cranking. Try pulling out on the safety switch and crank it to see if it will keep running. If it does, you need a new lanyard or safety switch."
 
"Assuming it has decent compre

"Assuming it has decent compression, the only other thing it needs is gas and air mixture, along with spark at the right time.
You can pull the high voltage wire from the coil to the distributor, and see if you have a nice fat spark to the nearest frame point while cranking. This will tell you about spark.
NOTE: Don't do this if there is spilled gas or gas vapors in the immediate area. Keep an extinguisher handy.
If the spark checks out, then remove the flame arrestor and look for a squirt of gas down the primary carb barrels when an assistant gives her some throttle. (Engine off!) You should also smell gas strongly.
If there is no evidence of fuel, the carb bowl is empty, and you likely have a plugged fuel filter (main or at the carb inlet), or a bad fuel pump.
If it is equipped with an electric fuel pump, this pump will not run except in the "start" position, due to a safety oil pressure switch, that is designed to stop the fuel pump (and hence the engine) in the event of low oil pressure. This seems to make the 4.3 very hard to start after a long layup. Many on this site have had similar troubles, myself included.
You can remove the fuel line at the carb, run some hose to a bucket, and hot wire the fuel pump to see if it works and pumps gas. Again, beware of the extreme fire hazard doing this.
Hope this helps,
Rod"
 
"Adam, If you motor has the s

"Adam, If you motor has the shift assist switch that kills the ignition when you shift into neutral, check to make sure it is set correctly. Sometimes they stick."
 
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