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MarinerMerc 50hp 3cyl 2 strokenon starter

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paul_liverpool

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"Mariner/Merc 50hp 3cyl 2strok

"Mariner/Merc 50hp 3cyl 2stroke engine No OB343053 has run/started fine since fitted. Kept in garage and home serviced. Failed to start last trip, turns over great- getting fuel-getting a spark on all plugs (hard to tell if spark sufficient due to permagap type plugs). Engine did not attempt to fire at all no coughs/splutters etc. Could anyone offer any suggestions please."
 
"Paul, Is the choke or enrich

"Paul, Is the choke or enrichment device working? Spray some 50::1 fuel mix into the carbs and see if it will fire. If so, either the carbs are clogged or the cold-start enrichment is faulty."
 
"Thanks Chris, yes I have chec

"Thanks Chris, yes I have checked that the solenoid is activating the choke and I have even manually over-riden it at the carb. When cranking the motor with the plugs removed, a mist of fuel mix is expelled from each of the plug holes. Has anyone experienced their ignition timing slipping or changing as a result of the boat bouncing during operation or towing?"
 
"Paul
I use a primitive spark

"Paul
I use a primitive spark tester with just a screw driver stuck into the spark plug cap. Hold the plastic handle (to avoid electric shock) and put the metal of the screw driver approx 10 mm from the engine block. If you don't have electric start, someone else has to pull the cord. You will easily be able to change the gap to estimate the strength of the spark.
Also, check compression.
Robert
Sweden"
 
"Paul, You can put a timing li

"Paul, You can put a timing light onto no. 1 plug wire and see if the timing is close. If so, you need to do a compression check. If compression is good, the problem is likely one of those subtle ones, like the starter doesn't spin the motor fast enough to start, or the choke is inadequate."
 
"Thank you both for those idea

"Thank you both for those ideas, in response to Chris - I have timed car and bike engines while running and static using a strobe but what marks do you align on this model engine? In response to Robert - Does the spark have to be able to jump the 10mm stated and if not what is the acceptable gap? Compression is fine, the engine was running fine prior to this and started at the first touch of the key when I flushed it after last use."
 
"Most healthy ignition systems

"Most healthy ignition systems I have seen jumps 10mm. (It takes approx. 1000 volts/mm). That would indicate at least 10000 volts. In a car system the spark usually jumps the double. From what I've heard, the spark has more difficulties to pass through a gap filled with compressed fuel gases. Thats why regular spark plug gap isn't enough when testing in free air. I can't tell you where the limit is, but I wouldn't rely on a spark shorter than 5 mm.
Robert"
 
"I'll bet the timing has s

"I'll bet the timing has slipped. Did the flywheel key shear? Mine did in a Merc 200 and it drove me nuts! It acted just like yours, by the way.

Jeff"
 
"Thanks Jeff, I'm in work

"Thanks Jeff, I'm in work at present so I can't go look, Would you be able to tell by looking at the shaft/nut at the flywheel? If this was the case wouldn't the flywheel just spin round or could the crankshaft still turn?"
 
"Flywheel has no key, If you d

"Flywheel has no key, If you did't move the timing it should be good."
 
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