merc 2007 90 2st starting issue

[ericcs]

i have a problem when starting the engine hot. 2 out of every 3 times, when i hit the key, it backfires instantaneously causing the starter to load up, as the engine kicks back. as soon as i turn the key again, it starts straight away, then idles normally.
yesterday, once, when it backfired, it wouldn't restart. i found that when it kicked back against the starter gear, one tooth on the starter overlapped a tooth on the flywheel and got stuck there, end to end, jamming the starter. i needed multi grips to free it, and noticed it chipped part of the tooth off. it worked fine after.
question is, is the backfiring of the engine caused by incorrect timing, or the mixture too lean or rich?

cheers, eric

[weeman]

Are you using the fuel enrichment button on the key when starting?

Any idea where the mixture screws are? ie one turn out etc

[ericcs]

Are you using the fuel enrichment button on the key when starting?

Any idea where the mixture screws are? ie one turn out etc

only use the enrichment button first up when it's cold, even then it will still backfire
i haven't checked where the mixture screws are set, as i was hoping someone could give me a
base to start at. i'll wind them in tonight to see.
also, is it better to adjust the mixture with the leg underwater(backpreasure) or on the muffs,
it seems to idle better on them?

[weeman]

Have the carbs ever been cleaned?
The base mixture settings depend on the carb prefix numbers, and or jetting, but I have a 2006 model and the base setting is 1 and 1/4 turns out (this is only a base and may change a little when tuning on the water)
Its always best to set the idle with the leg in water then do some good hard runs to see if it bogs, stumbles etc then you can if needed.. adjust mixtures and idle to suit.

Also make sure the throttle plates are balanced correctly so they all open and close the same amount and at the same time.

How the battery? have it checked to make sure its a good one.

[ericcs]

thanks for your help weeman,
all 3 carbs were 1 1/2 turns out, now at 1 1/4, and they were all synched spot on, just adjusted up the rubber wheel so the carbs open up the same time timing advances.
waiting on a new starter gear.
i replaced the battery last year thinking it was the problem
cheers
eric

[Spaniard_King]

Most likely the choke has lost it's prime... common on those 3cyl mercs

[ericcs]

Most likely the choke has lost it's prime... common on those 3cyl mercs

hi garry,
is there a way to test it and what is the fix, as it starts easy when cold, and the back firing happens whether hot or cold without using the primer?
thanks
eric

[Spaniard_King]

Not sure you have a backfire or a lean coff.. if its a true backfire then you must have a faulty reed valve in the inlet manifold.

To Prime the choke... pump the primer bulb whilst engaging the choke using the key.

[ericcs]

Not sure you have a backfire or a lean coff.. if its a true backfire then you must have a faulty reed valve in the inlet manifold.

To Prime the choke... pump the primer bulb whilst engaging the choke using the key.

thanks for the priming tip!
wouldn't a bad reed give it a rough idle?