Wont start/strange fault.

[brian crainie]

Hi folks,
this is strange so bear with me.
Engine I got as a spare or repair and had been submerged breifly in water.
Engine is a 4hp 2stroke short shaft mercury with manual start and breakerless ignition.
Turns over on pull fine and free, bore is clean and good compression.
but the spark...
If i take the plug out the cylinder and hold it near the head I get a cracking healthy spark that jumps from the end of the electrode to the block.
If i let the plug touch the block, i get nothing jumping across the plug electrode.
question is why?
is it just he plug is knackered or is there a electrical fault ?
thanks in advance for any help,
Bri.

 

[j_martin]

Re: Wont start/strange fault.

Hi folks,
this is strange so bear with me.
Engine I got as a spare or repair and had been submerged breifly in water.
Engine is a 4hp 2stroke short shaft mercury with manual start and breakerless ignition.
Turns over on pull fine and free, bore is clean and good compression.
but the spark...
If i take the plug out the cylinder and hold it near the head I get a cracking healthy spark that jumps from the end of the electrode to the block.
If i let the plug touch the block, i get nothing jumping across the plug electrode.
question is why?
is it just he plug is knackered or is there a electrical fault ?
thanks in advance for any help,
Bri.

Plug's knackered.

Where are you from?

John

 

[brian crainie]

Re: Wont start/strange fault.

Scotland, outside Glasgow.

 

[brian crainie]

Re: Wont start/strange fault.

Ok folks,
Progress.

Engine will fire up now (good spark)
But will only run on full choke and full throttle at that.
After about 30 seconds (as it warms up?)
it starts to drop in revs untill you put the choke in a notch,
then it stedily drops in revs.
Wont start on any choke position other than full,and once it has ran for a little while(2/3 mins)
wont run on full choke either and only starts for a few seconds on full choke then snuffs it,
wont start or run on any other choke positon or throttle position.
Any help or guidance would be appreciated,
Cheers.

 

[Doernuth]

Re: Wont start/strange fault.

My guess is that the carb is messed up. Rebuild it and set to getting it adjusted right and you should be good if everything else is operating correctly.