Mercury 402 72-74

[Milduff]

Hello again, I have a 402, serial # 3726839 40hp 2 cyl had a bad stator replaced with cdi unit # 174-5255. Still having problems: good compression
(130) in each cylinder. have spark with plugs out. cannot get engine to fire. Have fuel cleaned and rebuilt carb , what else can i do? I need help. Thanks

** Is it posiible to have a blockage passed the reeds but before piston chamber?? ** Not allowing fuel into the cylinder????

 

[usskydvr]

Re: Mercury 402 72-74

Have you verified that your timing is correct? Not really possible to have blockage between reeds and intake ports. (unless someone left a rag in)

 

[Milduff]

Re: Mercury 402 72-74

My Flywheel mark with #1 TDC in at the pointer. What else can I do to verify? I'm losing my mind with this thing. Could I have some slug from old fuel blocking??? boat has been sitting since 1981.

 

[usskydvr]

Re: Mercury 402 72-74

So your flywheel is on correctly. What about ignition timing. Look on this forum for a "link and sync" procedure specific to your engine..

 

[Faztbullet]

Re: Mercury 402 72-74

Take a squirt bottle and spray a little fuel into each cylinder and reinstall plugs, if it pops off its a fuel problem if not its a electrical. I have seen 2 types of problems with these engines: (1) trigger magnet on flywheel hub moves downward and causes weak voltage to switchbox scr's (2) Check to see if it will jump a 3/8 gap and must be bright blue with a "pop" to it, if not capacitor in switchbox is leaking,internal rectifier in switchbox is bad or stator voltage is low to switchbox which leads you back to flywheel (possible weak magnets) as all these will not let plugs fire under compression..

 

[Milduff]

Re: Mercury 402 72-74

Fatzbullet, thanks for the reply. tried fuel in chambers.....nothing! bright blue spark at both plugs. If i remove one plug, either top or bottom, the engine will "pop" at end of start cycle (when i let off of the key) man this thing is giving me a headache.....engine has sat in heated garage since 1981.