runs ok with one spark plug unhooked but not visa versa

[Lund_bC]

Nissan 2001 8hp, i notice when i unhook one spark plug the motor keeps running strong, if i do it with the opposite than the motor stalls or struggles a but unless i rev it a bit?
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Thanks!
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[pvanv]

What is your actual model (not year). Have you checked plug condition, swapped plugs?

 

[Sea Rider]

Check that all electrical component & powerhead grounds are immaculate clean and in shinny cond, clean/polish if not. Install 2 new plugs gapped tight to 1.0 mm. If still with electrical related issues, probably one side of ignition coil is shorting or already is kaput.

Happy Boating

 

[TOHATSU GURU]

Dead cylinder. Check your compression and see if it is same on both. Then check for fire on both. If all is well it could be a bad reed on the sick cylinder or a twisted crankshaft...I have never seen a twisted crank on an engine that small, but crap happens.

 

[tommarvin]

Buy a spark checker and check both plug wires, will the spark jump the same on both?

When ignition parts/systems get old/older, weird stuff happens, this is classic ignition/electrical part going out slowly.,something finally.breaks and then you know.

Start with what Sea Ryder and TOHATSU GURU said, then start testing all the ignition/electrical components.

 

[Lund_bC]

hi it's a tohatsu/ nissan NS8B or something like that 2002 or 2003.

It will run with the problem cylinder most time but sometimes it stalls, and revving it up a bit clears it up, sounds better at higher rpm but at idle it wants to die.

Think it can be a fuel or air issue ?

From my check the compression is the same for both and in range.

 

[Lund_bC]

ps, i think there is only one coil on this unit for both, i checked it and took it off, all good, i have switched the plugs and plug wires up also so not there, both spark good

 

[Sea Rider]

Being a 15 year oldie and if used on salt water and not flushed properly could have already a faulty head gasket on that side, not necessarily a cylinder failure. If everything is OK will need to tear head off and check gasket condition. If excessively dried, cracked, deformed change it, torque it to specs, take advantage to check cylinder walls condition. On OB's head gaskets should be changed from time to time to assure perfect cylinder combustion & OB power as a maintenance issue which most are afraid to do so. Although Ignition coil is a one pack coil for both plugs ,you can have one side with issues...

Happy Boating

 

[tommarvin]

Sea Rider, You got me, I'm afraid to change the head gasket. 1988 Force 125,never been changed. I'm proactive and if you say change it I will.

I don't want any problems during prime boating, I feel ok removing snapped bolts I searched it don't have the cobalt bits yet,have torque wrench?

 

[Sea Rider]

Will depend if OB was used in salt or fresh water. Must be missing, acting strange, uneven when all other fuel and electric related parts are working spot on. Head gaskets does corrode internally between mating surfaces, lets small water droplets inside combustion chamber and OB starts to miss, besides nobody re torques head gaskets after break in period or any time after. Old head gaskets tends to become dried, hardened, burnt with use. A new head gasket will seal combustion chambers much better than used ones in time. Check pic, old is a 600 metered hour use faulty gasket, OB dropped dead at full hammer inexplicably. Assumed fuel or electrical related, but no, blown head gasket.



Happy Boating

 

[tommarvin]

Do both spark plug wires go to one coil? There is a power/ignition pack that feeds the coils,one side of these can fail,then the trigger then the stator, if you are sure you have spark to both,

It's a dirty carb clean the idle jet,lots of little holes and main jet take the bowl off to get to jets