1pulled plugs, 1 different appearance to other 3

[Rovernaut]

I replaced my spark plugs on my 86 merc classic 50.<br /> I noticed that plugs from cyl 1,2 and 3 had a little carbon mark on the metal plug rim, yet plug 4 didn't have it, it was clean and only had some fuel residue.<br />I replace the plugs with new ones and today checked them again. same result.<br />I thought maybe plug 4 isn't firing.<br />But I do get spark from it.<br />I have noticed that on the last 2 trips a WOT there is an occassional slip or miss, hard to describe sort of like the prop is slipping mometarily. When I back of the trottle slightly it goes awy.<br />Is it a faulty coil causing an intermittant loss of spark? any suggestions?<br />Could I swap the coils for 1 cyl to another and see if the plug on the change does it?

 

[Clams Canino]

Re: 1pulled plugs, 1 different appearance to other 3

The bottom plug will always look a bit cleaner as everytime the engine stops with the exhaust port open, it gets some steam.<br /><br />Maybe your slip IS a slip?<br /><br />-W

 

[Rovernaut]

Re: 1pulled plugs, 1 different appearance to other 3

Thanks Clams, I swapped my prop with a spare on and see if it makes any difference.<br /> I did try and turn the prop whilst in gear by hand and couls see a slight slip on the bush. It's the bush supposed to slip if it knocks something?

 

[Rovernaut]

Re: 1pulled plugs, 1 different appearance to other 3

Thanks Clams, I swapped my prop with a spare one and see if it makes any difference.<br /> I did try and turn the prop whilst in gear by hand and could see a slight slip on the bush. It's the bush supposed to slip if it knocks something?

 

[Clams Canino]

Re: 1pulled plugs, 1 different appearance to other 3

Yes... but not by hand. Your prop sounds like it is slipping.<br /><br />That said, it's possible to get water into the bottom cylinder via worn out lower end-cap seals, but it's more likely your cleaner plug is just the extra steam.<br /><br />-W

 

[Rovernaut]

Re: 1pulled plugs, 1 different appearance to other 3

Clams, referring to the end cap seals, easy of hard fix, if it was the case.<br /><br />As for plug leads got a set of 4 made by an ignition specialist company.<br />Made me a nice set for $28 AUS total, much better then Mercury dealer @ $34 AUD each! me thinks

 

[Clams Canino]

Re: 1pulled plugs, 1 different appearance to other 3

To do lower endcap seals you gotta pull off the powerhead and then use a puller to pull the bottom endcap. Not easy, and 3/4 of the way to an overhaul.<br /><br />Go with the steam for now. <br /><br />-W

 

[Rovernaut]

Re: 1pulled plugs, 1 different appearance to other 3

This Steam theory conjures up ideas that the only steam can come from the water the motor is sitting in, as you say it's from the exhaust port.<br />Since I mainly do salt water, then the steam must contain salt.<br /> My visions/worries are corrosion??????? caused by the salt.