Mercury 50 HP Plugs

[zippy83]

Hello....

I am new to the boat world.. Just got my very first boat and I was wondering If the Plugs need to be replaced. I have attached a picture of them. it is for a 1974 Mercury 50HP outboard. It turns on ok.

Any help is greatly appreciated
Thank you
Zippy

 

[Barnacle_Bill]

Re: Mercury 50 HP Plugs

Yes they appear to be carboned up.

 

[zippy83]

Re: Mercury 50 HP Plugs

Yes they appear to be carboned up.

Sorry for the stupid question but does that mean its time to replace them?

 

[oldman570]

Re: Mercury 50 HP Plugs

The plug you are holding looks good to me. A lot of Merc motors call for the use of the NKG surface gap plugs for use in the motors. I run NKG plugs in all my Mercs and they are alot darker than the one your holding. As long as there is no carbon buildup between the center electroid an the outer face they shioud be fine. I carry a spare set of plugs in my boats all the time just increase one dose go bad. Depending on how much the boat gets used should determin when to replace the plugs. If it is only used a day a week or so to go fishing, once a year replacement should be good. If the boat is used more often and is run at WOT and for pulling skiers then you might want to change them out more often. Myself the once a year has worked great, and I do them when I set the boat up for winter storage, That way come time the weather breaks here in the nothern state, I do not have to spend a day to get the unit set to go and Iam out enjoying the water. JMO
Oldman570

 

[zippy83]

Re: Mercury 50 HP Plugs

Thanks for the input. I will go ahead and replace them since its winter and then replace them again in the off season.

 

[CharlieB]

Re: Mercury 50 HP Plugs

Always remember the old adage, 'If it ain't broke...........' That's fine, for a car. You can't walk home from a boat.

I change customers plugs annually, but my customers pay me to ensure that their boat runs reliably all season and when I winterize, I fog VERY heavily.

The fact that your motor accelerates fine tells me that your spark plugs are still firing fine, any carbon accumulation is not enough to 'short' the spark to ground.

A Scotch Bright pad and any decent solvent will easily remove the worst of the accumulation and make the plug look better.

I fully agree with Oldman and highly recommend to all owners to carry a plug wrench and a spare set of plugs "Just in case". I would much rather you have them and not need them, than to need them and not have them.

Run decent fuel, quality oil, a water separating fuel filter, and your plugs can last a surprising amount of time.

 

[zippy83]

Re: Mercury 50 HP Plugs

CharlieB.. thanks for the info...