Mariner plugs??

[gwhaling]

Second hand question for my dad. He has a 75 hp mariner that fouls the plugs constantly. It's a 75hp 85 model serial 6468589. The manual he has says champion L78V plugs. The champions foul constantly. Any better recomendations. He put in a set of splitfire plugs from a early 70's evenrude and it seems to be better. That's why I am askingabout any plugs that are better than the champions that are for his motor.

 

[jwilkey84]

Re: Mariner plugs??

I have a 40 from the same era, it takes a NGK B7HS 10. I was always fouling plugs too, even with NGK's, but I have been told champions are junk. I have recently done major tuning on my carb and hopefully that will cure the problem. I was putting way too much fuel through the carb, maybe you are doing the same thing. How does the motor run? I thought mine ran ok, but now it runs twice as smooth, and hopefully I won't be fouling any more plugs.

 

[Silvertip]

Re: Mariner plugs??

Don't believe everything you are told. Champions are not junk. If an engine maker specifies Champions, it's for a reason. If the NGK's are specified, run them. If you have a problem with plug fouling it is generally not the fault of the plug unless you have installed the wrong plug (wrong type or heat range).

 

[gwhaling]

Re: Mariner plugs??

Its putting a lot of fuel through. Just from the smell riding behind the boat. I am pretty sure the carbs need work etc... Just looking for a little better plug than the champions to finish are last few days at the lake. Its been starting and running a good bit better with the 10 year old used splitfires for the last couple of days.

 

[jwilkey84]

Re: Mariner plugs??

look at your adjustment screw on the carb. Keep in mind the position of the screw. Start to turn the screw in clockwise, counting the resolutions as you go, until the screw is all the way in. Write down the number of turns you made. On mine the number was 4 and 1/2 turns! It should only be somewhere around 1 and 1/2 turns out. So, now that you have the screw all the way in, start to turn it counterclockwise 1 and 1/2 rotations. This is just rough starting point, you will have to play with this while it is running to find out where the sweet spot is. Generally it won't be more than one turn on either side of 1 and 1/2 turns out. This worked really good for me, it runs better and hopefully I will quit fouling plugs too

 

[Chris1956]

Re: Mariner plugs??

GW - You can use the NGK version of the L-78V, but it will not provide much improvement. I think the carbs likely need work to set the floats correctly, seats don't leak etc. The plugs almost never foul, if the carbs are setup correctly.

As far as I know, regular gap-stype plugs were never specified. I would be careful with the splitfires as well.

 

[Bluedog]

Re: Mariner plugs??

Will runnig the carb too lean overheat the motor?

 

[Chris1956]

Re: Mariner plugs??

Bluedog, Running the carb too lean will cause some additional heat and the lean mixture does not lubricate as well. These two factors together will cause the cylinder to seize, or the piston to develop a hole, or both.