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Replacement Spark Plugs for b77 Merc 150HP

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chris

Regular Contributor
" Folks, I have been using the

" Folks, I have been using the stock spark plug for my inline 6 150HP merc. It is an NGK BUHW gapless spark plug. They seem to foul easily, and was wondering if there is another plug, with a standard gap that I could substitute? "
 
Most of the V-6's use BU8

Most of the V-6's use BU8H. What is your serial #?
You also might check that the motor is running at the proper temperature.
 
You can also use a Champion L

You can also use a Champion L76V Spark Plug. I use these and they seem to last a whole season. Just a personal preference.
Good luck and have fun on the Water.
 
" MD and BC.. Thanks for the

" MD and BC.. Thanks for the feedback. The Champion L-76V is an exact replacement for the NGK BUHW(gapless). I was interested in a plug with a gap. I had heard that the newer Merc. Outboards run gap plugs, and was wondering if any of these were suitable for my inline motor. FYI, my serial number is 4765432 "
 
" Chris,

Do not put gap plu

" Chris,

Do not put gap plugs in your motor. You will damage the engine.

What type of fowling do you have? Aluminum flakes or oil? Set the maximum timing at 21* regardless of the sticker on the front. Use good quality midgrade fuel and quality oil at 50:1. Those plugs should last years. Check the distributor cap for carbon arcing. You wide open throttle rpm should be 5800 rpm or higher. Lower than that and you are over propped and lugging the motor. Those old inlines like to rev up and the 1500 gets is power high in the rpm range.

Hope this helps!

Kirk S. "
 
Thanks for the replies. The

Thanks for the replies. The fouling is oil. I guess I do not understand why this motor with CDI ignition allows the plugs to foul easily. I had an old Johnson with magneto-points-condenser ignition that ran 24::1 mixture and J4C Gap plugs. It never fouled a plug.
 
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