Spark Plug Compatability

[yachtinglimited]

Hi, I have been working on our outboard spares kit for next season and was wondering how interchangable spark plugs are. The Mariner 40 we have takes QL78YC plugs which we carry lots of spares of. Would those also be correct to use in our Mariner 5 auxiliary (which currently has a NGK B7HS in it)? Thanks, Mike

[9D280]

Mike,

Firstly, welcome to ribnet!

There are plenty of online cross - make equivalent charts. Thatr wil lat least tell you if they are similar.

Spark plugs are rated on a few things, including their ability to conduct heat away. If the two types are similar physically, then in theory the "wrong" one would let your engine run, but may alter the performance once it warms up. (Heat dissapation etc) Some also carry internal suppression, so you also may find your radio starts buzzing at you.

If they don't turn out to be identical, but they are physically similar, then there are two ways of looking at it:
1) Carry 2 sets of spares so the correct plug goes in.
2) live with possibly reduced performance on one of your engines until you can get back ashore for a new one.

[yachtinglimited]

Thanks 9D280. It seems appropriate that I am welcomed by a fellow Scot. I have been lurking for a long time and have found Ribnet very useful so far.

I suspected the answer would be like you say so I have ordered a couple of the correct ones that the engine already uses. One engine is water cooled and the other is air cooled so better to play safe than sorry I think. I had been hoping to keep the spares kit as simple as possible but I suppose now it will be even better because I will have loads of spares and know they are interchangable in an emergency.

Thanks again.

[Locozodiac]

The equivalent to NGK B7HS plug is Champion L82C. B7HS is factorry gapped to 0.7 and same B7HS-10 or BR7HS-10 to 1.0 mm gap.

Happy Boating