Mercury 7.5 hp short shaft

[secondopsman]

Evening all
My friend has just picked up a cheap 7.5hp Mercury(thunderbolt ignition?)
Been stood for a fair few years.
So we thought we would have a go at a service.
Carb off with a good clean and fresh pertol/oil mix.
Fitted new impellor.
Greaseed up etc.
But then it came to the spark plugs.I have never seen anything like them
They look normal except there is no arm on the bootom of it.
Bit difficult to describre really but on a standard type plug there is the little pin on the bottom with the arm over it that you gap with the feeler gauges.
These dont have that arm.The pin is there and thats it.
They do work as we have now had it running but like to replace.
Have got any pics but engine is the same as this.

[Alzi]

Don't worry lots of 2 stroke plugs are like that (No apparent electrode) I have been told its to help stop them fouling up , But I dont know, Mine in my 75 mariner are the same.

I got my local Motor factors to get mine from NGK and saved quite a bit.

Alan.

[secondopsman]

Thanks for the reply and at least i know there not broke now.
I did ring quite a few motor factors and none of them could cross reference the plugs

[Alzi]

According to ribs marine parts its a B9HS-10 (NGK).

you would have to check your ENGINE NUMBER first .

Not sure if thats any help , Alan

[secondopsman]

Alan
Thats brilliant thankyou
Pete

[Nos4r2]

Leave the surface gap plugs in there. At a guess they're BUHZW or BUHW-2 or something similar. They are rather good.

[secondopsman]

Originally Posted by Nos4r2

Leave the surface gap plugs in there. At a guess they're BUHZW or BUHW-2 or something similar. They are rather good.

There the ones yes.We have no idea how old they are though so thought best to change.Do they not wear out then?
Pete

[Nos4r2]

They do, yes. What do the edges of the central electrode look like?