Looking for a spark plug expert today

[BobnLesley]

Having recently bought a 3.5hp Nissan outboard to supplement our existing 3.3hp Mercury unit (both the old/basic Tohatsu 2-stroke unit) I was surprised to discover that they have different spark plugs, the old Mercury has always used NGK BP6HS plugs, whilst the Nissan's fitted with an NGK BP6RHS plug. So what does the 'R' signify and is it important enough to cause a problem if I were to run it on the HS plugs that I already have loads of?

Also disappointed to discover that the new Nissan needs a 50:1, rather than 100:1 2-stroke mix, though both seem happy enough at around 55-60:1.

 

[Plevier]

A resistor to reduce interference that's all. Should make no difference to running.

 

[VicS]

Having recently bought a 3.5hp Nissan outboard to supplement our existing 3.3hp Mercury unit (both the old/basic Tohatsu 2-stroke unit) I was surprised to discover that they have different spark plugs, the old Mercury has always used NGK BP6HS plugs, whilst the Nissan's fitted with an NGK BP6RHS plug. So what does the 'R' signify and is it important enough to cause a problem if I were to run it on the HS plugs that I already have loads of?

Also disappointed to discover that the new Nissan needs a 50:1, rather than 100:1 2-stroke mix, though both seem happy enough at around 55-60:1.

As Plevier says R denotes resistive interference suppression. If you have trouble with radio interference use the "R" type.

Dont forget to set the plug gap to the value stated in the manuals.

Personally I would run both on 50:1 fuel mix

B= 14mm thread size, P = projected insulator type, 6 = heat range, R =Resistor type, H = 12.7 mm ( 1/2" ) thread reach, S = standard centre electrode.

 

[Mistroma]

As Plevier says R denotes resistive interference suppression. If you have trouble with radio interference use the "R" type.

Dont forget to set the plug gap to the value stated in the manuals.

Personally I would run both on 50:1 fuel mix

B= 14mm thread size, P = projected insulator type, 6 = heat range, R =Resistor type, H = 12.7 mm ( 1/2" ) thread reach, S = standard centre electrode.

+1
Dealer explained the expensive and complex research needed for our Mariner 3.3hp when new version had to go to 100:1 mix. Apparently it simply involved changing the sticker and just accepting higher wear rate. No changes to engine.

He said to ignore the sticker and use 50:1 as per older version.

 

[prv]

Personally I would run both on 50:1 fuel mix

+1

It's what I do on my nice little 2006 Suzuki. As I understand it, these engines were designed for 50:1 but later had the instructions (only) changed to 100:1 for emissions purposes. There is often a note that for commercial use (where long life is more important) they should use 50:1...

Pete

 

[BobnLesley]

As Plevier says R denotes resistive interference suppression. If you have trouble with radio interference use the "R" type.

Thanks for that everyone, just what I'd expected/hoped to hear; even if I fired up a radio in the dink, you'd never hear it anyway!

Regarding the oil mixtures, it's actually the new Nissan that specifies a 50:1 mix, the old Merc's run faultlessly for 16 years at 100:1 (actually, probably more like 80 or 90:1) though its perhaps had an easy life - a lot of hours by now, but rarely do we bother to push it hard.

Thanks again everyone.