Been using the wrong plugs

[Greene]

Motor: 2005 150hp Merc Saltwater Series carb

I've been using BU8H, the plugs there were in the motor when I bought the boat. However, I found out that the plugs should be BPZ8HS-10. The heating range on each plug is the same but the BU8H is a surface plug and the other plug is a gapped plug and has a longer thread length.

Should I expect any changes but swapping plugs?

Andy





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[Kings Marine nz]

You would want to double check before changing - Mercury changed the plug to BPZ8HS-10 when they went away from std two wire coils and fitted the new 4 wire CDM units - along with the new O'ring cyl heads

[Greene]

The plug number is on the flywheel cover and in the NGK plug manual...so it's double checked. Thanks though.

Would using the surface discharge plug cause any performance issues?

[Kings Marine nz]

No difference in performance (H/P ) the service training used to be that a surface gap plug resists fouling when used for extended idling, but from experience I have found that in Merc engines the J gap plug runs better at extended idle also tends to run a lot cleaner on the plug tip. Some people like a surface gap with extended WOT use as there is a belief the piston crown runs a bit colder (never tested this theory myself)
The Z resistor with carb engines isnt needed, but dont try this with a EFI Merc.

[Jay Smith]

The plug that was installed in the motor ( NGK BUHW ) is a surface gapped plug for an anolog ECU or early carb'ed motor.. The NGK BPZ-8H-N-10 is also the upgraded plug for the 280 after Mercury chunked the Champions .. They work GREAT in my customers 280's, they should give you great service..

Jay

[tmouhalis]

How do you know if you have a analog ecu or digital? We can always depend on Jay for spark plug questions and I enjoy and read all your posts. 1997 merc 200 efi stock.

[Greene]

Thanks for all the replies. I'll make the swap and report back after 50 hours or so.