Spark plugs for my 1973 65 hp Triumph

[CIMBill]

The manual recommends the gapless plug Champion UL-77V. Which is better; the gapless or the gap?

 

[F_R]

Throw those surface gap plugs into the deepest hole in the sea. Use Champion QL77JC4 plugs gapped 0.035"-0.040".

 

[oldboat1]

I never contradict a man who wrestles alligators, but might add a suggestion. I would get an open air adjustable spark tester and test the ignition system before deciding on plug gap. I believe your motor would produce a 5/16 (?) spark if in good shape, although maybe less. If the ignition is in top shape, a wide gap on the QL77 plugs is the route to go. The weaker the ignition (age affects us all), the narrower the plug gap. A .030 gap might be preferred, for example, if the ignition is showing its age.

 

[racerone]

A good ignition on those jumps a gap of 1/2" with ease !

 

[oldboat1]

^appreciated. I would consider reducing plug gap if ignition output is weaker.