Evinrude 70 2 Stroke Spark plug boar enlarged

[rosemb]

Hi

I have a Evinrude 70hp 2 Stroke outboard, with the bottom cylinder spark plug boar enlarged. Any recommendations on a spark plug type and gap size. I know that the normal recommended plug type should be QL77JC4, is there a equivalent plug but with a bigger thread diameter?

[ryendube]

Hi

I have a Evinrude 70hp 2 Stroke outboard, with the bottom cylinder spark plug boar enlarged. Any recommendations on a spark plug type and gap size. I know that the normal recommended plug type should be QL77JC4, is there a equivalent plug but with a bigger thread diameter?

should of left this in same thread as origianl anyways.. what did you pull out ?

I guess youd have to match plug length and temp to the original. Are you sure its the size up or was it helicoiled and the coil has managed to come out.

[Vic.S]

The L in the number QL77JC4 indicates that it is a 14mm thread and a 1/2" reach There are 18mm plugs with 1/2" reach but whether thats the size or whether there are equivalents is another matter.

Are you sure your engine has not been "helicoiled" and that the helicoil has not simply come out with the old plug.

[rosemb]

No this engine has not been helicoiled. The cylinder head spark plug aperture has been enlarge, due to I guess by someone stripping the thread. Any idea on the equivalent (QL77JC4) larger diameter size plug

[a70eliminator]

A thread insert is the best way to go, aside from replacing the head. Put a plug in there that has the wrong reach or heat range and you'll need more than just a head.

[jtexas]

A thread insert is the best way to go, aside from replacing the head. Put a plug in there that has the wrong reach or heat range and you'll need more than just a head.

agree

[ryendube]

thats a champion plug 14mm diameter 1/2 " reach with heat range 14

now if you can find a champion 18mm with 1/2" reach and heat range 14 youll be good but you cannot compare that 14 rating to another manufacter as they all vary. and you cannot umm should not use one of a different range, to cold may be acceptable but may will cause poor performance, to hot and you can damage your engine.

do a search, find a champion plug chart. this is not an answer someone will have off the top of there head. Youll have to do some leg work.

[jtexas]

and it needs to be a "Q" type RF interference suppressor plug.

[Vic.S]

and it needs to be a "Q" type RF interference suppressor plug.

Only if a suppressed plug is required. L77JC4 could be used normally if radio interference was not an issue.

What should not be used is a plug with resistive suppression.