'67 Evinrude 9.5 - wrong Spark Plugs

[crxess]

Bought this a few weeks ago. only had the chance to run it in river WOT once. (after carb rebuild) Ran nicely with smooth top end and good Idle.

Ran into Heavy Grass cover yesterday and finally had t oshut down and drift out. Even with weed guard the prop and lower end got completely tangled. Checked for overheat and everything was ok.

Pulled Plugs today to inspect/replace if needed and ck Compression. compression ok @ 70/70 on rope pull.

Plugs are Champion J8C

Reading here, everyone recommends J6C for most of these motors.
Evinrude Sticker says J4J which would now be J4C

Which for general usage? - Some WOT but mostly blat control around fishing areas.

Why would it have J8C installed? Looks like a Hotter plug. Same electrode length but much thinner porcelain center.

 

[JB]

Re: '67 Evinrude 9.5 - wrong Spark Plugs

J8C is far too hot for that engine.

You can use J6C for trolling and low speed operation or J4C for all-round use.

 

[ezeke]

Re: '67 Evinrude 9.5 - wrong Spark Plugs

The J4C supersedes the J4J and is the recommended plug. The J6C is somewhat hotter and is sometimes used for sustained low-speed running.

Some users have reported that the J6C is better for badly worn 9.5 motors that have low compression.

 

[crxess]

Re: '67 Evinrude 9.5 - wrong Spark Plugs

Thanks!

Think I'll run with the J6C plugs at least until I do the decarb and see if things change.
Those J8C plugs looked like they were running very hot. Not melting or anything but White ash on the grounding wire and porcelain was spotless.

 

[crxess]

Re: '67 Evinrude 9.5 - wrong Spark Plugs

Purchased J6C plugs, gapped at .030 and hit the river.
First time I have been in the boat alone.

Ran scary fast with just me. LOL - Scary fast is slipping/sliding on the water in high winds at 20mph at 2/3 throttle in a 10' Plastic boat.
I'm used to 12mph WOT and hooked up with the wife on board.
Was kind of fun though