Spark Plug Type Recommendation

[Splash]

My manual (Johnson 1989 HP) states I can choose between a "low speed sustained" type plug or a "high speed sustained" type plug.

Which one should I chooose?

My max speed would be around 55 - 60km / hr for around 20 mins max.

Splash

[FNQCairns]

Low speed would probably be a hotter plug, whatever you do make sure it's champion, that engine was built around the plug.

Plugs between brands cross reference like propellers...poorly.

cheers fnq

[Spaniard_King]

Here ya go.. Handy for some of us;)

[Splash]

thanks boys.

which one should i go for (low speed or high speed)?

pros / cons for each?

sk - great chart!

Splash

[Splash]

thanks boys.

which one should i go for (low speed or high speed)?

pros / cons for each?

sk - great chart!

btw - as plugs are always wet, how do know when plugs need to replaced?

Splash

[FNQCairns]

High speed is probably the standard plug, standard plug is fine, if you notice a problem go the hotter one. Your engine is not new, it's an individual now so there is no strictly right or wrong until you notice a symptom, if you know what I mean.

If your plug oils up or the engine is real rough at trolling speed then the hotter may suit you better - it's a crap shoot, most notice a +ve difference from only replacing oldish plugs so it's hard to compare a new type/style/brand of plug against the old.

cheers fnq

[Splash]

thanks fnq - the plugs do oil up consistently - so, i'll go for the hotter ones.

Splash