Plugs for 90 hp Johnson

[caper_45ca]

I just purchased a 1995 90 hp Johnson .I want to put new plugs in the engine but do not have an owners manual.It has ngk BZ7HS-10 plugs in it now.Does anyone know if this is the correct plug...if not what is? Also this engine is a little underpowered for the boat it is on ...would a set of stabilizer fins help?<br /><br />Thank You

 

[angus63]

Re: Plugs for 90 hp Johnson

NGK plugs are not recommended for OMC/BRP motors.Correct plugs are QL77JC4 Champions gapped at 0.030". Make sure cavitation plate on motor is even or appx 1-2 inches higher than bottom of boat and your trim angle is optimized for cruising. Fins often help reduce rpm to plane but slightly reduce top speed. If you optimize and are still underpowered, sometimes redistributing weight towards the bow will help (fuel, batteries, coolers, in-laws, etc...).<br />Good luck

 

[Silvertip]

Re: Plugs for 90 hp Johnson

Underpowered or overpropped? What RPM is the engine turning at WOT normal load. If its less than 5500 consider a prop with a little less pitch.