Johnson 90 gas mod?

[Dave Abrahamson]

Hi all and happy New Year<br /><br />There is a sticker on the side of my motor that reads<br /> "This motor has been modified to operate on a minimum 88AKI unleaded gas. Refer to service bulletin; Outboard: #2159<br /> Sterndrive: #3053<br /><br />Has my motor been modified or is this a factory sticker(or both)?<br />The motor in question is a 1983 Johnson V4 90hp Seahorse. I've been running 93 octane for fear that regular unleaded will somehow harm the engine. Anyone else have this placard on their motor?<br />Thanks<br /><br />Dave

 

[Dhadley]

Re: Johnson 90 gas mod?

Actually the 93 may do more harm than good. Stick with the 87 whether the motor has the thick head gaskets or not, no problem. Just make sure its propped out and set up right. Look for 5800 with your average load and stick with Champion plugs.<br /><br />Good luck!

 

[Dave Abrahamson]

Re: Johnson 90 gas mod?

Thank you very much for the quick reply Dhadley!<br />So I take it the mod is just thicker head gaskets? For what purpose? To lower compression?<br />I'll take your advice and run 87 from now on.I don't want to do more harm than good.<br />Thanks again.<br /><br />Dave

 

[Dhadley]

Re: Johnson 90 gas mod?

The main thing is to make sure the motor is capable of 5800 with your average load. And stick with Champion plugs.<br /><br />There could have been some other adjustments made at some time. Someone may have done some jetting and perhaps set the timing back a tad. It may not hurt to check the timing just so you know where youre at.<br /><br />Good luck!