1975, 115 Johnson Detuned for unleaded gas

[tboltmike]

My engine was detuned in the mid '80's, spark retarted per OMC bulletin, to burn unleaded gas. The dealer said to use premium gas. Not sure wheather twc 2 or 3 was used then.
I understand now that mid grade gas can be used if twc 3 or synthetic oil is used.
Given the advances in fuels and oils since then, may this engine be timed to original factory specs?
Thanks, Mike

 

[F_R]

Re: 1975, 115 Johnson Detuned for unleaded gas

I remember having to de-tune all those motors back then. I wish I still had the service bulletins. They were originally spec'd to run on Premium Leaded gas. The lead part was just to make sure you got the "premium" octane. It was very poor timing on OMC's part, building such an engine in those days. Or maybe just bad luck.

Fast forward to 2008. I haven't kept up with the latest on them, but in my own mind I see no reason why anything would be changed. They would still need the premium gas octane if not de-tuned. If still de-tuned, well......?

The TC-Wxx would have nothing to do with fuel requirements. 50:1 it was and 50:1 it is. It doesn't change the octane.

 

[tboltmike]

Re: 1975, 115 Johnson Detuned for unleaded gas

Thanks, FR. I was hoping to get some performance back.

 

[crb478]

Re: 1975, 115 Johnson Detuned for unleaded gas

So how exactly were these detuned?