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Lead Substitute

tboltmike

tboltmike

Regular Contributor
"My 1975 engine was designed a

"My 1975 engine was designed and built in the leaded gas era. When leaded was phased out, the OMC dealer, per OMC bulletin, detuned the engine to run on unleaded and advised to use premium.

I have seen lead substitue additives in the auto stores.
Is anyone familiar with this stuff?
Would it allow me to run on regular gas?
Would it allow the engine to be up-tuned to orginal specs so I can get the performance back?
Thanks, Mike"
 
"in the mid 80's there it

"in the mid 80's there it was thought to be a huge prob,when it has turned out not to be......i rem buying some stuff called TK-7.lead additive...
the procedure you are referrng to,was to install thicker hd-gaskets,and reduce timing......
I did this ,on my 1984 185...and it was a dog...so i went back and re-set it up original and used tk 7..
Now,....most dont worry about it.....there def ARE lead additives.....but,i think u would just be adding to the expense of your already high gas bill...ESPecially,on a 75 engine..."
 
"I assume your engine is a 2 s

"I assume your engine is a 2 stroke.

High octane fuel is not generally necessary in a 2 stroke.

The lead substitutes you see are, I think you will find, intended for four stroke engines that required the lead as a valve lubricant. 2 strokes do not have valves like 4 strokes therefore there is no point in adding a lead substitute. 4 strokes with hardened valve seats do not require it either."
 
"JWB and Vics...Thanks for the

"JWB and Vics...Thanks for the replys!!

The de-tune done to mine was retarding the spark. The heads were not touched. I lost about 3 mph and I'm sure some efficiency. I didn't know if the additive was for octane ,as you say, for the valves.
The manual says use "Premium or regular leaded gasoline with ...an pump posted 89 octane rating".
So which octane fuel (we have 10% ethanol here) should I use and can I safely time the spark to the orginal setting?
Thanks, Mike"
 
"I'd experiment I think bo

"I'd experiment I think both with fuel grade and ignition timing. If you can get it to run at the original timing or somewhere in between my guess is that would give best results. I would definitely try to avoid additives. Pity about the ethanol, it absorbs moisure I believe and affects old fuel hoses etc. It also may need carb jet changes to enrich the mixture."
 
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