Author Topic: New Gas in an Old Motor???  (Read 790 times)

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Offline Cookiemann

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New Gas in an Old Motor???
« on: April 18, 2009, 12:28:21 PM »
I have a '79 Starcraft Aluminum run-about with a 140Merc I/O.  Should I be adding a lead additive to prevent damage to the head from running normal pump gas?

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Offline jgalar

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Re: New Gas in an Old Motor???
« Reply #1 on: April 25, 2009, 04:08:28 PM »
unleaded gas came out in 74 or 75...

Offline Rex in OTZ

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Unleaded gasoiline era
« Reply #2 on: April 29, 2009, 07:24:30 AM »
I do know they came out in the mid -1970's with unleaded, they finally had agriculture go unleaded in the early 1978-1981 time frame lots of folks getting the heads/valves done at machine shops for old tractors.
you shouldent have any problems with new gas might want to use priemimum instead of low octane stuff.
The lower the octane rateing the easyer it is to burn (this stuff is prone to back fireing "pre-ignition"), the higher octane rateings are more resistant to pre-ignition when run in high performance engines large displacement engines since a 140 is a high performance in its day treat it to the good stuff.

Offline Gary G

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Re: New Gas in an Old Motor???
« Reply #3 on: April 30, 2009, 04:05:30 AM »
No lead additive needed. Your outboard motor is 2 cycle and doesn't have valves in the head (it has reed plates). However, avoid the 10% ethanol if possible. It deteriorates rubber hoses, gaskets, etc. Some states require the 10% ethanol gas.

After re-reading, perhaps I am wrong. Is your engine a 4 cycle? I am not familiar with the inboard-outboard engines.
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Offline Rex in OTZ

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Re: New Gas in an Old Motor???
« Reply #4 on: April 30, 2009, 11:22:10 AM »
Yea I forgot about fuel imcompatability, I know that sno-go racers had been blending 100LL aviation gasoline ina 1/3 ratio with unleaded to boost octane
Running straight av-gas in a 2-cycle is bad on them it raises hell with the crankshaft seals made that mistake on a old Yamaha 340 sno-go

My guess you have some sort of monster in-board/outboard 2cycle motor, what it a 4 cylinder?
I have a 2004 Mercury 210 (v-6) inboard jet boat, had lent it out for the summer to some fish reasearch guys, they fuel'd outta 55gal drums, they ended up pumping quite a bit of water in my fuel tanks draining the carbs is really important after finding water contamination the Racor fuel filter I had on it wasent a water block type, problem is now I have 3 dual carburators with aluminum corrosion started in them (shure was a booger getting that mess cleaned up) remember the carbs have different jets for each position so dont do any swapping them round!!