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mercruiser fuel issue.......


finnlander

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i have a 19 ft 1973 searay  with a 165 h.p. straight six motor. it says on the side of the valve cover to use leaded fuel. little hard to find in 2013.  have been told todays fuel could damage the valves if run on reg fuel over a period of time. don,t know what the previos owner ran in it but the motor runs smooth and seems to have power. so my question is do i run it on reg fuel or can i get a addative to put in the fuel that has lead or something in it to make up for the unleaded fuel?  thanks alot.

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Most of your auto parts stores carry it auto zone, advance auto.  We used to run it in our old tractors.  It is because the valve seats aren't hardened so the lead acts like a lubricant so when the valves shut they don't wear the valve seats out.

Edited by Chas0218
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Chase hit the nail right on the head, with that year motor you MUST run a lead additive, like he said the lead acts like a cushion between the valve seat and the valve head, and all the other components like the valve springs and the keepers, and the rings in the cylinders, they are made of cast and need the lead for lubrication, I have a 1983 Sea Ray that I rebuilt the entire engine, but used the same valves and heads, they were fueley 202 heads, big intake and exhaust valves and they also ran leaded fuel in this motor, I also used cast rings for a quicker seat time which also require lead for a lubricant, this type fuel makes more low end torque and horsepower, the lead additive I use I buy at Advance Auto, it's cheap compared to using the newer heads just to run unleaded gas, the modern heads just don't make horse power like the old stuff. I also bored the cylinders 30 over so my engine displacement is 355 cubic inches and with the cam I put in it trolls right down to 1.8 mph without using sea bags or a troll plate using 89 octane fuel with the lead additive, works sweet!!

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