Unleaded Gas & Valve Seats

[JimK]

Does anyone know if older gasoline marine engines are vulnerable to valve seat damage from running the engines without the lead additive? My understanding is that car manufacturers began using hardened valve seats to avoid premature wear on the valve seats when unleaded gas was mandated . Is there a generally understood year when marine engines may have gotten harder valve seats or did they possibly always harder valve seats due to the more demanding marine requirements?

[prowlersfish]

Don't even worry about it . Burnt valves are rare on marine engines , stuck or rusty valves are more common due to lack of use or water intrusion . Marine engine used in pleasure boats rarely get the hours to wear out anything , lack of use and maintenance is the cause of most issues .

But here are my thoughts on lead in gas vs valves . Back when I first started working on engines , burnt valves were common , leaded fuel was used. Unleaded be came available everywhere in 74 as the 75 cars had to use it by law . I also believe leaded fuel lead levels where lowered around then . So hardened seats came around about then and would cross over to marine based on automotive blocks ,maybe a slight delay do to old stock .

Here's the catch , long before unleaded became law American/Amoco premium had no lead . I don't what year they started but I remember that's all my Dad use in the 60 for our outboard . In the 70s I started work at a American station . We did our share of valve jobs . But never on the Cars that ran the unleaded premium . while lead lubed valves it also left deposits that caused valve issues .


So bottom line nothing to worry about , and if you still do they make additives ( lead substitute ) . IMO a waste of $$ unless it makes you feel better .

[JimK]

Thank you very much for the great information. With as many older marine engines that are still being used and run on unleaded gas, I assumed it that it was probably not an issue but did not know why. It is especially interesting knowing that American went to unleaded in their premium fuel long before it was required for emission purposes.

Thanks again, I really appreciate all the information.

[The Dog House]

Like most things the government does, removing the lead from gasoline had several false starts. The engine manufacturers started hardening the valve seats in 1972 for the 1973 models before the mandate was postponed. I know this because my brother purchased a 1973 Dodge Charger with a Chrysler 318 and was worried about the valve seats. Before he purchased the car he researched the issue and found the valve seats in the 1973 Charger were already compatible with unleaded gas.

[JimK]

Is sounds like the pending regulation in the 1970's for unleaded fuel led manufacturers to get in front of the issue by planning for harder valve seats. In that same era or a little earlier, it sounds like American/Amoco figured out that deposits on the valves where the bigger culprit and harder valve seats may not have been as important as having cleaner gasoline for keeping the valves healthy in the long term. It leads me to think that the auto and petroleum industries may have eventually put us on the path to unleaded fuel because it was better, not because it was mandated. Had it gone that way, I wonder if we could have ended up with all cars using unleaded gas at an overall lower cost to all of us.