89 43L burning valves

Last year my boat had no compr

Last year my boat had no compression in one hole. I put the boat away for a few months and finally had some time to pull the head off. I found that half of one valve was burnt off. I had the head re-done and the boat ran for 6-7 trips and now I have another burnt valve on the same side. Any info or experience with this?

"Ayuh,....

That's Usual

"Ayuh,....

That's Usually caused by Detonation....

Detonation can be caused by several things,...
A few are,..
Motor running Lean...
Motor Not able to achieve the recommended RPMs at WOT...
Wrong Timing...
Bad Gas..."

"burnt valves says "lean c

"burnt valves says "lean condition". If no one has played with the carb recently, I would look for a vacuum leak on the intake or carb. If your boat has the heat tube type choke, that's a common place for leaks.
Brushing kerosene on and looking for smoke, or using the propane enrichment method can help find vacuum leaks.
Valves adjusted too tight also a way for valves to not seat properly and suffer guttering. partly open valve becomes subject to combustion flame like when you cut with a cutting torch- it superheats the valve and then blows material away"