Re: What size spanner?
drop drill bits into the hole until you figure out size of hole. Then buy an armstrong adjustable face pin spanner (they are in stock at our local sears). Armstrongs are built solidly enough that they will not flex and wallow out your holes. I notice that you are in a saltwater location. If you can't get it to open using the right size wrench then drill out the holes to fit a mega-wrench with bigger, deeper posts. Heating the lip of cylinder with map gas to soften rubber seals is another salt water trick that really helps. However, sometimes the best way to rebuild a saltwater system is with a trash can.
