the optis use the expensive plugs, and $15 is for the cheap ones. Mercury oiling systems are not the best, they aren't the worse either, but after they get some age on them, I don't like to contiue to run them. The oil pump is driven by a plastic gear on the crankshaft. the plastic gear can fail and cause oiling problems. Ive also seen the clear plastic hose that feeds thr oil to and from the pump crack, it will pump the oil insode the cowl and never set the oil alarm till all the oil is gone, because the pump is still spining. Its not that hard to disconnect the system. the oil tank in my 79 was under teh hatch in the splash well. If you had to access the batteries or oil tank while in hte water, you can risk lettingwater into the bilge, especially if you are in rough water. i moved the batteries into the fish box area under the floor to allow access from inside the boat.
http://www.wellcraftv20.com/communit...ead.php?t=5000 jeres teh link showing where I put them, haven't finished the job, still trying to finish the Glastron