Geo, that's the big fear. That I'll be happily crusing along with a skier in tow, and POP! Big time steam everywhere, and river water in the bedroom.
They are going in streight, and are flush with the block, but the others are about 1/16-3/32 recessed. I can't say I really cleaned the block up much, other than to just run my finger around the hole, and it felt pretty good. I had heard to try and put RTV on it, but the RTV just made it so slippery that after dropping it in the bilge a few times, I said the heck with that and stopped trying to put it on. They are metal, and about 1/4" dished, with a good size rim on them. Got them from the Ford dealer, because my marina couldn't source any from OMC. It pains me that marinized Fords were not popular, and hence parts availability is nill now. I'm told my exhaust manifolds are like gold. This engine has about 325 hours on it, never seen salt, and looks like new. Being 13 years old it's in really good shape. I think the original plugs were brass or bronze. I was afraid to re-use them even though they looked great. Doug, I think these are opposite what the IDI's have on them. I think you have to hit the edges and not the center.