I have a Bayliner with 3.0 mercruiser. The engine that was in it was a 2005 model serial number 0w342092. We had to replace engine due to not winterizing it. We ordered rebuilt long block online. We told them what we had and what we were needing. Had to get a new manifold, carburetor, and starter. Got engine assembled and installed in boat. Got engine running and timing set. Took the boat out this last weekend and it ran good for half an hour then started knocking and went dead. I pulled sparks plugs out and noticed only #1 plug was bent from contact with piston. Spark plug mr43lts. Which is the same plug that was in original engine. The long block didn’t come with new plugs. I just got old plug number and got new ones to put in there. I found serial number of long block is 624414pm (that is what invoice on paper has written on it). After research the long block I got seems to require the shorter plugs. I’m not 100% sure of that though. The best I can tell from the past 4 hours of research is the long block is a mid 80’s model. And has a different head that the original 2005 engine. Is there just two dimensions of spark plugs for the 3.0? Short or long? Also the timing spec for original engine is 2 atdc. Do I need to set timing different for this different long block? Thanks
