RO30009 is a platinum plug for Crusader 8.1 engines. Somewhere I read that they had a 1000 hour rating, much like the 100,000 mile plugs in new cars. When I thought I had an engine miss I contacted Jerry's Marine (Crusader distributer 1-800-432-2231) in FTL and they supplied Denso/TJ14R-P15 plugs. Turned out to be the crankshaft position sensor and covered by a recall. My engines came with AC41-993 plugs when new. Capt. George
The owners manual indicates the plugs should be changed each year or at 100 hour intervals. The current plugs have been used for two seasons and have 80 hours.
The boat runs fine; I am wondering if changing the plugs at this time is a waste of time & money. The 1000 hour rating you mentioned would seem to indicate that it a waste.
The origional owner had the plugs changed every year.