My friend's 1996 Bayliner with the 181 ci GM 4 cylinder engine lost most of its oil. I discovered that the oil filter had three holes in it resulting from a rusted housing (talk about good PM). Since the engine had lost a significant amount of oil, I decided to pull the engine and check the lower end bearings for heat or wear damage. Luckily, he had shut the engine off when he heard the valves begin to clatter and the bearings showed no signs of abnormal wear. While preparing to reinstall the engine in the boat, I discovered rust holes in the oil pressure sending unit. I purchased a new one from my local auto parts store. The problem is that when I start the engine, the oil pressure gauge immediately pegs to 80+ psi. I teed a direct reading gauge into the system and it reads between 40 and 45 psi which is more of a normal reading. I exhanged the sending unit for another one and it does the same thing. I recall having a similar problem with an oil sending unit purchased at the same store on another boat a few years ago. Is there something I don't know about oil sending units? Does a marine application require a special oil sending unit? Any insight will be appreciated. I am about at my wits end.
