I have what I think is a 1988 Mercury 175hp Black Max, but I'm unable to locate a serial number. The paper sticker on the trim unit is unreadable, and the freeze plug on the block just says 175. I've searched the entire engine with a fine toothed comb..... but haven't found anything. Is there any other place I can look to find the number?<br /><br />Thanks<br /><br />Walt