i'm pretty new to owning a boat and the guy that i bought my boat from said that "his lower unit fell off while on the water" and that the one on there currently is a newish one....personally, i think he smacked a rock real good with it and need to replace it. but with all that silliness aside, i have a question about the unit. it's on a 225 '99 opti and i noticed that not only does it have water intakes on the sides...but it also has 4 holes on the nose of the gear case as well. i'm assuming that this is a water intake as well. the reason why i'm asking is because i'm thinking about getting a jack plate and i don't want to have issues with low water pressure. i'll need to install a water pressure guage along with the jackplate......what PSI should the opti be running at?? any info would be GREAT thanks 