1985 12 Meter questions
 

My father has this boat, not a lot of previous history on it, but have fixed a lot of stringer damage and bulkheads in the cabin/cockpit and now its time for some new power. It was running basically HP500's around 525hp or so with SSM #3's (19 spline small shaft) turning 16.5X24 props right around 5k WOT hitting only mid 60's. We are in the process of building some 540's that we plan to dyno out around 680/690 HP. I know these props are getting harder to find and we will also plan to spin around the 5500 rpm range but do you guys think we will still need to move up in prop? Suggestions? I'm not sure of the drive ratio, cannot see anything stamped in the upper. I also wanted to ask, after i pulled the props to check size I noticed the starboard propshaft outter seal was missing? I'm not fimiliar with these drives at all, seeing the pics, can anyone tell me what that seal is? Does the propshaft need to come out to replace, or does it sline onto the shaft and butt up to the drive housing? Also, anyone know what kind of speed numbers we should expect running high 600 hp with these drives? Sorry for all the questions, really appreciate any input anyone might have. Thanks! Mike

a big yes to needing that seal,outer seal keeps water out inner seal keeps lube in,dont run until you get resealed..

my dad has a 88 12 meter he bought new. then it had 650's & #3 drives & would go 80

I was thinking high 70's or so, would be very happy with 80 though:) These boats are tanks!