Re: hmm...fat guys?
Heres the summary the way I see it:<br /><br />Old (inefficient) hull design, fairly heavy 18 foot deep V boat that may have some water soaked into the structure (heavy,) 120 hp motor, struggles to get an adult pound slalomer out of the water, turning 4,500 rpms (on an inaccurate boat tach) at 30mph (on an innacurate boat speedo.) <br /><br />In my mind that pretty well describes exactly what you can expect from this setup, and I doubt you'll do any better.<br /><br />The only thing that I agree doesn't add up is the 21 pitch prop. I just don't think that's possible. Unless, as was already mentioned, it's a real narrow diameter. OR...and nobody has mentioned this yet, but....maybe that 21 pitch prop has been rebuilt and repitched by a prop builder, so it's no longer a 21 but you don't know it.<br /><br />You don't want to lose any top speed because you need at least 30 to slalom, and you don't want to spin much beyond your 4,500, so I wouldn't change anything other than maybe give it a good tuneup if you haven't already, get every last pound out of weight and junk of that boat that's not necessary, and most importantly check your rpms with a real tach, and your speed with a GPS...you might be surprised to find out your numbers are completely different from what you think they are. And don't forget that this is a rather old, underpowered boat to be asking to do this type of work.<br /><br />Not sure how heavy your skiier was, or how long or wide his/her ski was, but that's critical as well. Put a fat man on a short ski (such as one ski off of a "combo" setup that so many people use, which are always too short and narrow to effectively slalom), and he'll be the perfect water drinking anchor. Put that same fat man on a quality 70 inch shaped slalom, and he might just pop right out of the water. And how many people did you have on the boat when he was skiing? 4? WAY too many. Get some people to sit on shore while he skis. All I'm saying in way too many words is that there's a LOT of variables here to consider that may go beyond the boat.<br /><br />For comparison's sake, my 18 foot 1992 Rinker with a 115 hp mercruiser has a 14 1/2 x 17 pitch prop, WOT turns 4,500 at 37 mph (calibrated tach and gps speed), and it also struggles a bit, but manages to get an adult 190 lb slalomer (me) out of the water on a 69 inch HO Charger, which is a fairly wide ski. I've never tried it with more that 3 people on board, and I really don't think I want to. My Rinker is not a very deep V, and is probably a little lighter boat than yours. The reality is simply that 4 cylinder runabouts are not good ski boats, but they work in a pinch if your skiers don't mind the drag & drink method.<br /><br />Good luck, and enjoy!
<br /><br />Butch A.