RiverRat - that does not surprise me since the Lightning gearcase on the HO's is designed for higher mounting with lower water pickups. With the additional negative trim that most of the newer motors have, higher mounting is the norm and makes for a much more efficient running setup.
It sounds like the cavitation plate is well above the bottom of the boat. It seems like every year the manufacturers brag about more negative trim. They must do it in .01 degree increments, because I can't see much change from years ago. jim
With the motor trimmed all the way down, and the boat on plane (15-30ish), the water washes over the cavitation plate about half way back. With decent trim, you can see most/all of the cavitation plate. This is with a wedge as well.
I currently have a 17 pitch viper. Not totally sold on it, but I had someone else exchange the wrong props that I got a while back for some new ones, and evidently the dealer told him that the viper was a good choice, so he didn't get the rebel that I requested. I have a 19 pitch rebel in my garage waiting to be tested.
Greg: Perhaps these Hydrodyne 18's turn into bucking broncos at 70 MPH - I don't know. I can tell you that at 62 MPH the boat is silky smooth with not even a hint of porpoise or chine walk when properly trimmed. My brother's 17' Glastron, on the other hand, is downright dangerous in chine walk when it is trimmed up to obtain a top end of 48 MPH WOT. We're nervous about letting our teenagers drive it because of its poor behavior in this regard. We've tried moving the engine up and down, we've tried adjustable trim tabs on the back of the hull, we've tried different props. As a point of fact, the boat is not a good design and it is dangerous at even modest speeds if you introduce any amount of trim. You need only to look at the short, deep hull with its V pad and rear mounted fuel tank to see why it behaves the way it does at speed. You don't need to be a marine engineer to see the problem. Not so with a properly set up Hydrodyne. I've heard it said that these 18' Dynes are not good performers at higher speeds. I know that their purpose is waterskiing (actually - I'm not even sure that's true because I think the hull was originally designed as a race hull). I don't know what the magic speed is for these boats where they start to misbehave. Perhaps they behave worse at high speed when twin rigged. I may buy a high pitch prop down the road sometime just to play around and see where the boat starts to act up. It is certainly fine at 62 MPH. Not a twitch, even in less than smooth water. You can steer with one finger at that speed.
The fix for the Glastron is pretty simple. Keep going down in pitch until it cannot achieve the problem speed. It will pull harder too. Add a wedge for low speed planing help. Have I ever said that before? Do not put one of those cavitation plate fins on it. If you want to go really fast in the Dyne you need to get a jackplate with about 10 or more inches of set back and a sportmaster lower unit. Raise the motor until the bullet nose is about even with the drain hole and get a surface piercing prop like about a 30 or 32 inch pitch chopper or lightening ET and get it on, and good luck! That should get you 90 or better provided you send your electronics out and have the rev limiter removed, and if you can hang with it. Anything short of that is just messing around IMO. If that is not fast enough, I will get you a great deal on a 300XS. :smash: opcorn: :drink: 8O 8) :lol: :yahoo: :wave: Let the big dog hunt!!! jim
Or, maybe this standup guy will let you drive his boat: http://vids.myspace.com/index.cfm?fusea ... 1743934888 jim :yahoo:
Jim That all sounds good... for a conservative Dyner. I'm planning to remove the Merc and install a Pratt PT6 on the back. If the boat does not disasssemble itself it ain't fast enough. My skiiers want to really move. Speaking of which, my brother wanted me to pull him wide open but we never got there - he panicked and hit the "thumbs down" signal before I ever really got going. He claims that the engine was starting to make a small rooster tail that was going over the top of his ski. I dunno. I was looking forward... he was aft.... :drink: OK everyone - we're seasoned professionals here, don't try this at home (for the record). :good:
If any of you are seriously considering going fast in this round bottom boat, you need to read the thread below. This man has gone fast in a round bottom boat. He has been fished out of the water at least twice and I think three times. One two of the occasions he has had water in his lungs. The last time he was in the hospital for months and may still be there. He will probably do it again. He has so many injuries that I had to stop reading. http://forums.screamandfly.com/forums/s ... t=joe+ward Mark, there is a guy on the west Coast named Mike Bemis. He built the swivel ski that I designed for my daughter. He specialises in race skis and holds some records I believe. You can find him with a Google search. He builds beautiful laminated skiis. edit: here you go: http://www.boats.com/news-reviews/artic ... l?lid=2004 jim
