Atlas Jackplates

[kerno]

The idea of going over a hundred in an open boat sounds completely nuts, but is probably one of the most fun things you'll ever do. I found the area between about 90 and 125 to be the most impressive and a couple good passes on early morning water can be enough of an adrenaline rush that you'll still be shaky and hour later. Over a buck and a quarter, it just staples the goggles harder on you face, but does not feel much different. It is the magic point where the boat is high enough that you can't feel the water anymore that you'll be grinning like an idiot or scared sh*tless!

You're talking about doing this with a big single on a jackplate, so based on my experience, you're going to find that your best speed is going to be made with the engine so high that almost the entire bullet is out of the water and you'll be running on only about 40 percent of the prop diameter. You'll have the plate down for the leave, bringing it up as you go. You may work the trim in the early part of the pass, but the big end is mostly jackplate. The word "rake" is really going to be a part of your prop vocabulary!

Here's the spooky part: As the engine gets higher, your ability to steer the boat gets lower. With twins, you steer with the throttle, but on a single, the blades are trying to drag the tail of the boat sideways, while the prop thrust is pushing forward. So, as you go faster, you have to correct by adding more steering and you add it gradually as you go. But the boat will slow down a lot faster than it will accelerate and that's where it get tricky. If you back off too fast, the corrections you've made will become over corrections and the boat will try to jink to the side. It is one thing if you are fighting just the lack of steering from having so little prop and lower unit in the water and another thing if the motor is adding to the fun by flexing the 14 inches of stacked plates.

I've had great luck with the Stainless Marine plates because I think they are the toughest ones out there. If I were rigging your boat and faced with the engine sitting in a recess in the transom, I'd make a welded and heat treated aluminum spacer "bracket" that is 8 inches thick and has a 3/4 plate on the transom that comes close to matching the transom recess. It would have a large hole cut out in the center to bring the lines through but would have beefy side plates supporting a gusseted 3/4 plate that the jack plate bolts to. It would not be movable or adjustable. Once you get it fitted to the hull, it should be powdercoated and go on with 4200 and at least 8 bolts to distribute the load. Th top half of the plate is under tension. Think of clamping the bracket in a giant vise and hanging the boat from it. That's what happens at speed. The bottom of the bracket is tying to push through the transom and the top is trying to pull loose. So, lotsa bolts at the top, not so many at the bottom. You'll also want a doubler plate inside the transom to distribute the load of the bolts. If the transom plate is 3/4, the doubler should be as well. To me, this kind of speed requires a foot throttle. Your arms can't react fast enough with the long throw of a lever and you'll need both hands for steering, trim and jackplate. Both he trim and the jackplate should be on paddles behind the wheel. Wheel mounted switches are common, but if you have the wheel turned 180, you can hit the wrong switch. I've tried foot switches for trim and jack, but while your right foot works great for the gas, teaching your left foot to work switches does not work well if you have to think about what you want it to do.

You'll need some personal rigging as well. Ordinary jackets don't cut it at speed. You don't need a chute jacket, but you are going to want at least a Lifeline jacket rated for 100 mph. They don't come apart on impact and they have crotch straps so they don't come off over your head. I've got several of them, so if you wear about a 46 jacket, I can help.

I understand your dislike of the stacked plates. I had a similar problem, on my Talon and I solved it by making the engine mounting arms and the jackplate all one unit. I used the cylinder and the slide bearings of Stainless Marine plates and machined everything out of the solid.

Edited November 26, 2009 by kerno

[Z22]

Porta makes a great JP, that can handle high HPs.

See: http://www.portaproducts.com/index.php?page=photo-gallery

[Ludicrous]

The idea of going over a hundred in an open boat sounds completely nuts, but is probably one of the most fun things you'll ever do. I found the area between about 90 and 125 to be the most impressive and a couple good passes on early morning water can be enough of an adrenaline rush that you'll still be shaky and hour later. Over a buck and a quarter, it just staples the goggles harder on you face, but does not feel much different. It is the magic point where the boat is high enough that you can't feel the water anymore that you'll be grinning like an idiot or scared sh*tless!

You're talking about doing this with a big single on a jackplate, so based on my experience, you're going to find that your best speed is going to be made with the engine so high that almost the entire bullet is out of the water and you'll be running on only about 40 percent of the prop diameter. You'll have the plate down for the leave, bringing it up as you go. You may work the trim in the early part of the pass, but the big end is mostly jackplate. The word "rake" is really going to be a part of your prop vocabulary!

Here's the spooky part: As the engine gets higher, your ability to steer the boat gets lower. With twins, you steer with the throttle, but on a single, the blades are trying to drag the tail of the boat sideways, while the prop thrust is pushing forward. So, as you go faster, you have to correct by adding more steering and you add it gradually as you go. But the boat will slow down a lot faster than it will accelerate and that's where it get tricky. If you back off too fast, the corrections you've made will become over corrections and the boat will try to jink to the side. It is one thing if you are fighting just the lack of steering from having so little prop and lower unit in the water and another thing if the motor is adding to the fun by flexing the 14 inches of stacked plates.

I've had great luck with the Stainless Marine plates because I think they are the toughest ones out there. If I were rigging your boat and faced with the engine sitting in a recess in the transom, I'd make a welded and heat treated aluminum spacer "bracket" that is 8 inches thick and has a 3/4 plate on the transom that comes close to matching the transom recess. It would have a large hole cut out in the center to bring the lines through but would have beefy side plates supporting a gusseted 3/4 plate that the jack plate bolts to. It would not be movable or adjustable. Once you get it fitted to the hull, it should be powdercoated and go on with 4200 and at least 8 bolts to distribute the load. Th top half of the plate is under tension. Think of clamping the bracket in a giant vise and hanging the boat from it. That's what happens at speed. The bottom of the bracket is tying to push through the transom and the top is trying to pull loose. So, lotsa bolts at the top, not so many at the bottom. You'll also want a doubler plate inside the transom to distribute the load of the bolts. If the transom plate is 3/4, the doubler should be as well. To me, this kind of speed requires a foot throttle. Your arms can't react fast enough with the long throw of a lever and you'll need both hands for steering, trim and jackplate. Both he trim and the jackplate should be on paddles behind the wheel. Wheel mounted switches are common, but if you have the wheel turned 180, you can hit the wrong switch. I've tried foot switches for trim and jack, but while your right foot works great for the gas, teaching your left foot to work switches does not work well if you have to think about what you want it to do.

You'll need some personal rigging as well. Ordinary jackets don't cut it at speed. You don't need a chute jacket, but you are going to want at least a Lifeline jacket rated for 100 mph. They don't come apart on impact and they have crotch straps so they don't come off over your head. I've got several of them, so if you wear about a 46 jacket, I can help.

I understand your dislike of the stacked plates. I had a similar problem, on my Talon and I solved it by making the engine mounting arms and the jackplate all one unit. I used the cylinder and the slide bearings of Stainless Marine plates and machined everything out of the solid.

That bracket is very trick. I'll have to measure but I think I wear a 48+ vest. Do you really think I need a chute vest? Here's what I've been looking at:

http://www.lifelinejackets.com/no-chute_jackets.cfm

Getting close to picking the hull. think I'm going for the Stroker hull that needs someone to "save" it from the current owner. It would be a 6 month project but I'd like to go through every inch, wire etc. I'll be sure to involve you in it!