Bob Bourget2
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- Apr 25, 2011
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Lots of questions about this issue so...
Let's start HERE......
"How come it pulls one way so HARD?" Prop torque is dealt with by engine trim angle, set-back, g'case design, prop choice, and hull design. Working within the design parameters of cost-control, the engineers can only do their best to design a g'case and achieve "balance". Lets face it. We want SUPERB handling whether we have a 20 mph jon-boat or an 80 mph Nitro. Not an easy feat to accomplish. We deal with it by set-up, and operator awareness / education.
Rule of thumb for trim tab adjustment: If it pulls to the right, turn the trailing edge of the trim tab to the right. Sounds backwards, but in theory, the truth. If it pulls hard to the right, that means it is difficult to steer LEFT. By turning the tab trailing edge to the right, it tries to drive the g'case to the left, easing prop / steering torque. Got it? Memorize it.
Hi-perf applications: A different animal altogether. We are now throwing into the mix set-back, 250hp, jackplates, half-in, half-out, torque tabbed, afterplaned, solid mounts, dual cable....sheesh.....OK. Typically the faster the boat, the higher the engine height. To combat steering torque, there are skeg-mounted torque tabs that can be riveted on the starboard side of the skeg. Bob's Machine Shop has these available and they do work. Mercs own torque-master {wonder why they call it that?}, has a built-in camber {or torque-tab}, to counteract the tremendous paddle-wheel affect surfacing props bring. G'case innards are heavy-duty to withstand surfacing operation.
Set-back. I've touched on this before and you all know where I stand. TYPICALLY, the more set-back, the better the weight distribution, LESS trim is needed to achieve top-end, and prop torque is minimized. When you are pushing a motor through the water at extreme trim angles, steering torque is unbearable.
Different types of systems:
1. "Cable system". A basic push-pull cable {or two} driven by either a rack or rotary helm. YOU are the engine that will steer the boat. YES, you'll get steering torque, yes, if you adjust trim, you'll find the sweet spot. It may not be the fastest trim setting, but you'll find it. There are no-feedback helms available that assist with a reduction in torque.
2. "Hydraulic". Still "mechanical", all this system does is substitute fluid dynamics for a cable. YES, it is slightly easier to steer. Will it eliminate prop torque? NO. It will minimize it.
3. "Power Steering". Ok, now we're talkin'. Available on the Verado L4 {150-200}, and standard on L6 {225-350}, it has an electric motor in conjunction with hydraulics to give you car-like assist. Yes, it works. I drove a 75MPH nitro the other day HOLDING THE STEERING WHEEL HUB WITH MY HAND. Don't try this at home folks.....:blink:
So, they're 'ya have it.
Let's start HERE......
"How come it pulls one way so HARD?" Prop torque is dealt with by engine trim angle, set-back, g'case design, prop choice, and hull design. Working within the design parameters of cost-control, the engineers can only do their best to design a g'case and achieve "balance". Lets face it. We want SUPERB handling whether we have a 20 mph jon-boat or an 80 mph Nitro. Not an easy feat to accomplish. We deal with it by set-up, and operator awareness / education.
Rule of thumb for trim tab adjustment: If it pulls to the right, turn the trailing edge of the trim tab to the right. Sounds backwards, but in theory, the truth. If it pulls hard to the right, that means it is difficult to steer LEFT. By turning the tab trailing edge to the right, it tries to drive the g'case to the left, easing prop / steering torque. Got it? Memorize it.
Hi-perf applications: A different animal altogether. We are now throwing into the mix set-back, 250hp, jackplates, half-in, half-out, torque tabbed, afterplaned, solid mounts, dual cable....sheesh.....OK. Typically the faster the boat, the higher the engine height. To combat steering torque, there are skeg-mounted torque tabs that can be riveted on the starboard side of the skeg. Bob's Machine Shop has these available and they do work. Mercs own torque-master {wonder why they call it that?}, has a built-in camber {or torque-tab}, to counteract the tremendous paddle-wheel affect surfacing props bring. G'case innards are heavy-duty to withstand surfacing operation.
Set-back. I've touched on this before and you all know where I stand. TYPICALLY, the more set-back, the better the weight distribution, LESS trim is needed to achieve top-end, and prop torque is minimized. When you are pushing a motor through the water at extreme trim angles, steering torque is unbearable.
Different types of systems:
1. "Cable system". A basic push-pull cable {or two} driven by either a rack or rotary helm. YOU are the engine that will steer the boat. YES, you'll get steering torque, yes, if you adjust trim, you'll find the sweet spot. It may not be the fastest trim setting, but you'll find it. There are no-feedback helms available that assist with a reduction in torque.
2. "Hydraulic". Still "mechanical", all this system does is substitute fluid dynamics for a cable. YES, it is slightly easier to steer. Will it eliminate prop torque? NO. It will minimize it.
3. "Power Steering". Ok, now we're talkin'. Available on the Verado L4 {150-200}, and standard on L6 {225-350}, it has an electric motor in conjunction with hydraulics to give you car-like assist. Yes, it works. I drove a 75MPH nitro the other day HOLDING THE STEERING WHEEL HUB WITH MY HAND. Don't try this at home folks.....:blink:
So, they're 'ya have it.
