03-08-2013, 01:04 PM
Ok, I'm posting more information.
I have sold several IPS boats over the years and there seems to be a lot of confusion or misinformation out there regarding IPS. Below is some good information for IPS owners or those thinking of purchasing IPS.
1) IPS Drives do not turn 360 degrees. The drive units actually only turn 13 degrees each way from center for a total of 26 degrees of motion. At planning speeds, the computer may limit how far the drives will turn based on speed. When using the Joy Stick, the drives turn inward 13 degrees each. When you push the Joy Stick forward, both drives go into forward gear and push the boat forward. When you pull the stick back, it puts both drives in reverse. If you push the stick sideways, it puts one drive in fwd and one in reverse and adjusts the RPMs accordingly. Because the drives are angled inward the thrust is vectored sideways pushing the vessel sideways. If you turn the top of the Joy Stick, the drives will center and one engine goes into fwd and one in reverse in order to rotate the vessel. Combinations are where things get complicated and the computer knows what to do!
2) IPS 500s are not 500 HP each. IPS 500s are actually 370 HP each. Why do they use the number 500? If you where to build the same vessel with traditional straight inboards, it would take approximately twin 500 HP engines to push the vessel to similar speeds, as the IPS is capable of with less HP. That is why IPS is more fuel-efficient as it can push a vessel using less HP. The reason for this is complicated, but I'll try to simplify. a) The thrust angle of IPS is parallel with the hull bottom. Nearly 100% of the thrust is used to push the vessel forward. Inboards have shaft angles from 8 to 12 degrees. Thrust is wasted trying to push the vessel upward. b) Drag is another reason why IPS is more efficient. IPS drives do not have any exposed shafts spinning through the water creating drag. A traditional inboard shaft spinning at between 1000 and 3000 RPM running through the water at 8 to 12 degrees creates tremendous drag. C) IPS uses forward facing dual props that spin in opposite directions. Duo props are more efficient than a single prop. There is a certain amount of slippage with a single prop that a duo prop reduces. The forward facing props are also more efficient. The props bite clean water that has not been disturbed by passing by a drive unit or strut before entering the props. Overall, IPS is approximately 15 to 25% more efficient than a traditional inboard of similar size and weight.
3) There are not right and left hand IPS drives. The engines and drives are identical Port and Stbd from a rotation standpoint. Because the drives are duo props with counter rotating propellers, torque steering is eliminated. Both aft 4-bladed props are identical and interchangeable just as the forward 3-bladed props are.
4) IPS is a complicated system; however, it also eliminates many components found on traditional inboards. The IPS drives take the place of the following components: Transmissions, Shaft Logs, Mufflers, Hydraulic Steering Ram and Tie Bar, Rudders, Struts, Engine Raw Water Intakes and Exhaust piping and outlets. While drive service is expensive, if you added up service on all of the traditional inboard components, totals are likely similar.
5) IPS drives do not break off during soft to medium groundings. Yes, IPS units do have a catastrophic shear point built into them for safety reason, but unless you ram an immovable object at a high rate of speed, the drives are likely to remain attached to the bottom. The shear point is built-in to keep from ripping the bottom of the boat out and sinking the vessel. Inboards do not have this safety feature. Hard grounding an inboard will likely result in ripping the strut out of the bottom of the boat or pushing it up into the vessel, either way, hard grounding is going to cause severe damage.
6) Forward facing props are more susceptible to damage - This is not really true when comparing it to a traditional planning inboard. If you touch the bottom , the first thing to hit with either set up is most likely the props. IPS Props and shafts are usually less expensive to replace and repair than traditional inboard components. I/Os and Zeus drives to have some added security of a skeg and drive unit in front of the props, but if you ground, you are still going to do prop damage. 6 of one and have dozen of the other!
7) IPS vessels are more susceptible to overloading than traditional inboards. They are also more susceptible to marine growth and dirty bottoms from a performance standpoint. The reason for this is IPS props are smaller diameter and spin at higher RPMs than their traditional inboard counterparts. Make sure you use the proper coatings on the props (do not use traditional bottom paint on the props - it will not stick and it creates too much drag). Prop Speed is an acceptable coating and there are other equivalent coatings available. Any tiny growth on the props will likely drop your speed by several knots. If you tow a larger tender behind your IPS vessel, you may have to change your props to accommodate the additional drag and loading to ensure your engines are not overloaded. Towing may also require adding drive oil coolers to keep the drives from overheating.
I do like the Volvo IPS system. It is much more efficient and comes with better high-speed handling and of course, the joystick makes amateurs look like pros when docking. Traditional inboards still have their place in the yacht market, but eventually as the technology advances and the drive units get bigger and more efficient, the traditional inboards will slowly cease to exist.
I have sold several IPS boats over the years and there seems to be a lot of confusion or misinformation out there regarding IPS. Below is some good information for IPS owners or those thinking of purchasing IPS.
1) IPS Drives do not turn 360 degrees. The drive units actually only turn 13 degrees each way from center for a total of 26 degrees of motion. At planning speeds, the computer may limit how far the drives will turn based on speed. When using the Joy Stick, the drives turn inward 13 degrees each. When you push the Joy Stick forward, both drives go into forward gear and push the boat forward. When you pull the stick back, it puts both drives in reverse. If you push the stick sideways, it puts one drive in fwd and one in reverse and adjusts the RPMs accordingly. Because the drives are angled inward the thrust is vectored sideways pushing the vessel sideways. If you turn the top of the Joy Stick, the drives will center and one engine goes into fwd and one in reverse in order to rotate the vessel. Combinations are where things get complicated and the computer knows what to do!
2) IPS 500s are not 500 HP each. IPS 500s are actually 370 HP each. Why do they use the number 500? If you where to build the same vessel with traditional straight inboards, it would take approximately twin 500 HP engines to push the vessel to similar speeds, as the IPS is capable of with less HP. That is why IPS is more fuel-efficient as it can push a vessel using less HP. The reason for this is complicated, but I'll try to simplify. a) The thrust angle of IPS is parallel with the hull bottom. Nearly 100% of the thrust is used to push the vessel forward. Inboards have shaft angles from 8 to 12 degrees. Thrust is wasted trying to push the vessel upward. b) Drag is another reason why IPS is more efficient. IPS drives do not have any exposed shafts spinning through the water creating drag. A traditional inboard shaft spinning at between 1000 and 3000 RPM running through the water at 8 to 12 degrees creates tremendous drag. C) IPS uses forward facing dual props that spin in opposite directions. Duo props are more efficient than a single prop. There is a certain amount of slippage with a single prop that a duo prop reduces. The forward facing props are also more efficient. The props bite clean water that has not been disturbed by passing by a drive unit or strut before entering the props. Overall, IPS is approximately 15 to 25% more efficient than a traditional inboard of similar size and weight.
3) There are not right and left hand IPS drives. The engines and drives are identical Port and Stbd from a rotation standpoint. Because the drives are duo props with counter rotating propellers, torque steering is eliminated. Both aft 4-bladed props are identical and interchangeable just as the forward 3-bladed props are.
4) IPS is a complicated system; however, it also eliminates many components found on traditional inboards. The IPS drives take the place of the following components: Transmissions, Shaft Logs, Mufflers, Hydraulic Steering Ram and Tie Bar, Rudders, Struts, Engine Raw Water Intakes and Exhaust piping and outlets. While drive service is expensive, if you added up service on all of the traditional inboard components, totals are likely similar.
5) IPS drives do not break off during soft to medium groundings. Yes, IPS units do have a catastrophic shear point built into them for safety reason, but unless you ram an immovable object at a high rate of speed, the drives are likely to remain attached to the bottom. The shear point is built-in to keep from ripping the bottom of the boat out and sinking the vessel. Inboards do not have this safety feature. Hard grounding an inboard will likely result in ripping the strut out of the bottom of the boat or pushing it up into the vessel, either way, hard grounding is going to cause severe damage.
6) Forward facing props are more susceptible to damage - This is not really true when comparing it to a traditional planning inboard. If you touch the bottom , the first thing to hit with either set up is most likely the props. IPS Props and shafts are usually less expensive to replace and repair than traditional inboard components. I/Os and Zeus drives to have some added security of a skeg and drive unit in front of the props, but if you ground, you are still going to do prop damage. 6 of one and have dozen of the other!
7) IPS vessels are more susceptible to overloading than traditional inboards. They are also more susceptible to marine growth and dirty bottoms from a performance standpoint. The reason for this is IPS props are smaller diameter and spin at higher RPMs than their traditional inboard counterparts. Make sure you use the proper coatings on the props (do not use traditional bottom paint on the props - it will not stick and it creates too much drag). Prop Speed is an acceptable coating and there are other equivalent coatings available. Any tiny growth on the props will likely drop your speed by several knots. If you tow a larger tender behind your IPS vessel, you may have to change your props to accommodate the additional drag and loading to ensure your engines are not overloaded. Towing may also require adding drive oil coolers to keep the drives from overheating.
I do like the Volvo IPS system. It is much more efficient and comes with better high-speed handling and of course, the joystick makes amateurs look like pros when docking. Traditional inboards still have their place in the yacht market, but eventually as the technology advances and the drive units get bigger and more efficient, the traditional inboards will slowly cease to exist.
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