I believe this topic has been discussed many times prior, however not in a direct approach in terms of actual originating boat design. IE: medium\large sailboats at production time.
The inclusion of an inboard diesel engine on larger sailboats has become a given. To exclude this version of auxilary power on a boat over 27 feet would raise eyebrows and flutter lips in contempt, as this has been established as the norm for larger sailboat design.
That said, can we look at the fundamental benefits and limitations of both, in an open minded analysis of coastal cruising boats. Extracting vessels specifically designed for offshore use which would be designed to expect heavy seas.
Speed:
An outboard can be tilted up, removing the prop, shaft and skeg from the water flow. This can increase speed as much as a half knot depending on conditions and boat config.
With the inboard, even if you install a $1,000 folding prop you still have skeg and prop shaft drag.
Weight reduction would be significant, however it would move a slight amount to the transom, which should be compensated for in the design\ballast, etc.
Dead battery:
If all batteries should be rendered incapable of starting the engine, a (up to about 20hp) outboard can be pull started, thereby returning propulsion and charging the batteries.
Tangles:
Prop tangles with traps and seaweed, etc, can slow or even stop an inboard. The latter of which may require a dive to untangle. An outboard can be tilted and the foul easily cleared.
Vector thrust:
An inboard is dependent upon the rudder for steerage, sans some prop walk in some circumstances which can be used. However an outboard, while usually locked and stationary and using the rudder in the same fashion as an inboard, can be unlocked and vector power used to drive a large sailboat like a dinghy, getting in and out of tight situations safely.
Odors:
The inside of many inboard vessels reeks of diesel. The inside of an outboard powered boat smells like rum teak oil.
Maintenance access and cost:
On an outboard, the cooling system (+no risers), exhaust, oil, fuel hoses, shaft, zincs, etc are outside and easy to access. Annual service on a 20hp Honda is $183.
Safety:
With an outboard, there are no oil, coolant, fuel or exhaust leaks that can escape into the bilge or cabin. Also, no shaft packing to leak. Gasoline can be raised as a safety issue, however with the tank located outside the cabin, IE: under a cockpit seat in a fuel tank-designed lazzerette containing a 12 gallon tank, vapor and explosion risk becomes minimal, much less than the combination of common inboard safety issues listed above.
Noise:
With a quiet engine on the transom, cabin noise is reduced to a low rumble, and not the tractor racket heard in many diesel powered boats.
Initial cost:
Installing an outboard in lieu of inboard diesel would save about $10,000 off the boat's price. This would likely reduce the resale amount by that much of course, but this fact is irrelevant.
Appearance:
An outboard generally spoils the lines of the transom. A minor Aesthetics problem when compared to the advantages.
Sea State:
As mentioned previously, the outboard concept applies to coastal vessels. That said, an outboard can very easily exit the water depending on seastate, causing an overev at worst or a slowing of momentum. This is more or less reserved for a boat that is stopped or is traveling slowly in short frequency high chop. Once momentum is gained, the boat plows ahead and keeps the motor in the water unless the seas are abnormal for coastal conditions. Also, if the seas are rough you can predict that the wind will be good as well, in which case the sails would make better engines. In any case if the weather is predicted to be reminiscent of offshore storms, a coastal boat skipper should probaly stay in the harbor anyway.
Conclusion:
If traveling offshore, there is nothing more reassuring than the steady cackling of a diesel engine, not to mention the obvious benefit of a reliably good bite in heavy weather. However if I were ordering a sailboat for coastal cruising, I would seriously investigate opting for an outboard, even in a larger sailing vessel. For example if I ordered a cat 28, 309 or even a 320, I would consider having a 20hp long shaft installed, if they were willing to do so.
Please let me know if this makes sense or if I am a nut case.
The inclusion of an inboard diesel engine on larger sailboats has become a given. To exclude this version of auxilary power on a boat over 27 feet would raise eyebrows and flutter lips in contempt, as this has been established as the norm for larger sailboat design.
That said, can we look at the fundamental benefits and limitations of both, in an open minded analysis of coastal cruising boats. Extracting vessels specifically designed for offshore use which would be designed to expect heavy seas.
Speed:
An outboard can be tilted up, removing the prop, shaft and skeg from the water flow. This can increase speed as much as a half knot depending on conditions and boat config.
With the inboard, even if you install a $1,000 folding prop you still have skeg and prop shaft drag.
Weight reduction would be significant, however it would move a slight amount to the transom, which should be compensated for in the design\ballast, etc.
Dead battery:
If all batteries should be rendered incapable of starting the engine, a (up to about 20hp) outboard can be pull started, thereby returning propulsion and charging the batteries.
Tangles:
Prop tangles with traps and seaweed, etc, can slow or even stop an inboard. The latter of which may require a dive to untangle. An outboard can be tilted and the foul easily cleared.
Vector thrust:
An inboard is dependent upon the rudder for steerage, sans some prop walk in some circumstances which can be used. However an outboard, while usually locked and stationary and using the rudder in the same fashion as an inboard, can be unlocked and vector power used to drive a large sailboat like a dinghy, getting in and out of tight situations safely.
Odors:
The inside of many inboard vessels reeks of diesel. The inside of an outboard powered boat smells like rum teak oil.
Maintenance access and cost:
On an outboard, the cooling system (+no risers), exhaust, oil, fuel hoses, shaft, zincs, etc are outside and easy to access. Annual service on a 20hp Honda is $183.
Safety:
With an outboard, there are no oil, coolant, fuel or exhaust leaks that can escape into the bilge or cabin. Also, no shaft packing to leak. Gasoline can be raised as a safety issue, however with the tank located outside the cabin, IE: under a cockpit seat in a fuel tank-designed lazzerette containing a 12 gallon tank, vapor and explosion risk becomes minimal, much less than the combination of common inboard safety issues listed above.
Noise:
With a quiet engine on the transom, cabin noise is reduced to a low rumble, and not the tractor racket heard in many diesel powered boats.
Initial cost:
Installing an outboard in lieu of inboard diesel would save about $10,000 off the boat's price. This would likely reduce the resale amount by that much of course, but this fact is irrelevant.
Appearance:
An outboard generally spoils the lines of the transom. A minor Aesthetics problem when compared to the advantages.
Sea State:
As mentioned previously, the outboard concept applies to coastal vessels. That said, an outboard can very easily exit the water depending on seastate, causing an overev at worst or a slowing of momentum. This is more or less reserved for a boat that is stopped or is traveling slowly in short frequency high chop. Once momentum is gained, the boat plows ahead and keeps the motor in the water unless the seas are abnormal for coastal conditions. Also, if the seas are rough you can predict that the wind will be good as well, in which case the sails would make better engines. In any case if the weather is predicted to be reminiscent of offshore storms, a coastal boat skipper should probaly stay in the harbor anyway.
Conclusion:
If traveling offshore, there is nothing more reassuring than the steady cackling of a diesel engine, not to mention the obvious benefit of a reliably good bite in heavy weather. However if I were ordering a sailboat for coastal cruising, I would seriously investigate opting for an outboard, even in a larger sailing vessel. For example if I ordered a cat 28, 309 or even a 320, I would consider having a 20hp long shaft installed, if they were willing to do so.
Please let me know if this makes sense or if I am a nut case.
