Newby.Engine power to sail boat speed

[mitiempo]

Are you thinking diesel?

You would need to marinize it - heat exchanger, marine transmission, and other bits and pieces.

 

[Richard D]

Yes,I know the bits nec but you could use a lot parts from other instalations, a heat exchanger is a heat exchanger not difficult in comparison to other stuff I have done. Dont have a boat yet , would love to find the right boat with a dead engine.

Richard

 

[Tranona]

Yes,I know the bits nec but you could use a lot parts from other instalations, a heat exchanger is a heat exchanger not difficult in comparison to other stuff I have done. Dont have a boat yet , would love to find the right boat with a dead engine.

Richard

There is a huge industry producing marinised engines. They have refined it to the point where DIY type conversions ahve diappeared. If the boat you buy has a dead engine there is a choice of at least half a dozen perfectly satisfactory engines, meeting all the latest regs available off the shelf.

Don't reinvent the wheel! The past is littered with people and major engine builders who have tried buildinbg marine engines and withdrawn - VW being the latest (for the second time of trying).

 

[rob2]

I always fancied the earlier Citroen diesels, when they were still being built with all the extras - beefed up bearings and extra lubrication, etc. The small 1500(?) van engine was around 30hp, wasn't it? The main downside to marinising one would be the lack of availability of a water cooled exhaust manifold.

The lack of airflow over the engine can be a problem - I've known very well respected motor manufacturers who have forgotten this and ended up with spontaneous engine fires under the bonnet! When I used a ZX for towing, there was a deflector plate fitted to increase the airflow over the engine. One manufacturer tucked the aircon compressor under the exhaust manifold and wondered why it never worked (even if it wasn't burning). In a tight installation like a sailing boat, an automotive engine may run into problems, whereas most small boat engines are based on industrial engines designed to run flat out, indefinitely in a small box with no airflow - hence relatively low power output.

Rob.

 

[mitiempo]

Yes, many are really marinized long lived tractor engines.

 

[William_H]

Boat diesels

One thing not mentioned is the number of cylinders.
This is of importance because a small boat say under 30 ft might only need 12 hP or less to do the job. However while this can be achieved with a single cylinder diesel the noise/ vibration can be horrible.
Far better 2 or 3 cylinders which is much more expensive and for the required horsepower tends to be under rated. But worth the cost for the smoothness.
As said the "hull speed" is a point where the relationship of power versus speed has gone from nearly linear to exponential. The formular is more useful to compare the effect added hull lenght makes than to determine an actual speed.
Sailing boats often exceed the "hull speed" by a lot and will go a lot faster under sail than motor. This because powert from the wind is not expensive. olewill