What size engine do I need for my Kingfisher 30 sailing yacht?

Question

The boat's 30ft LWL 25ft with 4000kg displacement. Maximum prop size is 13 in. Hull speed is about 7kts maximum. One engineer says I need to replace the old Watermota 33hp petrol engine with a minimum 28hp diesel. The other avers that a 16hp diesel will be right. Quite a gap in size and price! Cost is of course an issue, but so's safety. Here's the dilemma. Would anyone care to make observations?

Answer 1

While the 16hp is sufficient sustaining 8mph, you must consider reliability and fuel consumption. You would be overworking it and spending more money on diesel and repair in the long run. So far there are really no bad answers here except that I do favour the Yanmars. In my opinion the larger engines stated are an overkill. A balance of reliability, fuel efficiency and cost can be achieved with the 20hp and the 13" dia. prop. I know , you think I'm just another wizz bang with a calculator, but this is Yahoo Answers after all and we must give the best advice we can muster.

Answer 2

All I can do is share my experience. I owned an Ericson 30, with about the same displacement , that was originally fitted with an Alba gasoline 12 hp , with a 1:1 gear ratio , turning a 2 blade 13" screw. This may seem underpowered, but it moved nicely in all conditions at hull speed. After it died, and I upgraded to diesel, I went with a rebuilt Volvo MD2 18 HP. with an approx. 2:1 reduction gear turning a 13" 3 blade screw with heavy pitch...I could achieve hull speed at 1/2 throttle, and would only use about 1/2 gallon of fuel per hour...the engine was bullet proof and never let me down. The only drawback was the increased weight, which I was more than happy to trade off for the increased reliability and safety . I don't think Volvo makes these any more, but I'm sure there must be something comparable in their current line of small motors.

Answer 3

Any 16 - 30 hp diesel will do the trick, depending on the local current stregnth. You only need the engine for docking and motoring in and out of harbours prior to, and after setting sail. If you can get the engine to moce the boat at 5 MPH, that's all you need. Get the one that will do the job, and have the seller/installer guarantee that it will move the boat at a pre-specified speed, at 2/3 to 3/4 throttle.

Answer 4

The rule of thumb, for a boat used in normal conditions, is 1HP/WL ft. hence your 28HP suggestion, but the fact is you can put a much smaller engine in if you are not very heavy displacement, if you do not use the engine a great deal and are not sailing in locations with heavy currents or tidal streams. Another factor would be what you drive off the engine --- i.e. large alternator, refridgeration, water maker. If you have a lot of add ons look for a slightly larger engine. In other words both your consultants are right. In either case one of the small Yanmars (2 or 3 cyl.) would do the job. And, do not forget to consider weight and space available.

Answer 5

Volvo 2 cylinder diesel engine. Shaft drive to fixed 3 bladed bronze propeller.
Two 12 volt batteries, charged by engine alternator. 1 Kw inverter.

Answer 6

i was raised in the sea food industry an we have 20ft 25ft 30ft 35ft an even 40ft vessels that operate in the gulf of Mexico!! standardly in these wooden boats we have inboards with diesel powered engines!!


4,6 an v8 cyl Cummings,,,,, 4,6 an v8 cly Detroit diesels..
with gear ratio of ,,1to1,,, 2 to1,, 3 to 1 even 6 to 1,, pending on wheel size room..

these boats range speed from 20 nts to 35 nts ..

of course were talking 8, 10, & even 12000 dollars but very very realiable an strong!!!

dont know if this will help you are not with your yaht but good luck!!

Answer 7

Freedom 30's are powered by Yanmar 2 GM and are very suitable and give you plenty of space to work round the engine.

Answer 8

225

Answer 9

20 hp will do it.