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Old 01-06-2015, 06:49   #16
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Re: Inboard engine, hp.

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Old 01-06-2015, 07:15   #17
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Re: inbord engine, hp.

Quote:
Originally Posted by cpt_757 View Post
The boat's displacement is very light side, about 6100lbs.
So,its about 3 tons, how about 3 hp per ton, 9hp to 10hp?
This is about the same (light ship) as our boat. We are a shallow body, double-ended canoe, with full keel and some cruising kit (dodger, dinghy on the deck, mast steps, etc).

We have a 13 hp engine that is an overkill in the marina in/out scenario; but I did imagine an extra 3 or 4 hp when entering an atoll lagoon on the ebb side.

If your target is to sail a lot and use the engine as an auxiliary only, you will find 9 do 13 hp engines to chose from. You may look up something like a Kiwiprop too, if you want to sail faster / further / better.

If your target is to use the engine to push thru head winds and currents, or if you do use the engine a large portion of your time on the water, you may look towards one notch higher a shelf - things like Beta 16, etc.

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Old 02-06-2015, 03:28   #18
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Re: Inboard engine, hp.

HP is only one aspect, another thing to consider (IMO) is the number of cylinders. Most (all?) small engines say less than 12HP are single cylinders while the 15+ HP models are twins or bigger. Rule of thumb seems to be 10HP per cylinder.

More cylinders = less vibration.
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Old 02-06-2015, 10:35   #19
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Re: Inboard engine, hp.

A close family member had a Cal 29 (4 tons+/-) with a single cylinder, 10hp Bukh diesel. And it was more than enough to take the boat all over the Great Lakes. Even through stiff headwinds, & the notorious, (stiff) square waves that are common on said bodies of water.
Regardless of whether she was empty, or had a ton+ of crew & gear aboard. Of course, there are no Tides & Currents, such as in the Bay of Fundy, to deal with either. Given the locale.

Some factors to consider which relate directly, are;
- Propeller size, & type. A high efficiency prop, with the size & pitch matched up properly with the engine & boat's characteristics (in terms of power requirements) make a HUGE difference.
- Drag of the boat; both under water, & air drag, are major factors. For example, the cited Cal 29 didn't have; a dodger, a furler, a bimini, solar panels, etc. And was, by design, fin keeled & equipped with a spade rudder.
- Tides, Currents, & Winds, common in your operating area(s).


And regardless of your choice, a few good "tools" to help the engine are;
- A feathering, adjustable pitch propeller
- A line cutter on the shaft/prop
- A stout prop shaft bracket
- Good fuel filters (multiple), & a vacuum gauge. Along with a system to easily switch between 2+ fuel tanks, if your wallet can swing it.
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Old 02-06-2015, 10:45   #20
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Re: Inboard engine, hp.

Quote:
Originally Posted by UNCIVILIZED View Post
A close family member had a Cal 29 (4 tons+/-) with a single cylinder, 10hp Bukh diesel. And it was more than enough to take the boat all over the Great Lakes. Even through stiff headwinds, & the notorious, (stiff) square waves that are common on said bodies of water.
Regardless of whether she was empty, or had a ton+ of crew & gear aboard. Of course, there are no Tides & Currents, such as in the Bay of Fundy, to deal with either. Given the locale.

Some factors to consider which relate directly, are;
- Propeller size, & type. A high efficiency prop, with the size & pitch matched up properly with the engine & boat's characteristics (in terms of power requirements) make a HUGE difference.
- Drag of the boat; both under water, & air drag, are major factors. For example, the cited Cal 29 didn't have; a dodger, a furler, a bimini, solar panels, etc. And was, by design, fin keeled & equipped with a spade rudder.
- Tides, Currents, & Winds, common in your operating area(s).


And regardless of your choice, a few good "tools" to help the engine are;
- A feathering, adjustable pitch propeller
- A line cutter on the shaft/prop
- A stout prop shaft bracket
- Good fuel filters (multiple), & a vacuum gauge. Along with a system to easily switch between 2+ fuel tanks, if your wallet can swing it.
Thank you so much for the input!
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Old 02-06-2015, 11:24   #21
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Re: Inboard engine, hp.

Were 28hp @ 3000 rpm with a 2:1 reduction spinning a 16X10 prop on a 16,000 lb full keel 32' ketch. I've never needed any more power than this.


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