Inboard engine, hp.

[Tailwheel]

My



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[barnakiel]

Originally Posted by cpt_757

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.

b.

[Wotname]

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.

[UNCIVILIZED]

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.

[cpt_757]

Originally Posted by UNCIVILIZED

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!

[Sailmonkey]

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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