Sharpie Schooner 42 with an outboard motor

The in post #42 shown video (7:15 to 8:16) + post #44 and #45 also show that 20 hp is ample power to propel the topic boat.

Increasing items the plans call for will make you end up with a boat with zero loading capacity or even less, and on top of that a big chance she'll be floating not anything near level.

If you don't trust the designer, then you fare better by not building from his plans.

 

The example diesel engine in the Parker Terrapin 42 plans is rated for 19 Hp prime power @ 1,800 rpm.

See the text¹ in the cross section. Below a quote of the main specs of the plans' example engine.

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¹ ‘‘Isuzu 3LD2* or equiv. 3 cyl.’’​

* an Isuzu Industrial Diesel Engine​

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Dry Weight (kg) 132 (291 lbs) - Note: that's without the prop + shaft + transmission + marinising the engine.

(Compared to that massive weight any outboard option certainly will save a lot of weight, though the well will cost some buoyancy, but that loss will be far less than the saved weight.)

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Gross (SAE J1995)​

Max. Rated Output (kW/min-1) 29.0 (39 hp) / 3250​

Max. Torque (N.m) 97​

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Net Performance (ISO 3046)​

Max. Rated Output (kW/min-1) 28.0 (37.5 hp) / 3250​

Max. Torque (N.m) 96​

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Min.S.F.C (@Full Load) (g/kW.h) 230​

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Generator Set Power (Net)​

1500 rpm Stand-by (kW) 13 (17.4 hp)​

1500 rpm Prime (kW) 11.4 (15.3 hp)​

1800 rpm Stand-by (kW) 16.2 (21.7 hp)​

1800 rpm Prime (kW) 14.2 (19 hp)​

 

@Angélique

Read the plan again, it is written 40hp for the Terrapin 42.

It is also possible to install in the Terrapin 42 twin outboard in a well similar to Exuma 44.

After talking to Rueul Parker he did not think that twin outboard in a well is the best option and much desirable. Rueul Parker much prefer an inboard diesel as drawn in the plan.

My option of using an outboard or a saildrive is from my own interpretation of Rueul Parker plan for the Terrapin 42. According to me a 40hp diesel saildrive would be a much better option than a 40hp outboard but at 3x the cost!

This is why I am scatching my head to find a solution for the outboard engine.

My decision is not made yet!!!

 

The in the plans given example diesel inboard is rated for a max power output of 39 Hp, and for 19 Hp prime power output, at least according to the engine's manufacturer specs as linked and quoted in post #47.

 

About your saildrive option, below some example drawings...

Terrapin 34​

Terrapin 42​

Exuma 44​

The long and shallow skeg in the Terrapin 42 plans has a hydrodynamical and a structural function, both these functions would be damaged if you interrupt or prematurely cut off the skeg for the leg of a saildrive.

The in the plans given inboard option calls for a shaft drive, so the skeg stays hydrodynamical and structural intact, with the propshaft going lengthwise through the inside of the skeg.

Parker draws the single outboard option off center, just beside the skeg, so the skeg stays intact.

And the double outboard option is drawn up on both sides of the skeg, so again the skeg stays intact.

So in all the plans' auxiliary power options the long and shallow skeg stays uninterrupted and also not being prematurely cut off intact.

How would you do that with the leg of a saildrive ?

P.S.​

In my view your post #1 single center outboard option has the same issues, the prematurely cut off skeg causes a structural problem, as well as extra hydrodynamic drag and less tracking capabilities, which needs to be compensated by the larger stern mounted rudder, and so causing even more drag...

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When messing with the underwater appendages of a boat you easily do a lot of damage to the boat's capabilities.

 

"2. The sailboat needs to be large enough for a family of 5, my wife, me and 3 kids."

Is this boat a bit small for your needs ? What about a Colvin Gazelle / Kasten Redpath sized boat ? - Mark

 

with outboard(s) you may have enough power but not enough blade area for an efficient (and safe) installation. My 'guess' is you should have about 18" dia minimum.... or the equivalent area.

 

High thrust outboard versions in the range of 50 ~ 60 Hp generally have a prop dia max in the Ø 14" ballpark, the to choose pitch varies off course upon application.

 

Kasten's Redpath is a Colvin Aderyn Mor* clone. There's a 1995 UK pro built for sale in the Netherlands, can't build for the money they're asking, and since long for sale now, so probably they're inclined to drop when there's a bid.

Tom says about her: ‘‘ the next popular size was the 41-footer, known as ADERYN MOR. She is usually built as a gaff ketch or a gaff schooner. Also noted for her passage-making ability and seaworthiness, she has quite a bit of interior room. The original was built in New Zealand by her owner; I also built one in my yard and, on trial runs, I could find no fault with her nor make any suggestions for improvement. ’’

* Wayback Machine link (to Tom's moderate displacement ocean sailing designs), since Tom's ^R.I.P. website is offline, and probably won't be ever started up again.

P.S. - Tom's Gazelle and his larger light displacement sailboat designs, as stored on the Internet Archive ---> Wayback Machine.

 

It will always be a mediocre installation. If the above is true about a 14" prop then it's not going to be efficient. Get a copy of Dave Gerr's propeller handbook before you spend more time worrying about this. Go back to your SOR that you posted and focus in on your requirements - you'll realize effort should be made to locate a good second hand engine if new costs are too high.
Mark

 

It's a light boat, only 23,000 lbs (10,433 kg) displacement.

 

What about this option?

A Torqueedo pod Cruise 10.0FP combined with a King Canada Generator 10000 watts peak combined with enough AGM batteries to give me around 45-60 minutes of running time.

Pod drive Cruise 10.0 fixed pod for motorboats / sailboats https://www.torqeedo.com/us/en-us/products/pod-drives/cruise-10.0-fp/1252-00.html

Gasoline Generator with electric start and wheel kit 10,000 watt http://www.kingcanada.com/detail/gasoline-generator-with-electric-start-and-wheel-kit-10-000-watt-KCG-10000GE/447?cid=38&mid=5

When only getting in and out of the marina I will rely on the batteries alone, when motoring for a long time the generator would be used.

Would this combination allow me to cruise at 5-6 knots for the whole day if I have enough gas? Anybody as experience with this type of set up on a sailboat?

 

Forget about this gas generator idea!!! It is just too dangerous with the Carbone monoxide! Even if it is installed in the cockpit in a case with a bilge blower to evacuate to carbon monoxide, there is a potential that the wind bring it back in the boat!

 

Millions of boats around the world use gas propulsion and they don't blow up, as hinted at above, though that generator wouldn't last long in a marine environment, a real marine generator would. This is a Really Mickey Mouse way to get a gas/electric pod to work. It's not especially efficient,with loses from both units. Just because something can work, doesn't mean it's an approuch you should consider. A real gas pod would be the ticket and with some tinkering you could slave an electric motor to run off a battery bank if you want, though you're diving into the same type of hole the gas/electric pod would. A real pod could live under a bridge deck and likely not intrude into the cabin or cockpit.