out board motor well size?

I'm currently in the final design stage of of a 20 foot camp cruiser. based loosely on "Flight "an old design from the 40's
http://members.aol.com/_ht_a/polysail/HTML/flight2.jpg
I drew it to have an outboard off of the transom (as shown in the orginal plan) but I'm now considering having the motor in a well just forward of the transom with a cover. I intend to use a 10hp Honda 4cycle.
My question is how big do I need to make the well? I have the specs for the motor but my concern is, How much space do I need to leave around the motor for adaquiet airflow?
Thanks in advance for any help

Rick

 

Very nice project. Hope to see some pictures as you're building it as it should be a beautiful boat.

As to your question, I don't really know the answer, but I'm interested. Are you thinking of totally conceal the engine with a false transom a couple feet forward of the external transom for both noise and aesthetics? If this is the case, would you ever need to raise the outboard? How far down would the external transom go? And how would it be ventilated, both supplying air for combustion and venting any exhaust/fumes? I would assume the clearance for steering and ~6" above would be plenty for airflow inside the well, but I'm not sure how the air is getting into the well itself. Or are you just thinking of enclosing the forward sides and top while still leaving the transom open? Possibly with the transom simply brought forward in the center, which would seem much more practical and less troublesome?

 

Hello Rick,

Surely a nice boat you are about to build.

I would not worry too much about the size of the well as long your engine can be placed in it and you can manoeuvre it. I presume your 10 hp outboard engine is cooled by seawater and therefore the only air needed is for the combustion. So as long as you make sure that your well is not completely tight (drill some air holes) I would have no considerations.

One thing that I would be worried about is what would happen if you run aground with your engine in a well. I am not sure but as I can se from the plans your outboard will be completely unprotected and with no possibility to tilt. So if you are to place your outboard in a well I would suggest that you place some kind of keel to protect the leg and propeller of the engine.

Good luck with your project,
Morten