adding outboard to cat

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Shaun Van Poecke - 22 Dec 2007 06:31 GMT

Hi all,
I have a 16' cobra cat that i would like to add an outboard to. This is the
same as a mosquito. The outboard itself is a honda BF2D, two horsepower 4
stroke. We mainly sail on a lake, and the outboard would be handy to get
back when our finnicky winds die out, but the real reason for adding it is
because of an upcoming holiday to the whitsundays. I will need an outboard
for both convenience and safety.

I've had a look at various ways of mounting it to the back of the cat,
possibly in the same way as it is on a caper cat. I had a caper cat last
year and had a lot of trouble with this arrangement though; hanging off the
back there, it gets pretty wet and is hard to manage. It is nice being able
to steer and fiddle with the outboard at the same time though.

I had considered briefly mounting it off to one side, or even right off the
side of the cat. Would this work? It has a lot of downsides though, will
unballance the boat etc... What I really want to do is et it away from the
stern.... It's always going to be in the way of the traveller/mainsheet
arrangement and causes problems with the rudder setup.

One thing I had considered was adding it to the center of the boat. I would
make a hole in the tramp just behind the mast, just large to fit the prop
through. I would fabricate a bracket of sorts that would allow me to
raise/lower the outboard at will. There are many benefits to having it
here; it is in the center of the boat where it will disturb ballance least,
I can work on it easily if need be, earier to add gas etc... This outboard
has no reverse gear, it spins 360 degrees. It is possible to have it facing
forwards and locked in this direction, with the controls facing backwards.
One downside to this setup is there will be no allowance for 'kickback'
should I strike something. I'm not too concerned about steerage from the
outboard, or about reverse, but will I get as good of a 'drive' with the
outboard here as if it were stern mounted?

Any other suggestions? I have aluminum and wood fabrication available, as
well as good access to machining services.

Thanks,
Shaun

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Ystay - 22 Dec 2007 09:30 GMT

> Hi all,
> I have a 16' cobra cat that i would like to add an outboard to. This is
[quoted text clipped - 34 lines]
> Thanks,
> Shaun

Hi Shaun,
I have had an outboard mounted amidships on my Hobie cat. It powered the
boat fine and the balance was good too. I used a 3.3 outboard (tohatsu) and
could cruise all day on 5 bucks of gas - back when 5 bucks could still get
you gas. You might like to consider mounting it infront of the mast and
have a swivelling bracket such that the motor is stowed horizontally and
athwartships. Apart from that, there are not many critical issues with
off-sided mounting.

Arnold

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cavelamb himself - 22 Dec 2007 10:14 GMT

>>Hi all,
>>I have a 16' cobra cat that i would like to add an outboard to. This is
[quoted text clipped - 45 lines]
>
> Arnold

My boat is a monohull - designed for a small outboard to begin with.
But teh mount is a two-bar spring loaded swing up affair bolted on the
transom. I added a link that locks the engine in yaw. You can't steer
with the engine with the link in place. So it acts more like an inboard
engine - steer with rudder and pay attention to which way you are turning.

Hanging a swing up mount on a cat will be -uhm- interesting (yeah,
interesting - that's the word!).
You might hang it off the back spreader tube, but how to brace that for
the thrust and vibration?

Four stroke engines have an oil sump - so swinging it up sideways may be
a problem. Oil leaking in the water will get you more attention than
you may want. And the slick points straight at the offender.

I wonder if that little light weight cat would move well with a trolling
motor? Sure would be easier to install.

Richard

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Shaun Van Poecke - 22 Dec 2007 10:57 GMT

> Hanging a swing up mount on a cat will be -uhm- interesting (yeah,
> interesting - that's the word!).
[quoted text clipped - 9 lines]
>
> Richard

Hi Richard,
i was thinking more a 'lift up mount' than a swing up mount. While that may
sound funny, the basic idea I guess would be some kind of track up the mast,
maybe even with a block to help lift it. It would drop down onto some kind
of mount at the base of the mast. You are right about the oil... There are
only two positions that it can be stored in without leaking oil everywhere.

I had thought about the trolling motor last year, but gave it up to get a
new outboard. While the many advantages of the trolling motor are nice (no
sound, no smoke, no 'starting problems' etc) they are outweighed by the lack
of available fuel. Also, storing batteries isnt the easiest thing on a
beach cat ;-)

I made up a bracket this afternoon mounted off the stern amidships. Like
most of my projects, it was done to a deadline, not a standard ;-) I made
it up out of some old decking, some caulk, and some screws. Galvanised
bolts to attach to frame. Total cost; about $4 plus 30 minutes work. Will
let you know if it goes any good.

Shaun

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Shaun Van Poecke - 24 Dec 2007 02:56 GMT

I went out today to try out the new outboard mount I had made up....

It went ok, scooted along at maybe 5 knots. I'll take out the GPS next time
to see how quick it goes, but lets just say Im not breaking any records ;-)
I think I made it too low to the water, the prop was way down in there. Im
going to try adding an inch or two in height to the bracket and see what
difference it makes. The first run out, I had the outbaord fixed in place
and was steering by the tiller. The second run out I took off the rudders
and went with just the outboard. Even without the daggerboards down it
tracked just fine and steered easily.

The real problem was as i suspected.... The boat was far too heavy in the
rear. With only me on it, the stern was almost buried (ok, I weigh 240
pounds) with me sowewhere in the center of the baot and my partner up well
before the mast it sat ok. In the opposite situation (she's about half my
weight) it actually rode pretty good. I'm hoping that with some gear stowed
forward while on holidays this would ballance out, but probably not by
anywhere as neasr as much as I would like....

Having the outboard forward of the mast or mounted just behind the mast
still sounds appealing to me, though I'm sure it comes with its own
problems. Will let you all know how things go.

I can take pictures of the mount/motor for anyone interested

Shaun

>> Hanging a swing up mount on a cat will be -uhm- interesting (yeah,
>> interesting - that's the word!).
[quoted text clipped - 31 lines]
>
> Shaun

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Boat Forum / Building / December 2007

adding outboard to cat