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Old 07-01-2014, 00:12   #1
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Outboards on 35' Catamaran

I have recently purchased a Rogers Reef 10.5 Cat that has two 9.9HP Yamaha's mounted behind bridge deck between approx 900mm from hull ends. This is a A modification from the centrally mounted motor as per the boats design.
Whilst good for berthing (and back up) they are not happy in anything resembling choppy seas when motoring in that they cause a lot of water to spray vertically because of bracket design. I want to improve and streamline the bracket/mounting system. This would involve lifting them approx 200mm and moving forward about 200mm.

Does anybody have any experience with outboards on sailing catamarans more specifically ideal depths motor should sit in water?
And would motor hydrofoils help with motors picking up air in rough conditions

See photo attached

Thanks
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Old 07-01-2014, 00:50   #2
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Re: Outboards on 35' Catamaran

Forward is good, lifting is bad.
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Old 07-01-2014, 01:27   #3
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Re: Outboards on 35' Catamaran

Further forward would be much better. Seawind have the motors basically mounted in the cockpit, with the covers used as seating.

This is an installation I'm currently doing, which is very similar to my own setup:

These motors are about 3 metres forward of the transoms.

I've recessed the powerhead into the sheer panel, it's tucked in behind the chamfer panel. The propeller is well below the hull level. As you can see, when tilted up, the powerhead is above the bridgedeck:

From the front, pretty much completely tucked in:
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Old 07-01-2014, 04:35   #4
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Re: Outboards on 35' Catamaran

This might sound silly at first, but it may be cheaper to simply put a 20 hp back in the original nacelle if it still exists.
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Old 07-01-2014, 04:41   #5
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Re: Outboards on 35' Catamaran

Doesnt need a 20. 9.9 Yammie will do fine. But yes if the nacelle is still there, then putting a steerable centre mounted outboard would a good answer.
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Old 07-01-2014, 10:22   #6
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Re: Outboards on 35' Catamaran

You might look at the older outboard powered gemini's for ideas. Manuverability wit a single center mounted steerable outboard is quite good. I would suggest around 25hp. A 9.9 yammie may do fine on calm windless days but if you need to power into a strong head wind or current, a little extra oompf is good to have. The biggest issue is getting a 25" shaft at that horse power (after market extensions are available).

One issue to consider is the wake patterns at different speeds. I'm not sure on this boat but on the Gemini once you get going the wakes meet right at the motor which leaves the prop nicely submerged. If you moved to twin outboards next to the hulls, you would likely need probably another 5-6 inches of depth but that's not good if you have following waves trying to dunk the motor.
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Old 08-01-2014, 04:28   #7
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Re: Outboards on 35' Catamaran

Thanks for the input.
This boat originally had a centrally mounted motor I assume it was steerable in "nacelle"
which is still as it was. (used to store dingy motor) I like the installation being done by 44' cruising cat but don't have much room on this boat to move them much further forward without some serious modifications. Doesn't have a chamfer panel.
I have thought of putting single motor back. Wake pattern will keep motor well submerged. At the moment present setup is usable but not ideal. My main concern is motors being swamped which is made worse by bracket design and by the sound of it wave/wake action through hulls.
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Old 08-01-2014, 05:03   #8
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Re: Outboards on 35' Catamaran

BTW wavejumper, thats a photo of the boat of WMYC Marina slipway? Are you still there? As in still in a berth there, if so, have a look at MORE TIME OFF on F row. his system works very well.
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Old 08-01-2014, 06:05   #9
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Re: Outboards on 35' Catamaran

Quote:
Originally Posted by 44'cruisingcat View Post
Further forward would be much better. Seawind have the motors basically mounted in the cockpit, with the covers used as seating.

This is an installation I'm currently doing, which is very similar to my own setup:

These motors are about 3 metres forward of the transoms.

I've recessed the powerhead into the sheer panel, it's tucked in behind the chamfer panel. The propeller is well below the hull level. As you can see, when tilted up, the powerhead is above the bridgedeck:

From the front, pretty much completely tucked in:
Very nice upgrade.
Where were your engines before?
Will you have to seal the cover so water does not spash on the floor around the helm?
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Old 08-01-2014, 13:35   #10
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Re: Outboards on 35' Catamaran

It's not my boat, it's a boat I've been repairing since it was wrecked in a cyclone.

When it was wrecked it had a single 60hp outboard centrally mounted. Prior to that it had Torqueedo electric outboards, but they proved unreliable. IIRC 5 failed in 6 months, eventually the money was refunded. And before that it had E-Pod electric drives, which were so bad the owner removed them and threw them in the garbage.

We'll probably put a foam tape seal around the engine covers. The helm position was obviously decided based on the electric drives, which retracted up under the bridgedeck, so the outboard motor covers compromise them somewhat. In reality though, these helms don't get used most of the time, there being a third internal helm station. The outside helms are mostly only used for racing and in marinas.

My engine install is similar, but the steering wheels are further forward, in the cockpit.

There's a thread on the repair job here: Recovering From TC Oswald.
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Old 08-01-2014, 14:19   #11
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Re: Outboards on 35' Catamaran

I agree totally with the suggestion that outoboards can work very well, but that they should be mounted much further forward in order to avoid cavitation. The PDQ 32 and 36 were also available with outboards - when so equipped they had compartments in the cockpit under the cockpit seats and a block and tackle so that they could be pulled out of the water when sailing. Depending upon the seating arrangement in the cockpit and what is under the seats (i.e., storage, as opposed to a berth), it might be possible to make the same arrangement on this boat. It would require cutting holes in the bridgedeck and not the hulls.

Brad
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Old 08-01-2014, 16:08   #12
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Re: Outboards on 35' Catamaran

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Originally Posted by 44'cruisingcat View Post
It's not my boat, it's a boat I've been repairing since it was wrecked in a cyclone.

When it was wrecked it had a single 60hp outboard centrally mounted. Prior to that it had Torqueedo electric outboards, but they proved unreliable. IIRC 5 failed in 6 months, eventually the money was refunded. And before that it had E-Pod electric drives, which were so bad the owner removed them and threw them in the garbage.

We'll probably put a foam tape seal around the engine covers. The helm position was obviously decided based on the electric drives, which retracted up under the bridgedeck, so the outboard motor covers compromise them somewhat. In reality though, these helms don't get used most of the time, there being a third internal helm station. The outside helms are mostly only used for racing and in marinas.

My engine install is similar, but the steering wheels are further forward, in the cockpit.

There's a thread on the repair job here: Recovering From TC Oswald.
WOW, I remember reading an article on "Schools Out" when she had the Torqueedo electric outboards on her. That was a very nice boat. Looks like you guys are going to bring her back to life.
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Old 08-01-2014, 19:44   #13
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Re: Outboards on 35' Catamaran

LOL! Amazing what comes up on the internet. I'm in that photo. Bryan, the owner, is under the wind gen, I'm sitting on the rear beam near the lifering, Bryan's wife Rowena is in the cockpit, and Bob Oram is driving.

They had a Suzuki 15 (their dinghy motor) mounted on a transom because the original E-Pods had proven unreliable. This was one of the early runs on the Torqueedos. The photo was taken by the guys from Torqueedo.

We used that same temporary outboard setup to move the boat down the river from Monty's marina, to where we could transport her by road to the shed she's now in.
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Old 08-01-2014, 20:11   #14
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Re: Outboards on 35' Catamaran

Quote:
Originally Posted by 44'cruisingcat View Post
Further forward would be much better. Seawind have the motors basically mounted in the cockpit, with the covers used as seating.

This is an installation I'm currently doing, which is very similar to my own setup:

These motors are about 3 metres forward of the transoms.

I've recessed the powerhead into the sheer panel, it's tucked in behind the chamfer panel. The propeller is well below the hull level. As you can see, when tilted up, the powerhead is above the bridgedeck:

From the front, pretty much completely tucked in:
Has to be state of the art for mounting outboards on a cat. And a 44ft vessel also.
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Old 08-01-2014, 20:20   #15
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Re: Outboards on 35' Catamaran

Really like the outboard set up 44c. Would it be feasible to make those outboard covers into a helm seat as well?
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