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Old 21 December 2013, 03:09   #1
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Country: UK - Scotland
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Boat name: notorius
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small auxiliary engine choice ?

Hi - I'm new to ribbing and have just acquired a 5m Humber Destroyer and 60hp 4 stroke Suzuki ( long shaft) - I would like to put an auxiliary engine for security and wondered what size and shaft length would suit the boat. I will keep the boat
out in Tiree - quite exposed , and a back up engine would be good for safety . The main engine is well underweight - 105kg, the makers recommend a max transom weight of 135kg - so there's 30kg left - I also wondered if a short shaft would be good for getting off a beach ? - any advice greatly appreciated.
cheers
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Old 21 December 2013, 08:23   #2
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Normally 1hp for every foot, so anywhere from 4-5hp will be ample.

First thing is whether you want 4-stroke or 2-stroke. Advantages with both. In addition, fuel supply. If you hook up to your main fuel source, then that would be ideal.

2-stroke, light, easy maintenance, and normally bullet-proof unless its a 5hp Twatsoo!

4-stroke, quiet, cleaner, more frugal, but watch how they're stored (regards oil in sump)

Also how will it be mounted. If there's sufficient space on the transom, then that would be my preferred choice. Adjustable outboard brackets rattle like a bag of spanners.

The other main thing to consider is the robustness of the outboard when underway. The tilt pins on most outboards won't put up with the vibration, so considering tethering with a ratchet strap. You could use a stainless steel u-bolt, that's what I use straight into one of the transom knees as an anchor point.

Shaft length, you'll know your own boat and the freeboard at the transom. I chose a long shaft 4hp Mariner and it clears the water when underway.

Regards getting of a beach, still think you could use you main engine at a trimmed up angle, suppose it depends if you have a stainless steel propeller (danger of hitting the bottom) and what the sea condition is like.

Plenty threads on auxilliary outboards, for pictures, but holler if you want more details.
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Old 21 December 2013, 08:37   #3
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Agree with Spartacus. I have a 4hp YAMMIE 4st on my rib

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Old 21 December 2013, 13:06   #4
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Make: humber destroyer 5.0
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Thanks

Thanks for the posts, I used to have a small sailing boat, 23 ft, and we only had
a 4hp Yamaha on the back, it was ok - get you home - type of power.
Just the prop used to pitch out in anything other than calm conditions.
The suzuki and boat are new but I'm pretty cautious , more lobster pots and rogue bits of line etc are the issue - I 'll look for a 4/6hp longshaft with a separate tank .Cheers + thanks
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Old 21 December 2013, 15:14   #5
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Country: UK - Scotland
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Agree regards an auxilliary. I go to Lewis most summers. Losing the main engine doesn't bear thinking about and VHF isn't a reliable backup plan when you're bobbing out in the Atlantic.

Some engines to consider.

http://www.willsmarine.co.uk/store-p...rd-engine-715

Details of OB100178 - Tohatsu 6hp

http://www.seamarknunn.co.uk/download/usedob/used.pdf

Bridger Marine have a mint Suzuki 6hp long shaft.
John Bridger Marine
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Old 21 December 2013, 15:23   #6
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Quote:
Originally Posted by spartacus View Post
Normally 1hp for every foot,
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Old 21 December 2013, 16:06   #7
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Re. The shaft length remember "long" on a wee engine is shorter than "long" on a main.

Add that to the fact your main is probably in a cut-out and I can assure you a short shaft aux's prop will barely touch the water.

-> get a long shaft.
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Old 21 December 2013, 16:56   #8
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Quote:
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... better safe than sorry! Could end up with a bigger aux than the main lump!
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Old 21 December 2013, 17:00   #9
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Thanks for those replies, I hadn't thought about the cut out, the Destroyer has a 25inch transom, mine was cut for the 20 inch main engine, would an outboard bracket be best for the small engine to lower it down ?.
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Old 23 December 2013, 03:00   #10
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Originally Posted by spartacus View Post
normally bullet-proof unless its a 5hp Twatsoo! .
Shut it!
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