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Old 02 August 2004, 11:27   #1
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Auxiliary Engines, Again!

Spotted a few RIB’s and hard boats in various harbours in Minorca with some neat solutions to mounting auxiliary engines and folding ‘Bimmi tops’. Unfortunately I didn’t have my digital camera with me each time so can’t really pass them on.

Interestingly every boat had an auxiliary engine or twins on the back, they obviously do not have the emergency back up we do, so need to ensure they can look after themselves.

One sports boat of only about 6m with a Mercruiser inboard engine was very interesting, the owner opened the engine bay to show me the solution of which he was obviously very proud.
It had a Yamaha 50HP on an auxiliary bracket on the Transom, connected up to a separate steering wheel, fuel tank, and remote controls with PTT all located inside the main engine bay. The engine had an over centre type strap on it fixed down to an eye to stop it bouncing about. The owner could prop open the engine cover and drive the boat from the rear bench seat in relative comfort. A bit OTT, but a great solution for an inboard equipped boat.

Now to start a discussion.
Imagine a similar set up on a 150HP outboard equipped 6M RIB with the extra steering set up for the 50HP on the front of the transom but reversed to steer the right way.

Here are my thoughts.
With say twin 90HP’s, you get maybe the equivalent of a 150HP single but use more fuel. You’d need 2 separate fuel systems, and how often do you see a back-up steering system. If one engine goes down, the remaining engine will struggle to get a loaded boat up on the plain, so will use loads of fuel labouring the boat through the water.
You are also using both engines all the time, so both need servicing etc.

If the single 150HP goes down the 50HP will still not get you on the plain, but will it use less fuel pushing the boat through the water than the remaining 90HP above?

Also, will the 150HP single use more fuel carrying the auxiliary 50HP around all the time than the twin 90hp’s will use anyway? I think it’ll use less.

I wonder what weighs more, the 150HP plus 50HP or twin 90HP’s?

Could you counter balance the offset auxiliary 50HP by stowing enough gear and auxiliary fuel on the opposite side of the boat?

Nasher
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Old 02 August 2004, 12:15   #2
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Say what?
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Old 02 August 2004, 12:20   #3
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I think you have been sitting out in the sun for too long!
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Old 02 August 2004, 13:27   #4
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Amazing what you think about with time on your hands!

Made sence to me though, the 50Hp will get you home against the tide, unlike a 7Hp

Nasher.
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Old 02 August 2004, 14:22   #5
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But really where are you going to put a 50hp aux?
And its a lot of weight to hang on the transom in the up position, id fancy that it'd break its mountings.
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Old 02 August 2004, 14:35   #6
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Can't see the point my self; in my opinion a 50hp engine with PTT and remotes etc. is a very expensive auxiliary engine! (for a 6m RIB!) Your still going have to get it serviced etc, so is gona’ cost the same to run regardless.

And surly, in an emergency situation (assuming you have plenty of fuel) fuel consumption isn't going to be your biggest worry!

I would rather have a 150hp with a 8hp auxiliary - it's still gona’ get you home.
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Old 02 August 2004, 16:07   #7
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Aux means aux.

A full flavored imagination!

Just buy a 15hp 4stroker and it will give you a good 5 - 7 knots
Why 4 stroke?
Because this way you dont have to have an extra fueltank with mix fuel.
My 6.5 Marco cruise rib can troll all day on the little engine while trailing fishing lines.
Any smaller you are underpowered and any bigger you have weight issues.

I have my aux permanently hanging on my transom, well lashed so it doesnt flop around while I tackle rough seas.
It is only a matter of 3 minutes to unlash it, lower it and pull the rope to start it.
It makes all the difference in the world when your main has gone on strike while you are tackling rough seas close to a rocky shore...!
You will not fly out of the situation but you will certainly inch out.
Will post photos as soon as I reduce them in size for posting.
Also I will post some photos of my bimini which folds out of the way neatly and then once open it can hold itself while I run at 45mph.
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Old 02 August 2004, 17:44   #8
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Didn't say I was going to do it, just after some comments about what I had seen, and thought about whilst laying by the pool.

Remember the Minorcan boat had a lot more room as there was only a leg competing for the transom space, and if your main engine went down between Minorca and one of the other islands or mainland its a long way with a 10Hp.

Nasher.
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Old 02 August 2004, 23:02   #9
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would a 4 hp 4 stroke work as a good aux for a 4m rib?

How does a 4 hp 4 stroke work for a 4m Avon rib? All this talk of auxillary motors makes me want that extra insurance. My main is a 30 hp Suzuki 2 stroke with oil injection.
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Old 03 August 2004, 03:53   #10
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Quote:
Originally Posted by boatster
How does a 4 hp 4 stroke work for a 4m Avon rib? All this talk of auxillary motors makes me want that extra insurance. My main is a 30 hp Suzuki 2 stroke with oil injection.
Yes It should do the job!
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