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Old 15 September 2012, 15:38   #1
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Auxy Engine

I am after an Auxy engine for my 6.5M Ocean pro.

Was thinking maybe 10HP range, but would welcome any advice on it.

I would want it to get me out of trouble, and get me back to port in case i need.

Not too worried about weight as I believe the max transom weight is 400Kg, and I have a 135 BRP Ficht on there. (i got the 400Kg max from the manufacters manual for the boat)

any idea's? 4 stroke vs 2 stroke? and size? am prepared to go for up to 15HP I would think? any other ideas?

Cheers,
Gary
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Old 15 September 2012, 18:20   #2
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Most of the 2 stroke 10hp and 15hp models are the same weight, possibly the 4 strokes too, which by the sounds of things isn't really a major factor for you (unless your removing it each time).

Without turning it into a 2 V 4 stroke debate ill add some "thinkers" for you

Your fuel supply. 2 stroke will mean carrying a spare pre-mixed tank. 4 stroke can offer the option of swapping connectors on main tank

Storage. If its remaining on the transom not so much of an issue. If you intend fitting when needed a 4 stroke will need careful consideration for storage. Plus they are heavy to hang over the transom in a swell.

Performance/economy. Depends on the distance it's likely to need to take you. If we're talking miles you'll need to be carrying. Larger spare tank for 2 stroke. 4 stroke again you can use you usual fuel (which obviously doesn't help in event of main nine failure due to fuel contamination) supply.

Purchase/Service costs. 2 strokes are not really much cheaper to buy right now. They will be cheaper to service. Re-sale value will most likely remain with the 2 stroke in the short term, 4 stroke long.

Going back to the subject of what size, I think an 8hp is your lowest consideration and 15hp your max. Anything less will struggle for a long haul, anything more is overkill.

A 6hp will give you around 5/6 knots without taking into consideration conditions. Sounds fine for a short trip back in flat calm seas but sods law tells us it'll be in a chop you need to use it.

Peter @ Boatsandoutboards4sale ~ askboatsandoutboards4sale@sky.com ~ 07930 421007
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Old 15 September 2012, 18:52   #3
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Quote:
Originally Posted by Boats&Outboards View Post
Most of the 2 stroke 10hp and 15hp models are the same weight, possibly the 4 strokes too, which by the sounds of things isn't really a major factor for you (unless your removing it each time).

Without turning it into a 2 V 4 stroke debate ill add some "thinkers" for you

Your fuel supply. 2 stroke will mean carrying a spare pre-mixed tank. 4 stroke can offer the option of swapping connectors on main tank

Storage. If its remaining on the transom not so much of an issue. If you intend fitting when needed a 4 stroke will need careful consideration for storage. Plus they are heavy to hang over the transom in a swell.

Performance/economy. Depends on the distance it's likely to need to take you. If we're talking miles you'll need to be carrying. Larger spare tank for 2 stroke. 4 stroke again you can use you usual fuel (which obviously doesn't help in event of main nine failure due to fuel contamination) supply.

Purchase/Service costs. 2 strokes are not really much cheaper to buy right now. They will be cheaper to service. Re-sale value will most likely remain with the 2 stroke in the short term, 4 stroke long.

Going back to the subject of what size, I think an 8hp is your lowest consideration and 15hp your max. Anything less will struggle for a long haul, anything more is overkill.

A 6hp will give you around 5/6 knots without taking into consideration conditions. Sounds fine for a short trip back in flat calm seas but sods law tells us it'll be in a chop you need to use it.

Peter @ Boatsandoutboards4sale ~ askboatsandoutboards4sale@sky.com ~ 07930 421007
Thanks for the reply Pete.

I have dual tanks, a 90L and a 150 underdeck, so the contamination issue is reduced, but understand what you are saying. I would probably get an external tank to keep as a seperate supply.

I will keep the Auxy permanently mounted, so weight is not an issue, and neither is shifting it.

Economy is not an issue, but i do think it essential to have a backup.

Looking at your answers, I am leaning to a 2 stroke 15HP, long shaft, but would welcome any other opinions?

Gary
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Old 16 September 2012, 04:06   #4
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Pennine Marine have a new Tohatsu 9.8hp 2-stroke, but it doesn't say if it's standard or long shaft. I think it's long shaft as its 32kg. Standard shaft should be 26kg. Details here: Pennine Marine Ltd > Tohastu 9.8.hp Outboard Engine - New

If its 15hp your after, then found this on Gumtree in Ipswich:
15 HP 2 STROKE MARINER LONG SHAFT LONGSHAFT OUTBOARD OUT BOARD BOAT ENGINE 15HP in Ipswich | Boats, Kayaks & Jet Skis for Sale | Gumtree.com

It's also on boats and outboards: Mariner Outboard Engine for sale , Mariner 15hp outboard motor 2 stroke long shaft - Boats And Outboards
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Old 16 September 2012, 05:46   #5
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Originally Posted by spartacus View Post
Pennine Marine have a new Tohatsu 9.8hp 2-stroke, but it doesn't say if it's standard or long shaft. I think it's long shaft as its 32kg. Standard shaft should be 26kg. Details here: Pennine Marine Ltd > Tohastu 9.8.hp Outboard Engine - New
For a 6.5m RIB, 15hp seems a bit OTT. As you push a hull toward planing speed, there is a "hump" that you're best not even starting to climb with an Auxie (IMO) as you won't see any meaningful increase in speed for the extra HP and gas burned.

That 9.8 Tohatsu is a nice simple motor (I WOULD say that) and the unit in Pennine has the weight listed incorrectly - none of them are that heavy! The 15" is 26kg, 20" (long) is 27kg and 25" is 28kg. That isn't a standard prop it has fitted - if it's a Hi-thrust model, all the better. The asking price is ONO, so some room to bargain there. They burn 4.5L/hour at WOT so the standard 12L tank will see you OK for quite a while. In good conditions you could throttle down a touch and extend that by at least another hour. If you are in the habit of carrying extra fuel "on deck" as a reserve for the main tank, then you can always keep a small bottle of 2 stroke handy to refuel the auxie if needed.

If you're planning to keep it mounted on the transom then you will have to find some way to secure it as the mounts would never survive the forces over time.
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Old 16 September 2012, 06:00   #6
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I presently in a similar position, looking for an auxy for a 6.5, from my research, have narrowed down search to a 5-6hp as feel this will meet my needs, ie get me away from danger/into deeper water/to a safe anchor area.
It is not intended as a passage maker.
I feel any bigger would be quite cumbersome to work with, in the limited space avail?
I have a bracket on the transom and the boat also has a auxy carriage bracket on the a frame.
Paul
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Old 16 September 2012, 06:03   #7
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Hi

I dont know about the currents where you live but my shetland 6.10 meters long and 1.5 tonne fully loaded uses a Honda 2.3 on loch lomomd and 5hp when out on the west coast and I still get 3-5mph out of it and I am guessing your rib is a fair bit lighter. Dont get me wrong this is fast walking pace, but that's all we need to get back to safety.

so as you will never get it over the hump with an aux I would go for a new tohatsu 6-8hp 4 stroke ( same as mercury / mariner but less money and same warranty) as they hold their money v well and will set you back around 930 inc vat and delivery or 600 ish 5-6 years old out of warranty.

Oh and buy a lock before some ****** steals it.

Dave
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Old 16 September 2012, 06:07   #8
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I feel any bigger would be quite cumbersome to work with, in the limited space avail?
Indeed Paul, that would generally be the case. However, the Tohatsu 9.8 2 Stroke is unusual as it is effectively the size of a 6hp. It is the same block as the 6hp and 8hp Tohatsu, not a derated 15hp like many "10"hp units. It weighs only 26/7kg and has a very compact head.

Being a 2 stroke it isn't fussy about which way up it is stored/transported.
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Old 16 September 2012, 06:08   #9
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Hi Gary

I hang a 8hp Johnson 4s off the back of Gwenn and if im honest, its a pain in the a*se....

It pushes Gwenn along at reasonable speed of between 2and 4 knots depending if im going uphill or down but the engine itself is sooooo heavy!! Its a right Jeepster to get on and off the transom and even tilting it up and down whilst it's fitted is a pain.

If it wasn't for the fact that i already had the engine i would have looked for a decent 2s saildrive or similar.

As Willk says, 15hp is prob a bit of overkill as based on the performance with my 8hp i would say 10hp should be perfect.

Oh and make sure its a long shaft too as you'l prob struggle otherwise...

BFN

Simon

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Old 16 September 2012, 06:17   #10
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Oh forgot to mention...

My Johnson is also a pain to store when its not on the transom also... As its a 4s it can only be stored/transported in a certain way otherwise the next time you flash it up you disappear in a mushroom cloud of burnt oil.... Lovely, especially if you do this in a nice quiet marina on a lovely saturday morning!!

Right enough of me banging on about my Johnson... :-)

Simon

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