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Old 23 September 2011, 20:56   #31
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Originally Posted by BogMonster View Post
I have tried it (thinking the same thing). Last time I was out I had a good run around on the aux to burn up the six month old fuel, and during that I wondered if it would help the speed if I pulled the main engine up. Main up or main down made very little difference to the speed - maybe a quarter of a knot tops. You can compromise and tilt the main up so there is just the skeg trailing in the water, and you still have most of the useful steering input but a bit less drag.

I think aerodynamics say that wind resistance increases as the square of speed (which is why you need a lot more power to get a bit more speed), so if hydrodynamics are the same, that would explain it.

You can also spin the boat on the spot by using the aux full ahead and the main slightly astern, yes it was a nice day and no I had nothing better to do than pretend I had real twins
How are you mounting your Aux Steve?
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Old 23 September 2011, 21:07   #32
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How are you mounting your Aux Steve?
I asked for my boat to be built with no rear lip on the transom, so mine is fitted straight onto the transom. I had to mod the engine mount to make it fit as the Vipermax transom is just too thick to slide the Merchatsu saddle over. After a bit of head scratching what I did was to carefully cut off the two round cupped washers on the clamps and replace them with flat washers which locate onto the stepped ends of the clamp screws, this just allows space to slide the saddle over the transom. I could have either altered the transom or the saddle but didn't want to do either, so this seemed like the best idea. It's a fiddle to mount the engine as you have to slide it on and then slide the washers in afterwards, but as I leave it on the transom all the time this doesn't really matter.

Only photo I have with the aux in is attached, but can get closeups tomorrow if you are interested.
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Old 23 September 2011, 21:28   #33
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Yes, the lip is a problem

So you run it with the Aux on the transom and tilted then? I thought about this but was concerned about damaging the Aux bracket when wave hopping. I was thinking of a stainless bracket that slide up and down, keeping the outboard in the vertical position.
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Old 23 September 2011, 21:43   #34
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Yep just as shown there. No problems yet - weight distribution is pretty even when tilted so it doesn't seem to bounce.
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Old 24 September 2011, 01:50   #35
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Interesting thread as I have just gone through all this ! (after 1st break down ever! )
Went last week to buy an aux and really liked the honda air cooled 2 HP 4 strokes at only 27lbs ! Easy to stow anywhere and just throw onto the transom when needed.
However not going to make much headway against any wind or tide.(not that we get much here)
But went for a nearly new mercury 4hp long shaft, 4 stroke instead .
But at 45lbs, hate to keep it permanantly on the transom.
So made a bracket on the front of the two pod seats ,right behind the helm.
Keeps it upright and out of the way and puts the weight forward.
When needed, I drop it on the back and as others said,lock it and use the main for steering. Not very responsive, but gets you there safely!
Gave me about 4.5 knots wide open. Not great, but hopefully avoid the ambarrasment of calling for help to my buddies on HMS Surprise; as I did last week ( Here she is dropping by with some oil ! )
Can't imagine keeping an aux on the back all the time .Seemed to bounce around everytime I went airborne, even when locked
cheers Dal
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Old 24 September 2011, 05:01   #36
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If you're concerned about the 3.3 being underpowered, what about a second hand 5hp 2-stroke instead?
Speak of the devil!
yamaha 5hp 2 stroke Outboard Engines for Sale at findafishingboat - FAFB
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Old 24 September 2011, 05:13   #37
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Originally Posted by Hightower View Post
Yes, the lip is a problem

So you run it with the Aux on the transom and tilted then? I thought about this but was concerned about damaging the Aux bracket when wave hopping. I was thinking of a stainless bracket that slide up and down, keeping the outboard in the vertical position.
http://www.rib.net/forum/attachment....4&d=1188600854

Andy, I had this set up on my old Viper 5.25... Never had a problem with the bracket despite plenty of days out wave jumping...

I used a little ratchet strap from the leg down to the bar across the bottom of the saddle to hold the engine down tight on the bracket so it could not flip up...

With regards to the lip, I spoke to Mike at Witton Glass Fibre and he said it was fine to just cut away flush to the top of the main transom as there is no wood in it so I used an angle grinder with a stone cutting disk fitted and it was absolutely fine.
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Old 24 September 2011, 05:40   #38
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I had the same problem with an auxilliary on my last boat (Zodiac Pro). It couldn't be fitted directly on the transom as the Pro had a lipped edge nearest the tubes. In the end I fitted a Plastimo stainless-steel bracket. It needed a little adjustment (cut one corner off of the fixing bracket) in order to move it as far to port as possible. Might be an issue with a heavier auxilliary, but I was fitting a 3.5hp Twatsoo 2-stroke. The Kate Moss of 2-strokes. Smokes a little but squeezes in anywhere! Only 13.5kg in weight.

The only drawback with that set-up was the bracket used to rattle like a toolbox. Underway, the auxilliary engine could be tilted up and then secured with a ratchet strap to the back of the bench seat. It was practical enough.

Last year I bought a new RIBcraft 4.8m... then wish I'd kept the Twatsoo, which I'd sold a few months earlier with the Pro.

Luckily the new boat has a relatively wide transom, has a 60hp tweaked to 70hp Twatsoo 2-stroke main engine, and space either side. I opted to go for a light-pole rather than an A-frame, more because of storage issues rather than practicality.

I wanted another 2-stroke auxilliary so opted this time for a Mariner 4hp. Completely stripped it down, new impeller, cleaned fuel tank, carb, fuel pump, renewed starter rope, spark, etc. Runs like a dream. Although heavier, it was mounted straight on the transom. There's a towing eye on the transom, but the outboard bracket fitted over the top. The steering cable for the main engine is tight next to the auxilliary, but works fine. I knew I'd have the same problem with a rattling auxilliary, so I fitted a stainless-steel U bolt on one of the transom legs, to secure it with a ratchet strap. This is essential in my opinion.

Hopefully these pictures illustrate a few options. Basically, there's always a way to fit an auxilliary engine. It might not be pretty or practical in every scenario, but the knowledge that you have a back-up engine is what it's all about.
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Old 24 September 2011, 05:48   #39
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Quote:
Originally Posted by Chris View Post
http://www.rib.net/forum/attachment....4&d=1188600854

Andy, I had this set up on my old Viper 5.25... Never had a problem with the bracket despite plenty of days out wave jumping...

I used a little ratchet strap from the leg down to the bar across the bottom of the saddle to hold the engine down tight on the bracket so it could not flip up...

With regards to the lip, I spoke to Mike at Witton Glass Fibre and he said it was fine to just cut away flush to the top of the main transom as there is no wood in it so I used an angle grinder with a stone cutting disk fitted and it was absolutely fine.
Thanks for the info Chris. I'll bear it in mind whilst deciding/designing the mounting system
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Old 24 September 2011, 06:50   #40
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Quote:
Originally Posted by limeydal View Post
Went last week to buy an aux and really liked the honda air cooled 2 HP 4 strokes at only 27lbs ! Easy to stow anywhere and just throw onto the transom when needed.
However not going to make much headway against any wind or tide.(not that we get much here)
I read somewhere a while ago - forget where - that the small aircooled engines are no use as an aux because they overheat slugging away pushing a big load. No idea if true or if it is a major problem but worth checking?

The Merc tilt support is not very strong - I used to use a small ratchet strap to tension it against the bracket but it is quite bendy and after a while I didn't bother with it.

Kate Moss of 2 strokes
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