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Old 08 January 2015, 13:54   #11
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Country: UK - Scotland
Boat name: imposter
Make: FunYak
Length: 3m +
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Originally Posted by darklordhill View Post
Crossing in company would be great but I have no friends with boats.
you've got 18,429 of them you've just not met them yet!

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Maybe I should be looking for a decent size aux that has enough power to push me along at decent rate but at the same time be light enough not to hamper performance.
the usual rule of thumb quoted is 1HP per m of length - so 6HP for you - but if it would fit a 9.9 might make good progress on your boat (plenty of yachts your size will have sailed the channel with engines that scale).
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Old 08 January 2015, 15:07   #12
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Country: UK - England
Town: Bristol
Boat name: Red Alert
Make: Solent SR600
Length: 6m +
Engine: Mercury 125hp
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I have been looking for a small aux around a 9-10hp, but the next consideration is getting the right weight / balance with whatever main I get. I think I need to see more of other peoples setups with the same size boat.
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Old 08 January 2015, 15:19   #13
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Country: UK - England
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Make: Solent SR600
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Originally Posted by Pikey Dave View Post
Bear in mind that this is coming from a bloke with a twin engine boat (for sale) & who has a single engine boat on order:-


Twin engine, I specced this as a dive boat, the rationale being that we were diving 20+ miles off shore, deep stuff. If I put divers in the water, I wanted to be sure that I could get them out again, especially if they've been drifting a couple of hours doing deco. The boat has completely separate fuel & electrical systems for each engine, it will plane on one engine, the fuel tanks can be combined to a) run both engines from 1 tank, or b) 1 engine from both tanks. This means that the loss of 1 engine or 1 fuel tank doesn't mean you lose the corresponding engine/fuel. Similarly, the batteries can be combined to run/start/charge from any engine.
I've even gone as far as having separate plotters/gps so that failure of one unit doesn't mean the loss of the whole system, paranoid moi???


New boat:- Single engine, smaller boat. I've stopped diving & now don't need anywhere the level of redundancy. We still do the distances, but usually in company. We are well equipped with drysuits/plb/290N lifejackets yada yada! If it all goes brown, the worst that happens is we drift/anchor & wait for the cavalry.


Twins are undoubtedly more expensive to buy/own/keep. In your case twin 40s will nowhere perform as well as a single 75 of similar pedigree. Unless you have under deck tanks, you will have fuel cans all over the place gobbling up valuable deck space.


At the end of the day, it's your call. You did ask



I guess that the twins you have are big as only one has enough power to get the boat planing.

I think that the with the small twin 40s I was contemplating one would not get the boat planing if the other went down, so a decent aux may do just as well.

I may just steer toward the single 2 stroke 75 with an aux or I may put it off for while and save to get the super light 4 stroke yam f70 that I keep reading about, Just can't seem to find any cheap used ones.
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Old 08 January 2015, 15:30   #14
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The weight of two 40s is significant, with the 100+ litres of fuel you'll need to feed them, will it push the weight of the boat/trailer over 750KG...braked trailer needed? Probably less than 1 kn/ltr...range issues?
If you're buying second hand then you're money is better spent on one good 75hp rather than two more "iffy" 40hps. Then again if you don't spend the money wisely on engines your wife will probably waste it on something stupid like a new kitchen or shoes.......
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Old 08 January 2015, 16:01   #15
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Country: UK - England
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Then again if you don't spend the money wisely on engines your wife will probably waste it on something stupid like a new kitchen or shoes.......
Ah you no her indoors then, She has just had a new kitchen before Christmas and funnily enough new boots for christmas.

I think if I make a start on the extension she will be pleased with me and I could secretly syphon of enough for a new outboard
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Old 08 January 2015, 16:32   #16
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Country: UK - Scotland
Town: Aberdeenshire
Boat name: Sula
Make: Ribcraft 4.8m
Length: 4m +
Engine: Tohatsu 60hp + aux
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I may just steer toward the single 2 stroke 75 with an aux or I may put it off for while and save to get the super light 4 stroke yam f70 that I keep reading about, Just can't seem to find any cheap used ones.
The F70 is a fantastic engine, but if you're looking for one second-hand you'd be better off digging out a Damart catalogue and ordering your pipe and slippers now.

Its only been on the market since 2010, so I seriously doubt there's sufficent volume in the market for them to start appearing quite yet. I looked for a set of second hand Yammie 50G carbs for 2 years before giving up the hunt.

Second-hand Yammie 75hp here: Buy Used Outboards yamaha 75hp 2007 model 2 stroke, power trim, 250hrs from new 75.0HP Outboard at Bill Higham Marine
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Old 08 January 2015, 16:53   #17
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Country: UK - England
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Boat name: Red Alert
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Engine: Mercury 125hp
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I looked for a set of second hand Yammie 50G carbs for 2 years before giving up the hunt. [/url]
I did the same with carbs for a honda 90, A set turned up within weeks of selling the engine. Never say never.

That Yammie looks good, I did not know they were making them in 2007.
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Old 08 January 2015, 17:26   #18
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Country: UK - Scotland
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Make: Ribcraft 4.8m
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Engine: Tohatsu 60hp + aux
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Looks like ex-RNLI. Decals on the leg, capsize solenoid on engine tray, etc.
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Old 09 January 2015, 07:13   #19
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Length: 6m +
Engine: Twin evinrude 90 ete
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You know i always believe in redundancy and specifically purchased a RIB (nautica 680) with twin outboards. I do cross Lake Ontario quite often in the summer and the added safety it provides is a comfort level i could not do without. Having said that i never had a failure on either engine ever and the key lies in proper maintenance of the equipment.
Regardless of what you decide, keep in mind that the performance with twin 40 in your case will be nowhere near the performance of a single 75. I believe you need twin 50 to get similar performance the single 75 will provide.
As your rib is a 550 a small aux engine of around 10 hp would give you the comfort level and when you maintain the 75 properly, you probably never have to use the 10 hp
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