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Old 29 May 2015, 15:57   #1
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Our Ideal rib....thoughts?

We we're thinking of buying/ assembling a new rib. We have narrowed it down to a Humber 6.0m or 6.3m with either a115 single on the back or two 60's. If one 60 went down would the other 60 on its own be able to get the rib to plane? The weight of two 60's is the same approx as one 115. We were keen on twin 60's.Any thoughts? What top speed could we expect. We're more interested in cruising. What speed is it likely to cruise ? Many thanks Nik
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Old 29 May 2015, 17:30   #2
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Destroyer or ocean pro?

You can probably get a lightly loaded 6m to plane with 60hp BUT the prop you would choose would be very different from if it was half of a pair. You might still be able to find a chromite that works.

If you go twins make sure the electrics and fuel systems are independent otherwise you don't really get redundancy.
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Old 29 May 2015, 18:14   #3
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Hi. What have you crossed off to arrive at your final choice? A 6/6.3m rig with 115 or 2x60hp is not gonna be too lively.

Don't dismiss 1x main and a decent sized aux. Don't forget, twins are 2x£s.
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Old 29 May 2015, 18:15   #4
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Go for an Ocean Pro, doesn't matter whether it is 6m or 6.3m.
There is not a lot of width on the transom to squeeze in two OBs and I don't believe you need twin engine redundancy with the modern engine's reliability.
I would go for a single OB, I had a Suzuki DF140 (which in reality is circa 125 hp) and it gave me a top speed of 40 kts with an "all day" cruise speed of 30 kts.
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Old 29 May 2015, 21:54   #5
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Thanks all. What is the difference between the oceon pro and the destroyer? A top of 40 and an all day of 30 would do me fine. I find passengers get fed up going much faster than constant 30knts. No chat! I didn't appreciate the need for the wider transom for the twins. Will both these hulls take twins? If I had them propped so the twins ran max efficiency, and i presume a higher pitch, would that pitch be then to course to enable the boat to plane with one 60 without resorting to a finer prop? Ta Nik
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Old 30 May 2015, 02:16   #6
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Thanks all. What is the difference between the oceon pro and the destroyer?
Both are good hull's, but quite different. If you are still unsure of that then I think Mollers question is pertinent.
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Old 30 May 2015, 04:11   #7
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A top of 40 and an all day of 30 would do me fine.
You'll be well shy of these figures with the set-ups that you've proposed. You'll need to be at, or very near max design hp to achieve 40knots max and cruising of 30.

With the twins, you're going to huge extra cost for a potentially 'never' event. Unless you're planning to head miles offshore, a decent aux will get you to port easily if you should be unlucky. As Poly said, unless the twins are truly independent, the set-up will not be fail proof.
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Old 30 May 2015, 05:06   #8
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I had a used Ocean Pro 6.0, I then ordered a brand new Ocean Pro 6.3, assuming it to be just the same as the previous one with an extra foot length. When I picked it up, externally it was the same but internally the old one had a much lower floor, mounted one chine lower, and felt much more secure as the tubes were higher in relation to the console - The new 6.3 with the high floor always felt like you were sat ontop of the boat, not in it like the old one.
I had a new Yamaha 130hp and would do 40 from memory although I had an 80mph phantom at the same time so top speed was irrelevant!
It was too big really for my needs and I ended up selling it and buying a second hand attaque, with the low floor.

Although Humber make great hulls, particularly the Ocean pro upto 6.3, the finishing and fit out leaves a lot to be desired, they use the cheapest tat for fuel systems etc and items like A frames seldom fit and are bent into place etc. I've been fitting them out for nearly twenty years and have seen all their faults and they haven't really improved. The last one I did three years ago was delivered as a supposedly finished and sea trialled boat and I spent almost a week correcting their fitout with some truly shocking faults. When I bought my Ocean pro I ordered it as a bare hull and unsecured console only.
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Old 30 May 2015, 06:28   #9
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You'll be well shy of these figures with the set-ups that you've proposed. You'll need to be at, or very near max design hp to achieve 40knots max and cruising of 30.

With the twins, you're going to huge extra cost for a potentially 'never' event. Unless you're planning to head miles offshore, a decent aux will get you to port easily if you should be unlucky. As Poly said, unless the twins are truly independent, the set-up will not be fail proof.
Clearly all engines need appropriate servicing to ensure reliability however twins inherently will be a safer option. Lots of talk about separate fuel systems ( yet I bet both individual tanks would be filled from the same potentially contaminated fuel supply...............) and electrics, however obviously twins benefit from two of everything, including gear boxes, engines , props, timing belts ( where appropriate ) - components can, will and do fail! I've run both single and twin set-ups and even taking into account the extra costs I'd personally always choose twins. Not forgetting manoeuvring with twins is a joy
It would certainly pay the OP to try both styles.
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Old 30 May 2015, 06:56   #10
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however twins inherently will be a safer option..
I agree, but depending on the OP's intended usage, twins are a lot of added expensive in terms of purchase and running costs added to reduced efficiency, for only a degree of additional safety. An aux will get you home, just not as quickly.

At purchase time, it's his money to do with as he wishes.
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Old 30 May 2015, 07:28   #11
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Twins v Aux.

I know before I post this, that it's going to be dissed, but that never stopped me before...

There's twice as much to go wrong with twins. I missed many days boating when something was "off" on one of a pair BEFORE departing. That said, each of the engines failed at sea too, one in port in Scotland and one near land in Ireland (EMM fryups). I wouldn't have chanced a return to Ireland on the single (small) twin alone and an Aux would have been perfect for the local failure.

Here's the rub - it's all in yer head. When one of your twins dies, your emergency has occurred and you've played your last hand - your happy time is over anyway. You can go home at half speed or displacement speed - but you're going home either way. A 5kt Aux will get most folks in somewhere safe in a reasonable timeframe - probably their homeport on most days. Fair enough, if you're cruising the Western Isles, twins have an appeal.

If my (single) fails I have no aux. But I have still have a hand to play - I can row the SIB a bit, I might catch a handy current or breeze and make a decent landing. I have a great anchor and lots of warp. I have multiple means of calling for help. I will quite happily take a tow (people LOVE towing in broken down boats). I will more than happily let the RNLI boost their PR stats - their stations are hungry for "lives saved"
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Old 30 May 2015, 07:59   #12
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Single/twins?

Depends on what you're doing with the RIB. Local inshore Port hopping, single every time. Offshore, fishing, safety boat then twins have an obvious advantage.

One thing you ought to be aware of is that with a twin set-up you won't have twice the performance of a single of the same hp. With a twin 60hp set-up you'll have the performance of more like a 100hp single outboard because of the extra drag and prop slip.
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Old 30 May 2015, 08:09   #13
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My dive club used to have an old Humber RH600 with twin 60 Yams. Best we ever saw was 34 knots, and no chance of it planing on one engine, second engine up or down.
My money would go on a decent main and suitable aux, but it ain't my money
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Old 30 May 2015, 08:36   #14
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Twins v Aux.



I know before I post this, that it's going to be dissed, but that never stopped me before...



There's twice as much to go wrong with twins. I missed many days boating when something was "off" on one of a pair BEFORE departing. That said, each of the engines failed at sea too, one in port in Scotland and one near land in Ireland (EMM fryups). I wouldn't have chanced a return to Ireland on the single (small) twin alone and an Aux would have been perfect for the local failure.



Here's the rub - it's all in yer head. When one of your twins dies, your emergency has occurred and you've played your last hand - your happy time is over anyway. You can go home at half speed or displacement speed - but you're going home either way. A 5kt Aux will get most folks in somewhere safe in a reasonable timeframe - probably their homeport on most days. Fair enough, if you're cruising the Western Isles, twins have an appeal.



If my (single) fails I have no aux. But I have still have a hand to play - I can row the SIB a bit, I might catch a handy current or breeze and make a decent landing. I have a great anchor and lots of warp. I have multiple means of calling for help. I will quite happily take a tow (people LOVE towing in broken down boats). I will more than happily let the RNLI boost their PR stats - their stations are hungry for "lives saved"

Pretty much my thoughts on the subject in a nutshell, a coconut shell perhaps. 😉
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Old 30 May 2015, 09:08   #15
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Pretty much my thoughts on the subject in a nutshell, a coconut shell perhaps. 😉
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Old 30 May 2015, 11:16   #16
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Destroyer hull is smooth with one fat chine, ocean pro has multi chimes. It will hop up on the plane more quickly, push more spray away from the boat and sit higher out of the water as a result, basic physics. That said, to a professional (not me) it is a bit more twitchy as there is less in the water.

We have an OP and id agree re fit out. Buy a bare hull/tubes and unfitted console, then get a decent specialist to fit the rest. We bought an ex demo from a specialist. It's been mint.

Agree with all, single not twin. Also for a 6.3 you need a bigger block than a 1.5L (90-115hp typically) the 130-175 bracket tend to be a 2.0-2.5L engine. We use a 175ho 2S 2.5L V6 optimal. They're loud, but great fun. I'd be sorely tempted to get a 6.3OP with a 140 or 175 Suzuki 4S

Careful re beam too. I've seen a 6.0 Destroyer next to a 6.3OP out of the water. The OP typically has a bigger beam, and with just 0.3m more length it was just HUGE in comparison.

A narrow beam 6.0m may be Ok with a 115hp.
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Old 30 May 2015, 11:33   #17
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Lots of talk about separate fuel systems ( yet I bet both individual tanks would be filled from the same potentially contaminated fuel supply...............
Yes but the source fuel is not necessarily the only issue (contamination growing in a tank, a failed pickup, a split tank, a sea water leak into a tank, a blocked filter, a disintegrating fuel line are all possible and so it all needs to be separate), and is not necessarily homogeneously contaminated anyway. But you are quite right, even with dual everything you might be up the creek anyway.
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Old 30 May 2015, 18:23   #18
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Thanks for all the comments.I didn't appreciate two 60's would only be the same as a 100 and not 115/120 horse performance. I get the impression it would be difficult to get one sixty ( with normal pitch prop rather than fine) to get it up on the plane. Its looking more like a single 120 and an auxillary to get us home. i's back to the pub! This has shown me how important it is to actually get out on a rib with the configuration that we're thinking of. Nik
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Old 01 June 2015, 05:46   #19
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Nothing wrong with twins on a 650 rib. Here you have twin 90 HP 2 stroke cos of the weight factor. 2 x F60 4 stoke would for sure be underpowered. We had fitted them as well but quickly replaced. The best single for performance is without doubt the Mercury 150 EFI. 630 or 650 no big difference

a quick quiz but no prizes: Can anyone recognize the mountains in the background
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Old 01 June 2015, 10:09   #20
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