What outboard size for small RIB/tender

[npf1]

HI've got a 9ft RIB with a 5hp 4 stroke Honda which will just about plane with just myself aboard. Does anyone know what size engine would be required to plane with two peeps plus some gear? An 8hp two stroke weighs about the same as the 5hp four stroke - would that be enough?

Thanks

 

[ChrisE]

Sounds about right but there's loads of variables like, ahem, your and your crew's weight, amount of gear and where you place all of the weight. I'm sure you knew that already.

As a guide , we have 3.4m fastroller which planes easily two up with a reasonable amount of gear with a 8hp 2ST and just about gets on plane with two up and no gear with a 6hp 4ST.

 

[BlueSkyNick]

my 3m RIB won't plane with a 6hp 4-stroke.

I have about 1.2M trip up/down river and its a bit sluggish. It plods along OK with 3 people and gear, but that's about it. As the previous owners bought it just as a run-ashore for two of them, and stowed on davits, it was probably fine.

I would prefer to have more like 10hp to give more speed when lightly loaded and more 'torque' when fully laden.

 

[tcm]

I borrowed anotherguy's outboard to check first. Note also that Big Nick is the same size as three ornery size people so needs at least 25hp to get going. An only slightly lumpy git like me can plane ooer fast with 8hp. it depends on the boat though, and you, so check first imho.

 

[ChrisE]

Ahem, young Nick you wouldn't be contemplating breaking the speed limits in the river would you?

 

[tcm]

typical consultant

That's a very good point Chris-E, well spotted.

 

[ChrisE]

Re: typical crawler

I'll take that as a compliment, well said.

 

[BlueSkyNick]

[ QUOTE ]
Ahem, young Nick you wouldn't be contemplating breaking the speed limits in the river would you?

[/ QUOTE ] I reckon that if I exceed the speed limit by 100% I will still only be going at half the speed of the HM when he is on his way to collect a fiver from a visiting boat's skipper, 30 seconds after they have have picked up a buoy for an hour to have lunch.

 

[Twister_Ken]

Wot no HM launch! Oh how we larfed.

And Lord Montague still hasn't declared bankruptcy.

 

[BlueSkyNick]

When I enquired about the possibility of pontoons on the down stream pile moorings, I was told they are still thinking about it but "but it will be very expensive and the harbour has to be viable in its own right".

Yeah, right - pull the other one.

 

[npf1]

OK, nuff Fred Drift, I'm not a fat git nor is SWMBO, so total crew weight about 19 stones plus a few bags of shopping on a Caribe 9 rib. I don't know anyone with a 8 or 10 hp to try it out first but I have seen a nice used Yam 8 for sale - hence the question of is it sufficent?

 

[Blueboatman]

Theres ribs and ribs.
Caribe have a 'proper' bottom so that will help a bit....
Every one I have seen in the Caribbean had a 15hp cos its the same weight as a 10,this gives oodles of power to help get up on the plane,and run quieter (nice for everyone else) whereas I could only just get a (your) Caribe up solo with a 5hp,usually requiring full throttle and then stepping forward to level the boat up onto the plane.

So,that extra 3hp in your new 8hp is going to do a lot of work innit ?
I am of course referring to stinky ol simple 2strokes throughout.

 

[dom]

I have a Zodiac 360 fastroller with an 8hp Yamaha. Planes with 3 adults if you coax it up and easily with 2 plus a child. Great in flat water but very wet and bouncy if any waves

 

[BlueSkyNick]

you're right, sorry about the Fred Drift - ChrisE started it, but got punished later - won't bore with how.

But there is a serious point amongst the banter - it depends how far you need to go, and hence at what speed for how long and why do you need to plane. Just SWMBO and yourself with shopping, going a few hundred yards, is different to a long trip to a mooring like mine.

I am 19stone on my own, and 6hp will push me along OK, but not planing. The boat lived on the river during the summer so got a bit weedy underneath too. With a better weight distribution, I'd have thought 8hp on a Caribe would be fine.... but can't say for sure!

 

[npf1]

Thanks for the responses. I might go for it and ebay the Honda 5hp. And if it doesn't work eBay the 8 too!

 

[npf1]

oh .. do those doel fin things do anything or just another b****x gimmick?

 

[ChrisE]

Doel fins, again depends upon your craft and the way you use it. I had one on a fishing boat of mine and it really helped to get it on plane. Mind you I'm talknig about one ton of wood and a 40hp 2T. As I understand it all depends upon whether you can tilt your o/b to get the lift that the widget is undoubtedly capable of providing. As young tcm says, if you can find someone who has done on it on a similar rig to yours....

Fred drift be buggered, this forum desperately needs more (political statement for the day)

 

[tcm]

I think you're probly right. One- up 15 stone a zodiac with crappo inflaty keel and 8hp Yamaha would plane nicely. 15hp it would go bonkers with 25 stone on board. I wd get the biggest manageable engine - but more than about 5hp is a bit of a slog - putting it on is fine taking it off, oh flippinek...