outboard size for RIB

[DaveNTL]

Just looking at THESE YAMAHA SPECS and I noticed that the 9.9 and 15HP are the same engine - I assume the 9.9 is de-rated somehow?

What is the forums opinion on engine size for a 10 foot RIB? Would 9.9 provide good planing, or conversley, is the 15HP a bit big? The RIB weighs 125lbs.

I've been looking for reviews but can't find one that gives comparisons or optimum sizes apart from the RIB manufacturers 'max' of 20HP

Bottom line is - I'm not going to be able to buy a 2 stroke soon and there are a few 9.9's left at one place but a 15HP at another, but it's quite a lot more dosh.

 

[kcrane]

We use a Tohatsu 9.9 two stroke on a 2.6m Lodestar with airfloor... In theory that's lots of power on a well regarded inflatable.

In practice pootling around is fine, like you would with 2hp, but as you speed up the stern digs in and the bow rises (engine is set as far down as it will go). With one person aborad and sat far enough back to steer it is tricky to get on the plane as you begin to wonder if the bow is too high and will catch the wind.

With two people, no problem, but second person has to sit well forward to push bow down, then away you go.

With three people it doesn't plane easily at all and I haven't even tried with four onboard, tho that it pushing the loading of the tender anyway.

Engine is light for the power, easy to start, worked first pull after months of not being used and runs smoothly.

Maybe a RIB would be happier to plane?

 

[dom]

I use an 8hp 2 stroke Yamaha (fab engine) on a 3.6m inflatable (Zodiac with hard inflatable floor). The whole setup is exellent. Boat planes with up to three adults - four depending on wind and sea and of course their size!

On the negative side at 27kg the engine can be a pig to put on and take off. Were I to be engaged in extended cruising and did not need the tender to double up as a toy I would switch to a 2.5hp instead.

 

[DaveNTL]

Thanks for the replies.

I've been in a similar position to both of you. I have (at the moment) a Zodiac with a high pressure inflatable floor and had (until it got nicked a week before I came back to the boat) an 8HP Mercury.

It would plane well with 2 people. Beyond that a struggle.

I'm also pondering getting a small outboard as a spare to use with the roll-up dinghy I already have.... nice idea.. maybe a bit OTT.

The advantages though would be having a spare dinghy on the davits while you're off in the other (aparently) deters petty theft on your boat because they think you're there.

The other advantage is if it's stored forward on the boat it balances the weight out a bit. Tenuous reason maybe?

I'm thinking of splashing out on a RIB that will be in 'unusual colours', and buying two Stazo engine locks , which are supposed to be the bees knees. All of this to deter theft.... well, except the RIB would be a great toy, but only with the right engine.

So I'm still a bit iffy whether it's worth spending a couple of hundred quid more on a 15HP or if the 9.9 will be plenty. /forums/images/graemlins/confused.gif I'm tending to think that it would as 9.9 is nearly 25% more power than my old 8HP and I would have thought a RIB would plane better than a high pressure floor.

 

[boatmike]

I have a 3.1M Avon RIBLite with a 9.9 Yamaha that planes very easily with 3 people on board plus luggage at around 15 knots. Hope this helps....

 

[gandy]

What sort of rib are you getting?

We were thinking of something similar as combination of tender and plaything for trips up the river or across the Bay for a picnic. For us it'll probably depend on what turns up second-hand, but it will need to be light enough to manhandle.

 

[DaveNTL]

It helps a lot boatmike - thanks very much - I'm off out to buy one! ooo exciting!

Gandy - I'm looking at a Nautica sport 10 in navy blue with a red stripe which matches my blue Nauticat with a red stripe! posh eh? It's about £400 more than most equivalent sized RIBs but the peace of mind factor that it's not common and therefore less of a target for thieves - plus, The Boss likes the colour scheme so it's win-win.

http://www.nauticaintl.com/

 

[gandy]

Cheers, I wasn't aware of them. Probably too heavy for us, we will need something that could be carried up or down the beach between us.

 

[landlockedpirate]

Looks like a very nice tender/toy. Its about twice the weight of your old air deck. IMHO go for the bigger engine, they weigh the same and you can always use less power with a bigger engine.

Looks like a deeper V than the the air decks mentioned above, it will handle better in the chop but it will take more power to get on the plane.

Mark

 

[DaveNTL]

I couldn't get a 15HP, none left. This is the last of the 2 stroke stock before they're all 4 stroke.

The dealer confirmed that it is identical to the 15HP (the owners manual confirms it too) and they said that they thought it would be plenty for the 10 foot RIB but if I wanted 15HP they could convert it. Involves some carb jet changes and other tuning.

I'll bump the thread to report how the 9.9HP works with the Zodiac once I've run it in.

Thanks all. /forums/images/graemlins/cool.gif

 

[Andrew_Fanner]

Used to have an Avon 280 rib till it was stolen. A 10HP Mariner Magnum recorded >23knots with just me on board. It would plane happily with 3 adults if you got the weight right to climb out of the hole. 9.9 will be fine.