Which RIB & engine?

[EmeraldCoastSailor]

For years I used a 2.5hp on a 10' RIB and it got me to where I needed to go. While I'd like to plane getting the motor up off the dinghy and onto the rail mount without a crane was the limiting factor for me (I don't have davits). I could get the dinghy on the foredeck for passages by myself but it took a bit of effort. As a result, I recently downsized to a HighField UL260 hypalon aluminum RIB that weighs 71lbs and I upgraded to a 3.5hp that weighs the same as a 2.5hp. Can't wait to try my new setup.

[a64pilot]

What kind of 3.5? What does it weigh?

[CarinaPDX]

My old AB 260 fiberglass dinghy with 15hp 2-stroke Mercury would (just) get 3 adults up on a plane, but not 4. It weighed in at a nominal 111 lbs. My new dinghy is a Zodiak Cadet RIB aluminum hull, which should drop the weight down to about 82 lbs. I don't expect to get 4 up on a plane with it, but just maybe...

Keeping the weight down is helpful for handling the dinghy, whether lifting aboard or bringing her up a beach, so consider getting an aluminum RIB. As far as planing goes a longer hull is better, so if you can fit a 3m or even 3.5m (10-12 feet) RIB in your davits and on deck you will be more likely to get 3 adults up on a plane. Personally I wouldn't consider anything less than 10hp for your needs, and would pick up an old 15hp 2-stroke if possible. That extra horsepower is useful for getting on a plane, and also makes the dinghy powerful enough to use for towing/pushing your sailboat in a pinch.

Greg

[tarian]

I have a heavy 3,2 rib and can easily pull it onto the front deck with the spare Halyard and small winch with the lady helping , so weight is not an issue up front , if on a boat that can take it, I do not use Davits as they would need to be substantial for the weight of the Dink , and the potential of a wave crashing over.
For a Fiberglass bottom it will be heavier than an Aluminium bottom , my Rib is minimal 10 hp to plane with 2 adults 1 child 2 dogs both over 30 kg, I had a 15 hp and it was the business , but this was to heavy to store on rails and pull up for 2 , it can be done but tiring, I would not consider anything less than 10 hp if you want to plane and get out and about exploring , rather than just using it as a water taxi#
Also look at 2 stroke versus 4 stroke,
2 stoke is lighter and can give you in some cases more power ratio than the same 4 stroke so you can down size an engine

[Bulawayo]

Interesting stuff.....but a vital factor has not been mentioned. If its for 'local' waters only then you are likely on the right track. If you are going to be doing blue water cruising then the advice to get a 15hp and a >3m RIB is totally sound. If cruising long term you will want the bigger RIB and outboard. I agree that if you are parking off at marinas all the time, then the bigger set up is not required. I am big enough to lift the 25hp Yam Enduro (always with a line tho') but our Yam Malta still saw a lot of use. Our dinghy lived on the davits but on a passage the dinghy lived forward - lifted by hand sometimes and at other times via a pole and halyard.

[IslandHopper]

Originally Posted by SY Kelpie

A RIB (i.e. hard bottom) is a given. I've heard of people getting small lightweight RIBs planing with much smaller engines than that. Most of the RIBs I've been looking at aren't rated for anything over 10hp anyway.
It would be great to hear specific real world examples of RIB/engine combos that can plane with three people aboard, using smaller engines.

3.1m alluminium rib with 15hp 4 stroke gets on the plane with my two adult brothers and myself it will not do it with the 8hp 4stroke

[EmeraldCoastSailor]

[QUOTE=a64pilot;2832547]What kind of 3.5? What does it weigh?[/QUOTE

I got a Tohatsu, which someone told me was the same as Mercury (made by same manufacturer). Both weigh 41lbs according to the specs. I realize I might not be able plane very well but another reason I got the aluminum RIB as opposed to a soft bottom was to have some ability to row a bit.

[a64pilot]

It is 41 lbs., for a long time the little Merc’s have been relabeled Tohatsu’s.
I’m searching for a small motor as a back up motor and for those times we are in anchorages that planing isn’t allowed.
Yamaha two stroke 2 HP is 22 lbs and the Suzuki 2.5 is I believe 30 lbs.
I was hoping maybe that there was a 30lb 3.5, but I don’t think there is.

[malbert73]

I’m about to get a highfield 9.5 and will likely get a new Tohatsu 15hp EFI OB which I am told will likely be more reliable.
I also have a Trinka 10 which we use when local chesapeake cruising due to rowability and sailing rig. But when we leave the Bay or do longer cruises we’ll take the RIB.

[wcrosby]

Originally Posted by SY Kelpie

We're thinking that we should upgrade to a RIB once we move aboard the boat. I've read different things about what to expect in the way of performance, and what size of engine is necessary, etc.

Ideally we would like to keep the overall cost and weight down, buying secondhand if possible. I'd love to be able to keep the engine size manageable, say a 6hp, or a 10hp as an absolute maximum. But I've been told that using an engine that is too small will result in the boat not getting up on the plane, and using more fuel as well.

So- what we need is something no more than 3m long, preferably with Hypalon tubes, and with enough performance to plane with three smallish people aboard... let's call it an all up crew weight of no more than 200kg.

What combinations of RIB and engine are going to achieve this?

I bought a Highfield Aluminum Hull RIB with Honda 8HP Engine -- less than 200 pounds overall, and a very good combination!

[Dockhead]

Originally Posted by SY Kelpie

Thanks, that's great information.
I wonder how much the design of the RIB affects the hp needed to plane- or is it really all down to weight?

We are looking into RIBs of the same sort of weight as yours, up to around 40kg plus engine. The Tohatsu 2 stroke 9.8 seems like a great engine from what I've read, at under 30kg.

My experience is the same. I had an 8hp Selva on our 310 Avon Lite folding RIB, and it would plane fairly easily with two non-obese people without heavy gear, but struggled with 3. If you think you will be planing a lot, you want as much horsepower as possible.


But you should be really clear that you need that capability, because it comes dear. If you're happy to be able to plane only one-up and not often, even 3.5hp may be enough if the RIB itself is light (their weight varies greatly), and this is much cheaper and vastly easier to handle. You can handle a motor that size with one hand and don't need tackle; by 8hp it's already a two-man job or tackle. By 15hp it's already a pretty serious operation, plus the boat is weighed down by the motor.


People cruising in the Caribbean typically go for miles and miles in their dinghies, and there are no speed limits; a small motor just wouldn't suit there. But where I sail, in Northern Europe, 99% of my dinghy use is just put-putting around anchorages or harbours over short distances in sheltered water, and in harbors and estuaries inevitably with a speed limit, and a larger motor is just superfluous. I even consider going to electric.


YMMV.

[Dockhead]

Originally Posted by EmeraldCoastSailor

I got a Tohatsu, which someone told me was the same as Mercury (made by same manufacturer). Both weigh 41lbs according to the specs. I realize I might not be able plane very well but another reason I got the aluminum RIB as opposed to a soft bottom was to have some ability to row a bit.

I have the same motor -- bought as an emergency replacement for an unexpectedly broken 8hp Selva.


This motor has a poor reputation, but in my usage -- so far, so good. It was slightly hard to start over the summer, but interestingly with age has now begun to start very well indeed. So far runs perfectly. And it is marvelously light -- I think 10kg less than the Selva it replaced.

[a64pilot]

The flip side is me being here in George Town in the Bahamas. It’s jug your own fuel and at least a mile of open water to the gas station dock, in often 15 to 20 kts or wind in open water.
There having a big motor and dinghy is golden, without both carrying two people and four 5 gl jugs of Diesel, your going to get soaking wet.
Big motor you can raise the bow high just on plane and take some pretty large waves and stay dry, it takes at least 15 HP to plane in heavy winds and seas with a load.
You want to just barely plane though, go fast and it will beat you to death.

I’m going to get me a little motor, cause as good and reliable as this fuel injected Suzuki has been, given long enough, everything breaks, and parts are nearly non existent sometimes.
I can’t row this RIB any significant distance, nor against any current or wind to amount to anything.
So I think once you give up on the idea of planing that there just isn’t much difference between a 2.5 and say a 5 hp motor, if neither will plane, but a 2.5 is sure a lot easier to throw around.

[bstreep]

Having gone the "cheap" route the first time, we are buying a new AB RIB and putting our recently acquired Yamaha 2 stroke on it. We went with a Mercury Airdeck. What a piece of junk. That was 9 years ago. It now needs its FIFTH airdeck. At $500 a pop, including shipping, we would have been a head if we'd bought an AB 9 years ago. We would now own a 9 year old AB rather than a 9 year old Mercury, for about the same price. And now, with a new floor, the Mercury is worth... about $500. While the Mercury Hypalon dinghies have a 10 year warranty (prorated), the floors are PVC, and they have just a 1 year warranty. Oh, in case you were wondering, this dinghy has been under cover 95% of the time - unless it's in use, it's covered. And it's the seams that go, and no, they can't be reglued. So, my advice is, buy a GOOD quality boat.

[SY Kelpie]

Originally Posted by Dockhead

My experience is the same. I had an 8hp Selva on our 310 Avon Lite folding RIB, and it would plane fairly easily with two non-obese people without heavy gear, but struggled with 3. If you think you will be planing a lot, you want as much horsepower as possible.


But you should be really clear that you need that capability, because it comes dear. If you're happy to be able to plane only one-up and not often, even 3.5hp may be enough if the RIB itself is light (their weight varies greatly), and this is much cheaper and vastly easier to handle. You can handle a motor that size with one hand and don't need tackle; by 8hp it's already a two-man job or tackle. By 15hp it's already a pretty serious operation, plus the boat is weighed down by the motor.


People cruising in the Caribbean typically go for miles and miles in their dinghies, and there are no speed limits; a small motor just wouldn't suit there. But where I sail, in Northern Europe, 99% of my dinghy use is just put-putting around anchorages or harbours over short distances in sheltered water, and in harbors and estuaries inevitably with a speed limit, and a larger motor is just superfluous. I even consider going to electric.


YMMV.

It's a fair point that the tender needs to suit the cruising area.
Our plan is to initially head south from the UK to Spain and possibly spend a season in the Med, but longer term the aim is to cross to the Caribbean for at least a couple of seasons.
I've heard that it can be cheaper to buy a rib/engine once we've crossed the pond, and that saves us having to cart about an oversized dinghy and engine for a few years if we don't really need it. But we'll be buying secondhand so I'm inclined to think that I'm quite likely to spot a bargain in the couple of years left before we leave. It also lets me get the boat set up to carry the tender, e.g. davits, chocks etc. I can do all that at home easier and cheaper than doing it along the way, I think.

The ideal RIB for us would be an ali hulled hypalon type, pretty small, say 2.8m, or 3m absolute max. Should be looking at 40kg, or even less. If it's not too much to ask I'd even like something that's OK to row. I have heard that some of the mini RIBs are actually quite good to row, but much of it must depend on the setup of the rowlocks and the thwart.