Planing Dinghy: Hp vs Dinghy type vs #Passengers

[culebra]

I have a Highfield Classic 340 (154 lbs) with a Yamaha 2-stroke 15 HP that planes easily with 2-3 people. 4 large adults, especially with load/groceries on boat, is less likely to plane. Adding a Davis Doel fin ($33-40 on Amazon or Ebay) made planning with 1-2 people much much easier so a great addition. Have also used a 105 lb Yamaha 25 HP 2-stroke on the same boat and with 3 people it is scary fast (my kids wanted me to slow down!) so can easily plane with 4 people.

[colinalleck]

Archilles 2.1m with inflatable floor Tohatsu 3.5hp slow and steady with 2 or 4 pob

Can just plan if solo and prepared to lay prone on the floor

Cheers Col

What are you doing to do with the results as I’m looking to upgrade. Also would like those with portables boats to input as considering one

[Mithril Bham]

So many variables. Such different needs. I can't remember all the tenders I have used but since one of my favorite things to do is anchor then explore by dinghy I want something fast that can handle rough water.
Have AB with 20hp Honda 4 stroke. Planes well with two. Three a bit tougher but I weigh a lot. Had 14 ft Novurania with 50hp if you really want to get around with a few people but that is moot since it seems that you are looking for lightweight.
I don't know why anyone would buy a 2 stroke at this time. Real RIB for sure if inflatable. Aluminum great. Patching gets old.
I would go for 12 ft with 20HP four stroke.
Davits help so engine doesn't have to be removed.

[MicHughV]

As above, I think an issue to be considered in this quest, are the davits. Most dinks, these days are carried in davits. I see some that keep the engine on the dink while in the davits, probably not off shore, but certainly while island hopping.

I have tried putting the dink on the davits with engine on. It wasn't easy, and clearly the one davit wasn't happy about it either, and that was only a 15 hp engine. I only tried it once. Most stainless tubular davits are rated at about 175 lbs per arm. There is some safety factor involved, but I don't know what it is. Factoring in half the dink weight, outboard, fuel tank and other clutter and you will be clearly at the limit of the arm.

To have an engine larger than 15 hp will almost certainly require an outboard engine crane hoist of some kind to get it off the dink or some really stout davits. Then where to put the engine once it's aboard ?

From my perspective, a 15 hp motor is a beast to get on and off the dink and then on the boat. It's two person job, no matter how you slice it.

Finally, the length of boat and shape of stern will also dictate what you put back there. A canoe stern, for example, will be a challenge, as would a really long dink on a narrow transom.

A lot of boats mount solar panels on their davits, this will also reduce the load carrying ability of the davits.

I had no davits on my first boat, the dink had to come aboard via the halyard and then lashed down, upside down. I was young and foolish then.

I'll be curious to see the final outcome of this thread.

There should be an "age" column involved.....stuff I could do when I was in my 20's are a tad more challenging these days.

[Adelie]

Originally Posted by MicHughV

I've had a variety...

9' Fiberglass dink with 2 hp Suzuki 2 stroke. limited to 2 people and 4 mph....slow, but good on gas, getting in and out from the water only for the young and fit. Engine can be picked up with one hand.

11' inflatable with plywood floors and 15 hp Suzuki 2 stroke.....too much power for such a dink, floors want to fold. Engine too heavy, can zip along at prodigious speed, but very squirrelly. Excessive gas consumption. What's the most number of adults that could get on a plane? Maybe with some gear or a kid?

11' RIB with 15 hp Yamaha 4 stroke. As above, plenty of zip and power, maybe too much. Engine is heavy and difficult to attach or remove from dink in water. Also a gas hog.What's the most number of adults that could get on a plane? Maybe with some gear or a kid?

11' RIB with 9.9 hp Yamaha 4 stroke...basically the same engine as the 15, but with slightly slower speed. Slightly better gas consumption, but only slightly.What's the most number of adults that could get on a plane? Maybe with some gear or a kid?

11' RIB with 8 hp 2 stroke Yamaha. By far and away my favorite combo. Enuff power to get 2 people up on plane....with groceries, a bit of a struggle, but can do it. Engine can be lifted with one hand. Good gas consumption. It's not made anymore, but my fav.

Like most, I favor more power, but it comes at a cost in weight and fuel consumption.

the 15 hp plus is great for getting out to the reefs for some diving, but in an anchorage, I find the 8 hp more suitable.

See above followup questions in RED.

[Adelie]

Originally Posted by Mithril Bham

So many variables. Such different needs. I can't remember all the tenders I have used but since one of my favorite things to do is anchor then explore by dinghy I want something fast that can handle rough water.
Have AB with 20hp Honda 4 stroke. Planes well with two. Three a bit tougher but I weigh a lot. Had 14 ft Novurania with 50hp if you really want to get around with a few people but that is moot since it seems that you are looking for lightweight.
I don't know why anyone would buy a 2 stroke at this time. Real RIB for sure if inflatable. Aluminum great. Patching gets old.
I would go for 12 ft with 20HP four stroke.
Davits help so engine doesn't have to be removed.

I'm trying to get real info on what is the minimum hp to plane various types of dinghies with various numbers of people.

My sense it that people cruising buy 2-stroke because that's what's available outside of the USA and Europe, because there are few places to get 4-strokes worked on outside of US&EU, because 2-strokes survive dunking better than 4-strokes, because they have slightly better low end torque for the hole shot to get on a plane so they can keep the faster prop and still get up fully loaded.

[wingssail]

Originally Posted by MicHughV

As above, I think an issue to be considered in this quest, are the davits. Most dinks, these days are carried in davits. I see some that keep the engine on the dink while in the davits, probably not off shore, but certainly while island hopping.

I have tried putting the dink on the davits with engine on. It wasn't easy, and clearly the one davit wasn't happy about it either, and that was only a 15 hp engine. I only tried it once. Most stainless tubular davits are rated at about 175 lbs per arm. There is some safety factor involved, but I don't know what it is. Factoring in half the dink weight, outboard, fuel tank and other clutter and you will be clearly at the limit of the arm.

To have an engine larger than 15 hp will almost certainly require an outboard engine crane hoist of some kind to get it off the dink or some really stout davits. Then where to put the engine once it's aboard ?

From my perspective, a 15 hp motor is a beast to get on and off the dink and then on the boat. It's two person job, no matter how you slice it.

Finally, the length of boat and shape of stern will also dictate what you put back there. A canoe stern, for example, will be a challenge, as would a really long dink on a narrow transom.

A lot of boats mount solar panels on their davits, this will also reduce the load carrying ability of the davits.

I had no davits on my first boat, the dink had to come aboard via the halyard and then lashed down, upside down. I was young and foolish then.

I'll be curious to see the final outcome of this thread.

There should be an "age" column involved.....stuff I could do when I was in my 20's are a tad more challenging these days.

Yes, a 15 HP motor is a two person job. But it does not have to be a "beast" to get on and off. We hoist it amidships with a spin halyard and a large primary winch. It is extremely easy other then the need to time the roll of the boat if you are in a rolly place. Still not a problem.

Once the halyard lifts the motor onto the yacht we drop it down the forward hatch onto a bracket. This too is easy, but you had to plan ahead when you put together the boat: You'd need a place with a bracket down below. Some folks put the outboard motor bracket on deck near the mast. That is an easy lift on or off.

As for davits, many boats now have an arch and davits but it is not a good place for that extra weight. Few people who've crossed oceans would continue to advocate that approach. Our method is a fully inflatable dingy which can be deflated, rolled up, and stowed below. MUCH MORE SEAWORTHY THAT WAY!

Often we are in an anchorage and we watch people, usually couples, struggle with the dingy and motor on the aft end of the boat. it is always an issue. if we can remove our motor and then stow our dingy in 15 minutes it takes them 45 min and a lot of swearing. I've seen single handers do it, and it ia a couple of hours of struggle. And the final result is an un-seamanlike situation.

The basic problem is that people want to have a big RIB and a big motor on their cruising boat, and it rarely works out.

[MicHughV]

11' inflatable with plywood floors and 15 hp Suzuki 2 stroke.....too much power for such a dink, floors want to fold. Engine too heavy, can zip along at prodigious speed, but very squirrelly. Excessive gas consumption. What's the most number of adults that could get on a plane? Maybe with some gear or a kid?
2 adults and gear/child

11' RIB with 15 hp Yamaha 4 stroke. As above, plenty of zip and power, maybe too much. Engine is heavy and difficult to attach or remove from dink in water. Also a gas hog.What's the most number of adults that could get on a plane? Maybe with some gear or a kid?
As above, 2, but can do 3 adults with difficulty

11' RIB with 9.9 hp Yamaha 4 stroke...basically the same engine as the 15, but with slightly slower speed. Slightly better gas consumption, but only slightly.What's the most number of adults that could get on a plane? Maybe with some gear or a kid?
As above

[MicHughV]

Wanted to make this observation. With just the significant other on board the dink, we most often stand. This keeps us out of the spray. I have a tiller extension on the outboard, and hold on to rope coming from the bow.
With 3 people onboard, generally sit on the tube for better balance.

[JPA Cate]

I'd like to add to my previous post that max planing speed with two up and in fairly flat water was 20 kn. With our heavy foursome, we could plane, but did not make a note of the speed, but we were able to throttle back, once we got up. However, with a chop running, or into very much wind, it was a waste of time. I normally figure 4 adults at about 800lbs all up. As to size, I'm sure we could get by with a smaller dinghy. However, we use the halyard to get the 15 on and off the dinghy, and Jim can do it by himself, though we usually do it together. We hoist at amidships to the correct height and it swings up higher as he walks it back. Lashings mark the halyard; he sets it on its mount, eases the halyard down, then tightens the motor again, and lashes it to the rail.

Not as agile as previously, we don't launch in over 20 kn. any more. Just feels safer. [25 used to be our top.] We did use our dinghy to go well away from the mother boat for water exploring and diving expeditions. Swimming and skin diving were prime activities.

Ann

[David B]

Zodiac 350 Fastroller (HP air floor). With a 15HP 2T Johnson on the back, it planes effortlessly with two people, and gets up to 20 knts (as checked running along side a skiboat).
With three people, still OK. Four people, they need to be lightweight, and the water smooth, so the boat can get over it's bow wave - otherwise no chance.

Zodiac 340 Fastroller with a 6HP Evinrude 4T. Planes OK with two up. After that, no chance, unless the third person is a real lightweight.

Would always go for an air floor over a RIB. There is some performance pay-off, but not having a big hard dinghy that can't be stowed properly more than makes up for that.

We use a Bravo 12V inflator - makes inflating so close to effortless, it doesn't matter. It has an adjustable pressure cut-out to remove the chance of over inflation, uses a blower for high-volume/low-pressure, and cuts over to a diaphragm pump for high-pressure/low-volume. Nice little unit. There is a larger one available too that I have seen mounted in the garage of bigger yachts.

[Adelie]

Update.
Keep the info coming. If anybody knows people that take hard dinghies out, I'd like a little info from them.

[bongo]

A Walker Bay 8, with a flotation collar, 2 HP Yamaha. Planes with 1 or 2 adults, (need to shift weight around to get on step), (~410# passengers), in calm conditions. The big advantage, boat and motor easily man-handled.

[rslifkin]

Originally Posted by bongo

A Walker Bay 8, with a flotation collar, 2 HP Yamaha. Planes with 1 or 2 adults, (need to shift weight around to get on step), (~410# passengers), in calm conditions. The big advantage, boat and motor easily man-handled.

I'd call this the most surprising result in this thread. I was always under the impression that the Walker Bay dinghies just didn't plane at all.

[MicHughV]

thought I'd put some perspective on dink sizes...so dug these out
fiberglass dink with 2 up...
11' inflatable/wood floors with 15 hp and 2 up....

I generally keep a smallish plastic container in the dink, which contains mask, snorkel and fins and dink anchor gear...plus there is a fuel tank, bailing scoop and other odds and ends...