Outboard size for our new tender?

Below is a pic of the new 8ft hard dinghy I just bought today. My question is if an 8 HP Nissan is too much motor for it? I’m 6’2 230. I wont see the next sunrise should I divulge my wife’s weight even if I knew it but she is 5’11”. I share that because we are fairly large people. I also have an almost new Honda 2 HP I bought at an opportune price and time but I just don’t think that is any where near enough HP for us and any cargo when we start looping in about 10 months.

The dinghy(make unknown) can be sailed or rowed as well but my plan is to have all three options available. I can test it out soon with the Nissan HP but I’ve got someone who wants to buy the 2 HP Honda, so if the consensus here is “ no way that’s enough HP for your needs then I’ll probably make that deal.

2hp Yamaha or 21/2hp four stroke probably 10lbs heavier.

And instead of more hp I’d be thinking about more boat. Two big people are too much for that little boat. Get an old Livingston used. Then get an 8hp 2 stroke OB.

I have a slow speed boat that would be excellent for you but it’s 12’. Bright side is 2-3hp will push it even with your weight.

Looks like a rather displacement hull... how fast will it go? If it can't get up on a plane, perhaps 2 hps "might" get the job done.


But, if you wanna skoot a bit, with a boat. motor and pax weight in the (guessing, too) 500 to 600 lb range, you'd probably need 15 or 25 hp.


But, what's the boat rated for?

Nice looking dinghy, but it's not going to go fast. 2 HP should be plenty.

That looks like a great sailing dingy. A good candidate for electric power.
Sorry JMO, hope I am wrong.
The 2 HP will work, but 2HP or bigger gasser needs to be started which means 230 lbs of you plus motor and you may swamp it.
Speaking from experience on that thought

I'd go for a 4hp. Tohatsu make a good reliable engine. My 10' dinghy on my sailboat has a 6hp Johnson and it's too heavy to manhandle onto its rail mount without using the main halyard. 2hp seems worse than a squirrel tethered to your bow line.

We're not little people either, 11 ft (inflatable) dinghy. We have a Yamaha 4hp, but I would definitely not go any lower. Scoots fast enough, but just. I'd go 6hp or higher but then the motor is too heavy to easily handle and for long runs we need to dismount and carry the dinghy on the bow.

I am a big guy, that wouldn’t be the dinghy I would get for 2 bigger people if I were going to use it regularly. Once in a while maybe but not regularly. Particularly if you plan on carrying supplies. Get a good inflatable and adequate power, IF you have a way to hoist it and the motor.

The 2 hp will be fine if the shaft is long enough. There should be a load capacity plate on the boat. The 8 is way over the top. Does the boat have a motor mount?
The similar shaped West Marine Classic hard dinghy is 2 ft longer and only rated for 2 hp.

I don’t know what that dinghy is but some comparable max load (people, motor, gear) of some similar 8’ boats:

Fatty Knees 475, max hp 2
Trinka 450, max hp 2
Bauer 465, max hp 2
Dyer 465
Puffin 425

2-4 hp is fine and I believe 8 is too much for these boats. I have a Torqeedo for our Fatty Knees that pushes the boat and a total payload of around 410 lbs +/- at 4+ knots without fuss. Burns far fewer electrons at 3 knots though.

Your dinghy looks to have a similar bottom to mine. The hull isn't going to plane. 3 to 4 knots will be very efficient. Above that the bow will start to rise dramatically and the stern will squat with a big wake. More than 2 HP will accomplish very little.

I recommend the Epropulsion outboard. It's about 3 HP and will get you 15 to 25 miles per charge depending on the speed. They offer 12 VDC, 120 VAC, and a solar panel for charging. Great motor; essentially zero maintenance; no need for gasoline on the boat.

https://www.epropulsion.com/



Ted

I agree with those saying that hull form will never go very fast. So I'd try the 2hp (being that you already have it) and see what happens. There's a good chance it'll be enough. If it's not, a 3.5 or 4 - 6hp will be (and any of those will weigh less than the 8hp, assuming all 4 strokes).

THANKS to all of you.

Wow I do love this forum! Post a question….. go to bed….. get up on a beautiful but cold morning with nothing winning out over pouring a cup of coffee and reading close to a dozen well thought out appreciated responses.

A few of you point out that given our sizes this one might not be practical for the two of us PLUS provisions, etc when cruising. I’ve already bought her but not having buyers remorse given I LOVE making “Classic boats with good bones” beautiful again. Plus not too complicated woodworking projects are fun too so the fact I’ll need to make mast, daggerboard, tiller, rudder I welcome too. I only paid $650 for it so I’m pretty sure I can’t really go wrong on this.

I’ll repair spiderweb crazing, fair, paint, varnish, then test her with both my wife and me aboard and maybe a few bags of groceries to boot.

Regardless of the outcome of this and my love for making “ cool old floating things new”, I’ll enjoy this process regardless of the test trip outcome.

2 HP is plenty for that dinghy, more power won't be able to push it any faster with that hull shape and it would just weigh more. With that round bottom, I would want to ensure that you have a good railing on your big boat to stabilize yourself and carefully step into the center of the dinghy. It is hard to get a feel for the scale of the boat but it does look small for two large adults and a load of provisions. I would start off with a practice run with oars only and warm weather. Capsizing while loading/unloading can damage your ego but drowning an outboard motor in the process would really add to the sting.

i agree with the points Gdavid made. that skiff will be very tender. if you don't stay in the center of it when boarding it will flip you out in the blink of an eye.
i tried a very similar dinghy to tow behind my sailboat as they have almost zero drag. i ended up in the drink the first time i got in it. it was super easy to tow, but really impractical for me and my wife. and we're weren't exactly big either, maybe 275 pounds combined.
i much prefer a wide, stable dinghy.

What about this?

One of the first replies on this chain to my question referred to a larger dink that he uses. In discussing all of this just now with a friend he suggested I look at a boat for sale near him that is a Cape Dory 10. It’s completely redone and unfortunately priced accordingly. That would negate me doing my own restoration which I would have enjoyed, but I would still have the option of sailing, rowing, auxiliary as well as additional payload. Is the consensus among you folks that an additional 2 feet would make a big difference in what we could carry in addition to ourselves? Would that help with the tender nature of a tender regarding stability?

If you are content on keeping that style and size dinghy, realize it is going to be cramped and is not going to plane and 2-4 HP should be plenty. You also might want to consider an electric outboard in that size. If so, I'd recommend looking up ePropulsion.

Capt, I would prefer the one you have to do this.
https://vimeo.com/225766000
IMO 2 feet longer but just as tender, so no difference for your OB question.

Why I have an inflatable> I can step off the swim grid on to the pontoon and step into the dink. I got tired of stepping to the middle.

For comparison, an 8’ Trinka has a capacity of 450 lbs while the 10’ Trinka is 550 lbs. Do you need that much more for your intended uses?

If you want to sail, row and use it as a tender, it’s an ideal type of boat unless you also want to go fast. RIBs and floating refrigerator doors don’t sail or row as well.

My wife, me, dog and gear in our 8’ dinghy all the time. Plenty of room to row and no, it doesn’t feel cramped to us.

Round bottom boats like these have less primary stability that makes people call them tippy and unstable. However, they have great secondary stability and while heeled, they will resist heeling further. I can nearly stand on the gunnel without capsizing. Yes, it is best to step to the center of the boat when boarding but, that’s what I learned a long time ago about getting in any small boat. People get wet not because of the boat’s instability but due to their own lack of awareness and lack of balance.

We have a 30 ft Echells. A 2.2 hp Honda pushes it at about 5 knots max in calm water. The same engine (air cooled) would push your dinghy to about 4 knots. Treat it like a canoe step to the center. You have an engine which should work nicely. The 8hp is too heavy for your 8 footer IMO. I have a similar design dinghy that I used with my sailboat for 30+ years with with close to 400 lb passenger wt with no problem. Lots of times it was rowed as putting and engine on was more difficult than to rowing. A RIB and a bigger motor if you what to go faster 15 hp+ would work depending on the boat.

I have the 8' West Marine dingy of similar hull shape and rating. It's very marginal for two full sized adults, I would not want the extra weight of a motor on it with two people. I row. It rows easily, a lot more easily when I'm by myself. Rowing is a pleasant activity most of the time, and it's good exercise, leave the motor behind.

2savage said:

I'd go for a 4hp. Tohatsu make a good reliable engine. My 10' dinghy on my sailboat has a 6hp Johnson and it's too heavy to manhandle onto its rail mount without using the main halyard. 2hp seems worse than a squirrel tethered to your bow line.

Click to expand...

Sorry but not so.
My post #2 is w 4hp at 1/3 throttle and a much bigger boat.
Only reason I didn’t say 1hp is that few if any are available.
Look at sailboats. Big and many tons heavy w about 20hp
Water passing under the stern flows gracefully. Very little drag.
Square submerged stern/transom MASS turbulence and drag.
Also read post #8 again.

I love my 10' aluminum RIB. With the 15hp 2 stroke, it will do 20+. Great for exploring. I also have a 2.5hp two stroke for easy mount/dismount for those quick trips ashore. A 10' rib will float four folks of your size easily and as Soo Valley mentions, you can step aboard more easily. At 275# much more care will be required, of course.


RIBs' don't sail (except twirling at the end of their painter in 40kt. squalls) They are useless to row, but if rowed going astern it's do-able. (the rounded bow becomes the stern, exiting the water smoothly)

Nice looking little rowboat! With that transom it will also take a small outboard.
8 hp is WAY TOO MUCH.
I got a 9' whaler with a 6hp outboard with my own boat. I already had an inflatable with a 15, so the whaler was excess and had to go. Before selling it, I put the 15 on it. That combination is not likely any more dangerous than your 8 on 8 ft. At 1/2 throttle, that little whaler was airborne. It porpoised so much I could hardly hang on. Good thing my wife didn't see that experiment! You might not get airborne with your hull shape, but you would have the same lack of control at any throttle setting above hull speed. Anything over 4 hp is more than you can use.

I see you need a boat with greater hull volume. Consider your boat … it’s got very little hull volume at both ends. A box would provide you w the hull volume and hence flotation to support you two but a box dos’nt make much of a boat. An inflatable offers the volume too but again dosn’t make much of a boat.

You need something in-between. A B Whaler is good but not much freeboard and worse too heavy. You need something shapely, fairly wide and a bit deep. See my post#2. Notice how full the hull is aft. Then find a boat that’s full at both ends. Kinda like a Great Lakes ore boat … ultra short. Hold that thought.

What about this?

As usual many excellent points were made here and also as usual a few I had not thought of. My main takeaways are.
1. An 8 foot hard dinghy is close to its max payload with my wife and me with not a ton to spare. Thinking about provisions maybe picking other people up to bring back to our boat etc. not real practical I’m afraid.
2. Although stability isn’t a real issue now, at 62 and 61 respectively I suspect it will begin to become one maybe not in the all too distant future.

Here is what I’m thinking now but there’s a part of me that says you really can’t have everything and you need to be more practical than this, however for the reasons I’ll share now I’m not sure why something’s telling me this is impractical?

Even with the inflatable and 8 hp Nissan that came with our trawler, I was leaning towards installing hanging davits on the transom as opposed to using the mast configuration. Why not proceed with that plan, then carry both of them? It’s just the two of us planning to Loop so storage(especially outside) doesn’t seem to be at a premium, then I have a backup if needed, and I (biggest reason I want the hard dink) I have my ability to row and get exercise, plus and mostly, I have a way to daysail around anchorages.

Am I trying to put a square peg in around hole here? Remember, I’ve already bought the hard dink although I do have to fabricate the apparatuses needed to get the sailing option. My thinking is if I need the space, I take one or the other off of the boat depending upon how we feel towards each of the options after some use.
Most folks can probably picture the set up for the Grand Banks 42 Classic, but I’m posting a pic anyway.

I don’t see why not other than if it were me, I wouldn’t want to obscure the transom of a GB. I’m not a fan of transom hanging a dinghy. And, if you’re honest, it could cost a few more dollars for a slip adding to your overall length. If there’s room, I’d likely stow the hard dinghy on the boat deck and deflate the inflatable with it there too. If you then decide to be a one dinghy boat, you won’t have much invested in additional hardware.

As far as stability, my wife and I are in agreement. If we can’t get in and out of our dinghy, we will expect to have other serious issues walking around the bigger boat and on docks, at which time we’ll retire from boating.

Hanging davits are not cheap either as well as the points made by Porgy.

Since like me you like projects..... I found a 12' aluminum V bottom fishing boat that was to long for the Mainship. Cut off about a foot on the back end and fitted the transom back in. Ever buck 100 rivets ?? With a 3.3 Merc. it does fine with 2 aboard. I use the Weaver snap davits and tilt it up on the swim platform. You can step in and mount the motor while still attached so that takes care of the wobblies...

Solly,
I thought about that too.
Yea .. the 3hp will be OK at displacement speeds.
How long was the boat? 12’?
Lund made/makes an 11’ and maybe a 10.
The aluminum boats are very paintable w primers.