Ridiculous ? HP for a 10' inflatable?

"Do I really want to or need to plane in the thing?" WANT to? Probably. NEED to? Probably not.

Speed is always nice to have. If it weren't for the portability issue I'd hang the biggest motor the thing will handle. I personally don't think you have that choice; a 9.9 won't push you very fast either if it's laying on the bottom of the harbor. My old 4 hp 2-stroke (33#) will push my dink at hull speed all day with 3 persons. Plane? forget it.

Generally when the going gets rough (windy) you're going to be forced to slow down anyway, so power isn't that big a problem. Current is different but usually you can work your way around the worst spots. Going through a bridge can be a hassle but it'll only last for a minute or so, then you're out in the open and can putt-putt to your hearts content.

Everything's a compromise....

Where in Florida, by the way? For a while I thought you had to run Hells Gate with the thing.
 
Just my 2 cents worth, but I have a 10 1/2 foot Zodiac with a hard floor (you know, the 4 plywood sectionals). I had the same concerns about weight, manueverability, etc. I went with the Tahatsu 3.5 hp, 2-stroke for the weight. I didn't really want the storage or weight problems of the 4-strokes. I don't need to plane (I only use it for getting me (at 250#s, the 90# lab, the 20# chug, and sometimes the Admiral (not even going there about her weight) to shore for the dogs' benefit. So far, I have not experienced any trouble in getting to where I needed to go. Granted, it's not the fastest vessel I've been on, but it does the job, was less expensive than other options, and less strain on my aging back. I have not used the dink in strong winds or current, but if I had strong winds or current, I would likely not be on the hook at the time.
 
I have a 10' 2" achillies with a 9.9 Mariner 2 stroke and with 2 people on board we can use the raft to go tubing [ children under 100 lbs.]
Since I own a trawler, its the fastest boat I own. Oh, by the way 3 gal. a day.....
 
I'd love to go fast but I'm with cmagic99. I have a 99 lb Admiral and she can't lift a big outboard and get it safely on the inflatable from the swim platform. And sometimes she wants to take a ride without my help. Or without me. We have a tiny 1.2 hp motor that has provided hundreds of hour of fun for us. Sometimes, at the places we visit, it's nice to motor along slowly and quietly. The Admiral is a bird watcher so the quieter we are the better.

To each is own, I guess.
 
We've used a 2.5 Nissan on a Zodiac 8'6 for years. As a small woman, I'm able to carry it and easily mount in on the transom. The boat doesn't "speed" with 2 of us on it but it is more than adequate for our uses.........fishing, exploring and getting to shore. This year we'll be using a 3.3 or 3.5 Merc (can't remember which it is) but don't know if it will get us going much faster.
 
Achilles 9'6" with plywood floor and inflatable keel, rated for 8HP max. The motor is a 1963 Johnson 10.0 HP 2-stroke at about 73 lbs., if I recall. The boat planes easily, runs fast. With one person, open throttle on a couple of inches of chop could get out of control real fast. On calmer water, full throttle is a kick and I feel like Howard Arneson. The boat planes with two adults and a 6 gal fuel tank strapped down near the bow. I haven't tried 3 on the boat yet, except for short taxi rides between boats. A Doel-Fin on the lower unit and aluminum battens on the plywood floor were useful mods.

An overhead pulley, rope and hook mounted on one of the marina posts make engine handling easier.

This all reminds me: I haven't cleaned up and used that engine in over a year. Something else to maintain and clean up during the next few weeks.
 
Six HP at 55 lbs may be an ineffective compromise that may not gain enough for the weight tradeoff. Even with the high pressure inflatable floor and keel, planing may be a moot issue in the 6 hp/55lb range.

Looks like the choices are:
3.5 HP Tohatsu 4 stroke at 38 lbs above water exhaust NEW $829
6.0 HP Tohatsu 4 stroke at 55 lbs below water exhaust NEW $1225
7.2 HP Merc 2 stroke jetted to 9.9hp at 65 lbs 1975? rebuilt $1000
8.0 HP Yamaha 2 stroke at 60 lbs, below water exhaust used $1450

The trade off is weight for power, there's a HUGE difference between 38 lbs and 55-65 lbs over my transom to the swim platform and then setting it on the dinghy. So now I'm thinking either go with the 3.5, keep it to hull speed, relax and enjoy and save the weight issues OR go with the rebuilt, upgraded Merc and maybe have the ability with my high pressure floor and inflatable keel to not only get out and have some fun but perhaps even also do a pull toy? Am I being realistic or ridiculous?

RWS
 
I'd vote for the lightest, high HP you can handle (say 5hp 2-stroke).

I have a 8.5' wood floor, inflatable keel, rated for 9.9. I am running a 5hp merc and have a product called 'lifters' mounted to the transom (great product).

It will plane my wife and I, but not with my 6yo daughter, dog, cooler, etc.... The 5hp is plenty to overcome currents, just enjoy the scenery :) The 5hp will push a full load fast enough to make a significant wake, and if I decrease the prop pitch would plane with a full load - so it's more than enough.

BTW - the internal gas tank vent closes, and there is a fuel shutoff - so you will get the same amount of raw fuel smell from internal or external tanks from the carburator. (I have both and never use the external anymore unless I needed to cover 40 miles or so, so I never use it :)
 
You are not going to be able to pull toys beyond hull speed, not much fun. I had a 10 foot RIB with a 6HP 4 sroke which I could get on plain only when alone in the dink. I now have an 11 foot RIB with a 30HP Honda, I can only get toys pulled to any speed that is fun if the rider is flat on the toy, meaning no limbs in the water or sitting in the center of a ring and buldging the the bottom out. Also had to find a PVC toy that has considerably less drag then the nylon covered toys. Otherwise it was almost impossible to get on plain and the engine got terribly hot and this dink will do close to 35Mph with the Honda, but inflatable toys have a huge drag. I would also be concerned about the strain on the transom of an air floor dink.
 
Dominic,

Thanks for your good point on the transom. I never considered using the dink for this purpose, but now the idea is intriguing as it opens up another opportunity for fun stuff on the water. I would be better off to attach bridle rings with flat reinforcing washers throughbolted directly to the transom.

The rebuilt 9.9 mercury at 65 lbs is sounding better and better, but is this 65 lb outboard worth the ADDITIONAL 27lbs ?

RWS
 
I use a merc 3.3 on a 8'6 west marine,I had a 8hp on an 11' and the winner of the 2 is the 3.3.everytime I had to put the 8 on I thought either me or the motor were going for a swim. my 2 cents
 
I'm at 38 lbs on the New Tohatsu 3.5 hp or 65 lbs on the Merc 9.8 jetted and valved to 12 hp.

I KNOW the Merc will be MORE FUN, IF I can keep it out of the water !
 
I have 2006 9.9HP 4 stroke Suzuki on 10.6" inflatable and wouldn't mind to have 15HP :)
 
RWS,

I've watched your posts about the dinghy and I know you have your mind made up about inflating and disassembling the dink each time. I'm afraid you are going to learn the hard way. I had the same idea and it is an incredible pain in the rump to do it. That, of course, will affect your motor choice. I had an 10'-6" Achilles with a plywood floor and a 9.8 HP two stroke engine. It would plane with 500 lbs in it, but I always wished that I had 15 HP. With 6 HP, I don't think you are going to be able to plane with the two of you and the dog in it, so you may want to save the weight and go with a smaller engine. The other advantage of Weaver davits is that when the dinghy is clicked into them, it is much more stable for putting the engine on to the transom.

Your dinghy experience may be like a big boat experience. As soon as you get it, you may start shopping for the next one :-)
 
quote:
Originally posted by AbsoLoot

'......
Your dinghy experience may be like a big boat experience. As soon as you get it, you may start shopping for the next one :-)
Click to expand...

So start with a 9.9 merc 2-stroke and the upgrade with a 15hp upgrade kit when you feel the 'need for speed' ;-)
 
I'd go with the Johnson 6. I've had one since 65. Still have it, and no problems ever!
My Johnson 6 would make my 13' Metzler go Six Mph.
With a huge load is was a bit slower, not much though.

Looking at the speed of an inflatable under a bridge against the current, if the current is more than Six mph, your gonna go backwards!

That boat weight dont mean much. it's the load that brings the hull down into the water for more drag that means something.

Those other motors are cheap substitutes for the Johnson.
 
Have to agree with AbsoLoot. I bought a nice inflatable with the thought of letting the air out of it and storing it in that nice bag that came with it. First of all, it may get limp, but it doesn't completely deflate when you open the valves. You have to suck the air out with a pump. Where do you do that? In my case in our cockpit, after dragging the thing up onto the boat. That got old fast. Solution? Pump the thing up and store it on Weaver Davits on the swim platform. That has worked OK, in fact much better than I thought. The davits work fine for releasing and attaching. Gluing the onto the inflatable is another story but it can be done.

Bill
 
Hello All and THANKS for all of your comments thus far.

We ended up with a 10'6" Hypalon dink with a high pressure floor and inflatable keel.

It was the last one in stock, a floor model and we helped and watched the store personnel take it down. I really didn't expect to see it go back into the bag, but to my surprise, in less than 10 minutes it was rolled up against the transom and neatly in the bag.

We got the dink home and decided to see just how difficult it would be to assemble it ourselves, so we did it in the family room. After figuring out how to operate the foot pump (it's easier when a 12 year old runs it !) we had it together in about 12 minutes! Put all three of us and the dog into it, took some pix with the camera timer and then disassembled it and rolled it up even smaller than the store guys did in less than 10 minutes! I was planning on getting an electric pump with a vacumn function, however that really isn't all that important now.

I'm REALLY GLAD I took the advice on this forum and got the air floor and keel Hypalon model.

In actual use I suppose when we're done, we'll rinse off the salt water and let her dry off inh the sun on the foredeck so we don't ever roll her up wet before storing her.

As far as the engine choice is concerned, looks like the modified 2 stroke Mercury 110, a factory 9.8hp 11 ci, twin cylinder unit with modified reed valves, spark advance and carburetor to achieve 12 hp is the choice. While 65 lbs IS a compromise, of course I'd prefer to be at 38 lbs but I feel with premade lines with snap clips attached to the carry handlesrun over the top of my transom through the hawsepipes to the rear cleats, I can keep the powerhead ABOVE the water line if I ever lose hold of her.

I think there will be more to gain with the additional HP including perhaps some fun stuff with the kids. I'm still under 50 (barely) and in good enough shape to deal with the weight.

Your ongoing comments on these choices are appreciated.

I'll do a new posting with some actual data and observations once the project is complete.

THANKS !

RWS
 
UPDATE NOVEMBER 2012
==============================

RIP 1976 Mercury 9.8 110 Series at 65 lbs

She starts consistently on the second pull, but is simply not worth putting any serious money into a lower unit on a 1976 Merc

Speed is fun on our 10.5' hard air floor dink with inflatable keel.

We use a St Croix mini crane to safely load the dink engine from the lazarette to the dink.

So, Yamaha 2 stroke 8 HP at 60 lbs

or

Yamaha 2 stroke 9.9 HP at 80 lbs

(I can change the reed valve plate on the 9.9 to get 15 horse....

But an 80 lb dinghy engine.........

even with the mini crane, seems like a lot of weight to heft around.

Your comments are appreciated!

RWS
 
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