My New Inflatable Needs a Motor, But Which One ?

[Adeline]

Achilles LSI-77 airfloor. 7'7" and 60#. Capacity 770# Rated for 4hp. I'm thinking that the motor will be stored inside the dink atop the cabin. So many questions. First, is planing possible or even desirable ? If yes, will a 4hp do it ? A 4 is about the heaviest(40#+or-) motor I want to lug around. An integral fuel tank is common on the little motors but will they leak gas if laid on their side ? They typically have a screw-down vent on the fuel cap. Can I trust it ? I've read that the Honda 2s are picky about being laid down at all. Something about oil flowing back into the carb. Is this true ? They are available with or without a centrifugal clutch. Which is better ? I've heard that they're really loud. Is this true ? The little motors I've looked at usually have no reverse. Some have no neutral either. I guess that they're started in gear. I can think of alot of reasons why I don't like that. Most have throttle control on the motor. I want throttle control on the tiller, like the honda. I DID find a 4 horse motor that I REALLY like. The OMC Deluxe 4 (out of production) has F-N-R, a twist-grip throttle, and two cylinders(smoother). But it weighs 50 pounds. Too heavy. I'm planning on buying used and will consider anything since they went to breakerless ignition. i.e. early 70s. I've never owned a portable outboard so I hope others will advise.

[thataway]

I am a bit behind the times--in that I still have a 3.5 hp 2 stroke. It has a self contained tank, which does not leak (shut off the fuel, run fuel out the carburator on shut down, and shut cap vent). I do carry an extra one gallon can in the dinghy. I think that in a small dinghy that a large 3 or 6 gallon tank is in the way.

I have made a mount which fits on the side railing--or on the motor mount of the kicker. But it can lay safely on the floor after the water is drained out.

This motor has neutral and foreward. No reverse--the motors rotate thru 360 degrees, so you have full thrust in reverse--and this works very well.

I do think that a neutral is very useful. I owned the Honda 2 hp with centrifical clutch--and didn't keep it long. I felt that it is under powered for an inflatable (it may only happen occasionally, but if you get more than 25 knots of wind, a small motor may not be enough to push you against the wind---I almost learned that lesson the hard way! The centrifical clutch had too rev up the engine too fast to engage, I like to putt along or idle up along side a boat--the clutch made this more difficult for me--others may have had a different experience--and in general I think that Honda makes a very good motor--just this one I don't like.

I have a dinghy slightly larger than yours with an air floor and am still using the 3.5 hp--it is enough but light enough to carry easily or pickup and put into the boat. It is big enough for a kicker for the 22 in a pinch or even the 25 (where I have a bracket for it, which does not reach as deep as the bottom of the hulls, so I have full thrust in only 15 to 17" of water.

Good hunting!

[Larry H]

Pete,

I had an 8'8" Achilles like yours and my 2hp Evinrude 2-stroke would almost, but not quite, plane the boat with one person.

I would recommend a 3.5 or 4 hp with at least a neutral. It should plane the boat with one person, maybe with two. I carried the 2 hp on the 22 cruiser's transom, tilted up.

A two stroke would be lighter, but you would have to mix the oil into the gas. The two stroke would also smoke slightly, but has no crankcase oil to check or change, and you can lay them down on either side.

[JamesTXSD]

We have an 8.5' slat floor inflatable, also rated for up to 4 hp. I was looking for the easiest, lightest solution - we have a Merc 2.5 2-stroke. Forward only, no neutral or reverse; neutral would be nice, but we just hit the kill button. Pull once and it fires right up, and you're off and running again.

I have been told (don't know that this is true) that no one is making small 2-strokes anymore. I really enjoy the lighter weight (we had a Honda 5 that was a beast) and the fact tha the motor can be stored laying down (on any side). With the gas petcock and vent closed, it has never leaked.

Our slat floor won't plane; 2.5 hp has been enough motor to move us around. We carry two 1-gallon gas cans: 1 mixed, 1 not mixed (the motor has an internal tank only). For short trips to shore, I just check fuel before we head out, top off if necessary, and don't carry gas in the dinghy. Mixing oil into the gas is no big deal; I buy the oil that comes in a container with a measured spout on the side. Easy.

There are many places the C-Dory can go that you won't need a dinghy. However, there have been plenty of anchorages this trip where the only way in was the dinghy. It takes a few minutes to get it down and ready to go, but it is well worth it.

Best wishes,
Jim B.

[Flyer]

For long distance exploring you will probably use your C Dory. They have shallow draft and can cover a lot of ground.

For poking around do you really need to plane? That inflatable will probably not plane given two average weight adults. It takes more to get an inflatable on plane then a rigid bottom boat.

Value of a lightweight outboard is often underated and it is very important. A lightweight outboard will get used more often because it is not a chore to change out.

I have a 2 cylinder OMC and its going on sale this spring, its the lightweight version F-N weighs about 33 lbs. The smoothness is overated. That design is getting old, new technology is engineering out the differences in terms of vibration. There is not that much difference from between a single and twin on an inflatable with as flexible as an inflatable boat would absorb most of the additional vibration if its even there. Our 4 hp 4 stroke Yamaha has about the same vibration level as the OMC.

Neutral is a very good feature, it gives you a lot of control. Reverse is nice.

I really like the 2.5 hp Yamaha and used one for a season, a little light for our current use but for just poking around on a small boat it would be great choice.

[drjohn71a]

OK,,, Time for craziness..... have you guys seen that little Torqeedo, electric outboard? The 2 hp lithium battery sits where a normal outboard engine sits and an extra battery could easily be slipped on and off. I think it weighs 25 lbs... The 4 hp uses separate batteries, so they would be heavy.

I was thinking of using that 2 hp model with an extra battery on an inflatable for my TomCat, but just opted for one of the new Hobie Mirage Kayaks. The Mirage is a pedal drive based on peguin's wings and propels you more effeciently than a paddle. I got the Adventure Island model - a convertible, tri-hull sailing model. As such, it can be pedaled, paddled, or sailed. The center kayak hull is 62 pounds, so not hard to load when apart. I'm trying to figure out Yakima rollers on the bow rail and fore cabin rail so I can just roll it up and over.

Anyway, The Torqeedo folds into a small carry bag and has no battery acid/gas problems to deal with. I think it lasts 6 hours at slow speed and only about 2 hours on higher speeds. However, the battery for it is small and two would get you 12 hours on slow and 4 on higher speeds.

I contacted the company about charging it while cruising and they said a simple, plug-in inverter would charge the Torqeedo lithium battery easilly while you cruised.

John

[Doryman]

Some observations (I bought an Alaska Series dinghy at the SBS and have yet to buy a motor for it):

1. You can't buy new 2-strokes in the small hp range any more due to EPA regulations.

2. For me, my choice is constrained by the need for a long-shaft motor. Otherwise I would get the Yamaha 2.5.

3. The 20# Honda 2 hp was recommended by Jim King of Alaska Series but I also am listening to Bob Austin's warnings about it.

4. At the moment I am leaning toward the 38# 3.5 hp Tohatsu/Nissan which is available mail order. I would deploy it with a davit, either Garhauer or Ace.

Warren

[Jazzmanic]

Warren,

After reading a prior post by you about the requirement to have a long shaft on the Alaska Series inflatables, I went back and looked at the owners manual online. It didn't mention that a long shaft was required, except for 2 models, the 480AR and the 500AR. So where are you getting your information that a long shaft is required?

I'm concerned because I bought a Suzuki 2.5hp short shaft last summer and it seemed to work fine for me.

Peter

[Doryman]

[Best Day]

How fast do you guys think the 3.5HP 4 stroke would push a 22CD? Is it possible to use it as a kicker and tender motor?

Bill

[Jazzmanic]

Warren, thanks I see the "L" now. However, last summer, I had a friend who's probably 6'2" 240 lbs in the dinghy with me (at 5'5" 185 lbs) and the little Suzuki 2.5hp moved us around just fine. We were in Lake Washington and not in the salt somewhere. I did notice that the engine sat a little high but it wasn't cavitating even with all that weight. I guess I could trim the transom a bit but otherwise, it works fine. By the way, we have the 240T model.

Peter

[Larry H]

Warren,

By measuring the transom of your dingy, you can tell which length motor you need.

Measure vertically at the center of the transom from the top edge(where the motor sits) to the bottom of the boat.

If the measurement is 15 inches, get a short motor (15 inch leg), if the boat is 20 in tall at the transom, get a long motor (20 inch leg).

The anti-ventilation plate (cavitation plate)(located just above the prop), should be even (within 1 inch) with boats bottom when the motor is clamped to the transom.

A long motor on a short transom(15 in.) will cause excessive bow lift, and can roll(flip) the boat in a turn.

A short motor on a long transom (20 in) puts the prop behind the transom where it can suck air (ventilate).

I looked at the boats web site and I think the 4.0 L is an error.

Its unlikely that the smallest boats would have a 20 in transom.

[Alasgun]

Im thinking a 400 Hp 350 chevy coupled to a belt drive reduction unit and turning a 60 inch warp drive prop would be just fine. It might burn more fuel than the 4 Hp but you would get there faster so it would probably be a wash on fuel burn. Have you ever blown up a balloon and turned it loose for your Grandkids to watch it zoom around the room? Think of the look on their faces when you show them the Pa-Paw version and ask if they want a ride!
Mike on Huda Thunkit

[Doryman]

Thanks, Larry H, for the good advice. I will wait until the dinghy actually arrives and then figure out what to do. This dinghy is donut-shaped, not U-shaped, so the transom is attached to the top of the stern tube. Hence it is higher than a U-shaped boat. Just wanted to make sure you picked up on that.

Peter, your comment about the weight in the boat made me realize that my not-inconsiderable weight might be the ticket to make a short-shaft work with this dinghy. I'll have to do the measurements both on land and in the water.

Warren

[thataway]

Best Day,
I have used a 3-4 hp to push a C Dory 22; in calm water it will push the boat 3-4 knots. As long as you are below the sq rt LWL, it takes very little horsepower. I pushed a 62 foot, 60,000 lb boat with a 4.5 hp outboard at 2.5 knots. Lots of other examples if you wish. I routinely used the 3.5 to push a 30 foot express cruiser across a sand bar. I could make headway in up to 20 knots of breeze.

One of the advantages of a 3 to 4 hp dinghy motor is that it could push the C D 22 as well--so you only have one extra outboard to worry about. If you want to go 5 knots or more--then go with an 8 to 15 hp.