Small OB for Inflatable

[bcripps]

Hey Guys… this is a wonderful resource for boaters like me who are, quite frankly overwhelmed by the amount of marketing BS and just want some good, old fashioned practical advice.<br /><br />I’m heading off to the Bahamas next year and have just bought an Achilles 10-foot inflatable as my sailboat tender. It weights in at just under 90 pounds. Now I’m looking for a good 15-hp, 2-stroke outboard.<br /><br />My dingy will be my car when living on the sailboat. It will get daily use transporting groceries, jerry cans of fuel, water, guests, etc. When I run the sailboat aground… the dingy becomes my tug boat. During rough weather, it will be used to lay storm anchors. The dingy will spend hours every week motoring at trolling speed while I fish the reefs.<br /><br />Top speed is important but not so much as reliability. I will be in remote areas so much of the maintenance and repair work will be done by me, and without benefit of a nice work bench and full set of tools. I know there is a Yamaha and an Evinrude/Johnson dealer in Nassau with service departments… there may be other brands represented through out the islands. I will carry my own spare parts with me.<br /><br />To meet my criteria, I will buy new or used… money is not important when it comes to getting the right outboard.<br /><br />I consider your opinions and recommendations most valuable. What do you think?<br /><br />Bryan

 

[solidwaste75]

Re: Small OB for Inflatable

You might want to look at the new etec evinrudes im not sure if they make em in 9.9 or 15 hp but if they do I would check them out before buying..There supposed to have no sched mantenice for 3 years..

 

[JB]

Re: Small OB for Inflatable

15HP seems excessive for a 10' inflatable to me, Bryan.<br /><br />I would go for a lighter engine. . . 6 to 8hp. . . that uses less fuel. I really like the JohnnyRudes.

 

[TOHATSU GURU]

Re: Small OB for Inflatable

A 15 will pop up three adults and some gear and top out 20-23 mph...if you keep the tubes inflated over 3 PSI. If you plan to buy in the Bahamas keep one thing in mind. No warranty in the U.S. You can buy an engine in the U.S. and the warranty is usually honored worldwide(if you scream loud enough), but none of the manufacturer's will honor their own warranty in the U.S. if purchased third world. In fact, most will not even honor the warranty back in forth between Canada and the U.S. As far as brand go's, Yamaha, BRP, Mercury and all the rest will give you a long service life. I would buy what your instinct tells you to.

 

[Pony]

Re: Small OB for Inflatable

I agree with JB....seems like a lot of hp. Whats it rated for?

 

[swist]

Re: Small OB for Inflatable

Tohatsu. Indestructable.

 

[bcripps]

Re: Small OB for Inflatable

Thanks, everyone, for the quick response.<br /><br />I’m not familiar with the Tohatsu or the eTec engines and the available horsepower ratings. My first question though, is how user friendly are they when it comes to repair and maintenance? Will I be able to fix it with a coconut?<br /><br />You’re right about the 15hp being excessive. The Achilles is rated for 10hp and/or a maximum engine weight of 88 pounds. But I feel I need that extra horsepower to get me out of trouble from time to time. As an example: I have a friend who towed his 35-foot sailboat with his dingy across the Gulf Stream and into Bimini when his onboard diesel died. (Damn wind never blows in the right direction when you need it!) He kissed his 15-hp outboard that day.<br /><br />When I run onto a sandbar from time to time, I feel I will need that extra push to muscle my sailboat around and into deeper water. My sailboat weighs 12,000 pounds.<br /><br />I do intend to thru-bolt two aluminum brackets to the dinghy’s transom and wooden floor to help distribute the load.<br /><br />Thanks for the ‘heads-up’ regarding warranty issues. I’ll be buying in the US thereby giving myself the opportunity to thoroughly test everything out and get a handle on taking the outboard apart and reassembling some of the more venerable components. Maybe this too will void my warranty. <br /><br />Is it the consensus of the group that I would be wiser to buy new or did someone manufacture a little workhorse in the past that is simple to repair and outperforms the present day offerings?<br /><br />Thanks again… Bryan

 

[JB]

Re: Small OB for Inflatable

I think putting 150% of rated HP and over weight, too, on an inflatable is a lot more likely to get you INTO trouble than out of it.

 

[Pony]

Re: Small OB for Inflatable

A 5hp increase over the max hp on most any other boat would probably be ok, but I agree with JB. On an inflatable I think the difference would be magnified........<br /><br />Through a little research it seems that "most"(I hesitate to use that word) 15hp motors are actually lighter than the 10hp variety. ( the ones I saw were anywhere from 10 to 15lbs lighter) Regardless of this I still think the increase in horsepower will make such a small boat very unstable

 

[bcripps]

Re: Small OB for Inflatable

I certainly appreciate your concerns but I can only go on what I see… cruisers with the smaller outboards always seem to covet the larger ones and the guys with the 15’s wouldn’t part with them.<br /><br />The weight of the Johnson 15- two stroke is listed at 74 pounds, so at least in that respect, I am well below the weight allowance.<br /><br />Could you give me a little better idea of the type of trouble you foresee? Are you thinking the inflatable will suffer structural damage? Or do you think it will become airborne or flip over? Could this be solved with a prop change where the engine’s power is there to be tapped when needed but top speed is restricted to safe limits?<br /><br />I’ve seen a couple of inflatables flip but it was caused by wave action, in which situation I think the extra power and maneuverability would be beneficial in controlling the boat around and over the waves. I have never seen an inflatable torn apart but I’m sure it has happened; but most likely to old sun-rotted craft that should have been discarded long ago.<br /><br />I did a little research into your (JB) recommendation of Evinrude/Johnson. One thing that seems apparent is that parts are inexpensive and available everywhere. Also, there seems to be a lot of outboard mechanics out there that can work on them. There is even a very detailed general repair site on the web.<br /><br />Thanks for your input…<br /><br />Bryan

 

[TOHATSU GURU]

Re: Small OB for Inflatable

If you have a LSI air floor a 15 hp will tend to deform/buckle the boat until you get on plane. If you have the SPD board model you can getaway with a 15 hp. The only reason that boat is rated for the 10 hp is due to transom weight problems with anything over 47 kg. They have so much stern weight that they are hard to get on plane even with a light load. Since the advent of the pig 4-strokes a lot of the 9' and 10' boats got very conservative with the hp limits. Oddly enough, inflatables don't use the standard CSG formula for determining hp limits...They use educated WAG.

 

[AJ168]

Re: Small OB for Inflatable

I'd go with Johnson, Evinrude, or Mercury. They're the most common so just about every mechanic will work on them and parts are easily found. Reliability is also great. The outboards used by the military are all Johnson or Evinrude so you know that they must be ultra reliable. I don't think that the extra power will be an issue as long as you don't exceed the weight and don't do anything stupid like try to jump wakes at wot.

 

[Snowdrggn]

Re: Small OB for Inflatable

There are a group of people here that run 10-11ft inflatables into extrememly remote areas. We pretty much run 15hp (or converted from 9.9hp) JohnRudes. At 72-74 lbs, the are among the lightest available, new or used. They have proven to be very reliable, inexpensive to maintain, and have easy parts availability at a reasonable cost. You can pretty much carry all the tools you need to totally disassmble one in your pockets. several of the inflatables are rated for 10hp, but are running 15hp. None have shown any problems as the weight of the 15hp is the same as the 9.9hp. As for the transom concerns, the 15hp develops the increased power at a higher WOT rpm than the 9.9hp so the difference is very little during the actual holeshot (where transom stress is highest). <br /><br />As for props.....<br /><br /> For light load and general goofing around I run a Pirhana 10d x 11p that has been drilled to improve the hole shot. For heavier loads, where I am packing extra gear and fuel, I use a 9.5d x 10p OEM aluminum prop. For dragging 200+ pound people around on a kneeboard I use a 10d x 9p set of blades on the Pirhana prop. (which may be your best choice all around for your application).<br /><br /> None of us use air floor boats, so I cannot attest to the issues involving them. Proper inflation pressures are critical to inflatable boats, particularily when running at speed. Also, Smart tabs are an extremly worthwhile investment as far as controlling bow rise, ease coming onto plane, and stability at speed. Personally I wouldn't consider running an inflatable without them after have them on 2 of my own boats.<br /><br />Here are a few pictures showing holeshot, at WOT, and one taken in a canyon on the Peace River in nortern British Columbia.....<br /><br /> Cheers,<br /> Snow.<br /><br />

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[TOHATSU GURU]

Re: Small OB for Inflatable

In general, the problem with exceeding the recommended hp is not power related to structural failure of the transom or even the tubes coming loose from the transom. It's just a weight issue on the stern. Depending on the brand and model, a 9' or 10' inflatable may/will have problems with hole shot...Depending on the brand and model of outboard they use. As Snowdrggn pointed out, in the J & E models, that he and his friends are using, there is not a weight difference. It shouldn't be a problem with one of those 15's. Using Tohatsu as an example, , there is a 34 lb difference between the 9.8 and 15 4-stroke frame. Other brands have a difference as well, although not as great. A planning aid will help and usually conteract the additional weight too. It also helps to move as much weight forward as you can and to sit as far forward on the tube as you can get...It always helps to put your pal with the pudding belly at the bow. <br /><br />Snowdrggn, I noticed you are using a transom mount fuel tank. Did you see an increase in planning time when you switched from a standard tank? We tried those and found that the additional weight back there really caused a problem on the 9's with 5 hp & 6 hp engines. I can't remember if we tried it with a 10' or 11' with a larger engine.

 

[crazy charlie]

Re: Small OB for Inflatable

Most outboards ,9.9hp to 15 hp are the same motor with the carb or injection being different so the 15 seems like a good choice.I would consider getting an extra prop.The standard one will be good for top end speed but you WILL need a "working prop" to tow your boat anywhere at all.My wife and I run a 15 on a 10ft Zodiac and find it great.Quite frankly if I could go with 5 more hp and not add weight I would do it in a second.Charlie

 

[rayjay]

Re: Small OB for Inflatable

I have a 9.9 Johnson [ suzuki ] 4s on one of my River Hawks. The 15 is the same motor with a bigger carb. Same weight, etc, just turns 500 rpm higher. <br /><br />I also have 20 & 25 hp Merc 2s. Same deal. Same motor except for carb. The 2s Merc 20/25 probably weighs no more than the 9.9/15 4s Johnson.

 

[TOHATSU GURU]

Re: Small OB for Inflatable

Here's the current weight on engines produced for 2006. I have included the most current 2-strokes which may or may not be available. <br /><br />Suzuki & Johnson 4-stroke 97 lbs. 9.9-15<br />Johnson 2-stroke 74 lbs. 9.9-15<br /><br />Yamaha 4-stroke 99 lbs. 9.9-15<br />Yamaha 2-stroke 79 lbs 9.9-15<br /><br />Honda 4-stroke 9.9 92 lbs.<br />Honda 4-stroke 15 101 lbs.<br /><br />Tohatsu/Nissan 4-stroke 9.8 81.5 lbs.<br />Tohatsu/Nissan 4-stroke 15 114.4 lbs.<br />Mercury 4-stroke 9.8 84 lbs. <br />Mercury 4-stroke 15 101 lbs.<br /><br />These weights do not include the propeller or oil and are the published weights, except for the Tohatsu/Nissans/Mercury which do include them. The Mercury's are Tohastu's, but have a different engine cover and have the shift handle built into the throttle grip. Ergo a different weight, but the Mercury published weights are not correct. They are actually 84.5 on the 9.8 and 115.2 on the 15. There may be some Mercury/Yamaha 4-stroke 15's still out there as well. Those are right at 101 lbs. for the 15 and may account for the published weight difference. They should really update that site. Also keep in mind that manufacturers lie and weights can change as production changes occur. It would not surprise me if the weights were off by 1 or 2 lbs on each brand. I have seen it go both ways with some being understated and some overstated.<br /><br />Also, no one is has been wrong in any of these posts. Different inflatables with different engines and different loads/loading and what my appear to be minor air pressure differences, will behave very differently in actual application. This is essentially, a whatever works for you topic.<br /><br />P.S. Tohatsu's are somthing like the old British Seagulls in that they were designed to be worked on without any special tools. Like all the other brands today they are more complicated now and coconuts(oil) can no longer be used except to provide emergency gearoil.

 

[Snowdrggn]

Re: Small OB for Inflatable

Elvin,<br /> The transom tank that you see in the picture is a 3 gallon Sceptre unit, I did find a marginal difference coming out of the hole, but Smart tabs pretty much take care of it. The boat tended to go skyward with a 3 gallon tank tied down in the bow and nothing at the stern. What you don't see in the picture of the boat tied to the dock is a Tempo tapered "Bow 6" tank, and a 20 odd pound bag of gear and spares under the bow cover. If I am only running the 3 gallon transom tank it will come out a bit better if if I slide forward in the boat about 6 inches. If you notice the picture of the holeshot you can see the "hole" in the water behind the boat, that is where I hit the throttle from a standing start, and the boat is just coming onto a plane in not quite it's own length. I find that to be quite acceptable. When that picture was taken I had a drilled 10d x 11p Pirhana prop on the motor. With that prop the boat will run at 32 mph (GPS) as shown in one of the other pictures I posted. With the prop drilled as it is, I turn around 4000-4200 rpm on a full throttle hole shot, but once moving the Smart tabs allow me to maintain on plane at 11-12 right down to 11-12 mph. (GPS).<br /><br />The sensation of a hard launch is not unlike getting whipped out of the water by a big rubber band! <br /><br />Some of the areas we go require that we carry 12-15 gallons of fuel to make the trip, so a person gets pretty creative with the whole placement and weight distribution thing to keep things running reasonably and the handling under control...<br /><br /> I should also mention that in the picture that was taken at speed, that I had just started into a turn, and that the boat usually runs on the back 1/3-1/2 of the hull when travelling straight, which makes a huge difference to the top speed and handling at higher speeds.<br /><br /> THE SHORT VERSION:<br /><br /> Find the lightest motor with the highest horsepower, install Smart tabs, and then tweak and fiddle with it until you get everything out of it that you can......<br /><br /> Cheers,<br /> Snow.

 

[TOHATSU GURU]

Re: Small OB for Inflatable

You do carry a lot of fuel....We have a hard time getting people to carry a three gallon tank. The vast majority of our inflatable customers only use them for ship to shore or island hopping(5 miles or less). And I could not agree with you more.

 

[bcripps]

Re: Small OB for Inflatable

Thanks everyone. This is great information and I’m honestly a little overwhelmed by the response.<br /><br />Looking at the Tohatsu, it seems it is a four stroke and way over the weight restriction for the Achilles. And I don’t see an eTec outboard in the size range so a standard Evinrude/Johnson seems an appropriate choice, particularly when you consider the weight, the fact there is a dealer located in Nassau and the on-line resources regarding repair.<br /><br />The Achilles is the SPD Series with, what I consider, a very stiff reinforced wooden floor and large diameter tubes. I’m not concerned with the boat flexing at speed as long as the boat is properly inflated.<br /><br />The information regarding suitable props is much appreciated and I will investigate the Smart Tabs. They sound like a great idea and one I hadn’t thought of. These teamed up with a five-gallon bow tank should go a long way toward a stable ride.<br /><br />Once again, thank you everyone. This has been a real help.<br /><br />Bryan