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Old 16-03-2018, 08:15   #1
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Dinghy Motor Size

Howdy all,
I just ordered my new AB, 9'6 Aluminum dinghy with floor and bow locker. We will be leaving So Cal next year for Mexico and South America and..... Question is my thought is to go with the Yamaha 15 hp 4 stroke (since I cannot but a 2 in the US). Is 15 hp overkill, too much motor, just right or should I save the weight and couple hundred dollars and go with the 9.9.

My gut suggests I will be glad to have the added power and speed but the motor is approx. 20 lbs more.

Thanks for your suggestions.
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Old 16-03-2018, 08:26   #2
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Re: Dinghy Motor Size

I've gone through two successions of having a dinghy with 9.8HP and upgrading to a 15HP outboard. The difference is like night and day, particularly as I anchor out all the time and sometimes have long distances to go (e.g. between the Dutch and French sides of St. Martin).

If you can afford it then go for the 15HP. But.... the 4-Stroke is significantly heavier than the corresponding 2-Stroke model. So if you can wait until you get to Mexico and points south then I'd opt for a 2-Stroke there. I currently have the Yamaha 18HP and can lift it out of the dinghy and onto the boat and vice versa - but only barely. Any heavier and I'd need to build a hoist, particularly in rough or choppy weather.

I won't go back to a 9.8 a third time
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Old 16-03-2018, 09:10   #3
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Re: Dinghy Motor Size

Iím with the ďless is moreĒ group. Iíve had fast dinghies and enjoyed them, but have enjoyed my slower, low powered dinghies more. My dinghy speed is about the same as my sailing speed. The perks; lower purchase cost, lower operating cost, less weight (really nice when loading/unloading from mother ship) and less fuel to transport. I donít cruise to rush around.
My 2 cents
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Old 16-03-2018, 13:17   #4
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Re: Dinghy Motor Size

If you go the 15hp route, get something cheap and small now, and buy a 15 2 stroke when you get out of the US.

I did, and sold the 3.3 merc a week after getting the 15 yamie. I love it.

Another thought is a buddy has the new version of the tohatsu 4-stroke which is really light. Not sure what the specs are but you might check on those if going 4stroke route.
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Old 16-03-2018, 13:57   #5
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Re: Dinghy Motor Size

All good information ergo the quandary. I hear good things about the Yamaha 15 even the 4 stroke and only $230 more than the 9.9. I still have a year and a half left before I set south so I do need a good motor until then.
Thanks
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Old 16-03-2018, 14:30   #6
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Re: Dinghy Motor Size

I'm kind of in this quandary now, as well. I recently picked up a Zodiac 340 air-floor. The whole boat only weighs 90 lbs but is rated for 15 hp! I've got an ancient 3 hp, and an ancient 18 hp. Currently rebuilding the 18. Seems like something in between might be more optimal. Although the power might be nice when headed out a few miles to a dive site with a couple of bodies and a couple of scuba rigs. But it might be nice to have something built in this century.
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Old 16-03-2018, 14:42   #7
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Re: Dinghy Motor Size

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Originally Posted by Captain Randy View Post
All good information ergo the quandary. I hear good things about the Yamaha 15 even the 4 stroke and only $230 more than the 9.9. I still have a year and a half left before I set south so I do need a good motor until then.
Thanks
Take a look at the Suzuki 15. It has fuel injection and will not have any trouble from ethanol gas while you're still in the states and at 98 lbs it's nearly 20 lbs lighter than the Yamaha. I bought one almost four years ago with no regrets. My Yamaha 15 had no end of carb problems. The passages in the small carbs are easily clogged and hard to clean. Suzuki's are getting pretty popular outside of the US so service is not too hard to find, not that I've needed any.
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Old 16-03-2018, 14:53   #8
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Re: Dinghy Motor Size

I had a Yam 15 on a 10+ ft rib and a 9+ ft rib. It was a bit much for the 9 footer, power wise. The 9 was a bit out of control!. Are 9.9 vs 15 different weights now? I like the idea of buying a 2 stroke in Mexico. DO you have a small motor to use in between?
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Old 16-03-2018, 15:50   #9
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Re: Dinghy Motor Size

Yes the 9.9 weighs 20lbs less than the 15 Yamaha. I will also look into the Suzuki. Would love more feedback from the group on the Suzuki as that make a whole lot of sense.

Thanks
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Old 16-03-2018, 16:24   #10
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Re: Dinghy Motor Size

If your not going too far almost any motor will get the job done but if your contemplating world wide travel, especially off the beaten track I would own a Yamaha 2 stroke and the 15 is a great choice, fairly light and bullet proof, anyone can fix them and you'll get parts almost anywhere in the world plus they have great resale value...there is a downside...If there were 10 dinks on the beach, each with a different motor you'd be better off with some other brand because the locals will steal a Yammi way ahead of anything else.
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Old 16-03-2018, 16:52   #11
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Re: Dinghy Motor Size

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Yes the 9.9 weighs 20lbs less than the 15 Yamaha. I will also look into the Suzuki. Would love more feedback from the group on the Suzuki as that make a whole lot of sense.

Thanks
With the weight savings I would think it would be fine on the 9 ft dink. I had a Suzuki 200 HP four stroke and it was a great engine.
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Old 16-03-2018, 18:54   #12
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Re: Dinghy Motor Size

Quote:
Originally Posted by Captain Randy View Post
I just ordered my new AB, 9'6 Aluminum dinghy with floor and bow locker. We will be leaving So Cal next year for Mexico and South America and.....
Congratulations

Quote:
Question is my thought is to go with the Yamaha 15 hp 4 stroke (since I cannot but a 2 in the US). Is 15 hp overkill, too much motor, just right or should I save the weight and couple hundred dollars and go with the 9.9.

My gut suggests I will be glad to have the added power and speed but the motor is approx. 20 lbs more.
I do not have a RIB but I have been following the discussions closely and doing my research.

Regarding HP, much depends on the load in the boat. With two people, you should be fine with a 9.9. With four and a load of groceries, you'll still get there but will have difficulty getting up on plane. I don't think 15 hp is excessive but the motors are heavier.

2 vs. 4 stroke

I grew up in the two stroke era and have lived through the transition to four strokes.

Yes, you can get 2 strokes in Mexico. I personally would not want one. Here's why.

- You will go through twice as much fuel as you will with a four-stroke of the same size. The real problem with this is one of fuel handling. With a modern 4 stroke you can go as far on a 3 gallon tank as with a 2 stroke on a 6 gallon tank. Fuel weighs 6 pounds a gallon, so there's weight, and then there's the handling.

- You will have to mix gas because the small two-strokes now being sold outside the U.S. aren't set up with oil injectors. If you have done this, you know how it goes; if not... well, you have to carry the correct oil with you, you have to go through the mixing steps whenever you refuel, if you have other equipment that requires straight gas (generator, other outboard) you have to keep track which is which.

- Two strokes generally have more trouble with plugs fouling, especially at idle, which is particularly a problem if trolling, less so for typical dinghy use cases

- There will be a slight oil slick in the water around you. How do you feel about that?

- The unburned hydrocarbons will produce a certain "outboard aroma." It will get on your clothes. Perhaps it will become part of your mystique.

- While there is some weight savings, it is not as great as it once was when 4 strokes were first introduced. There are no true 15 HP motors in 4 stroke -- the 15 and 20 Tohatsu 4 strokes come it at 94.7 pounds vs. the Yamaha 2 stroke 9.9 and 15 hp which are both 83 pounds.

The choice is yours
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Old 17-03-2018, 00:32   #13
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Re: Dinghy Motor Size

A quick post as I am rushing to work...

I have the exact same AB with floor and locker and the new 9.9 Yamaha 4-stroke. For 2 adults it works perfectly but add a 3rd person and it wonít plane anymore. So depending or your situation you might want to get the 15hp.

Having said that both the RIB and the Yamaha are absolutely brilliant. Couldnít be happier with them!
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Old 17-03-2018, 01:35   #14
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Re: Dinghy Motor Size

Unlike Jammer, I've had 5 RIBS in the past with 4 Tohatsu 9.8HP 2-Strokes and one Tohatsu 15HP and one Yamaha 18HP 2-Stroke (same engine block as the 15HP)


Quote:
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You will go through twice as much fuel as you will with a four-stroke of the same size.
I'm not sure about using double as much fuel, but the consumption is higher. I use the RIB several times daily, and fill up the fuel tank every 3 weeks or so.
Quote:
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You will have to mix gas because the small two-strokes now being sold outside the U.S. aren't set up with oil injectors.
True. It takes all of 10 seconds and that is done while filling up the fuel tank. And if I forget the oil, the fuel dock will have it.
Quote:
Originally Posted by Jammer View Post
Two strokes generally have more trouble with plugs fouling
RIBS are usually run WOT, so fouling doesn't happen
Quote:
Originally Posted by Jammer View Post
There will be a slight oil slick in the water around you.
If the oil is mixed correctly there is no visible oil slick. Ever. Partly due to the exhaust being routed underwater to the propellor area and helping hide any evidence.
Quote:
Originally Posted by Jammer View Post
The unburned hydrocarbons will produce a certain "outboard aroma."
This aroma is overpowered by the scent of diesel aboard Seriously, the outboard is downwind of you so you and your clothing aren't going to be getting any unburned hydrocarbons (plus as mentioned above, the exhaust gets routed underwater behind you)

Now to add my comments in favor of 2 strokes:

- No complicated electronics which will fail. Usually when far away from spare parts access.
- I've had 2 engines "go swimming" and application of clean fresh water rinse, WD-40, taking the carburetor apart and cleaning it did the trick each time. 2-3 hours work and the engines ran again.
- Going up and down the Caribbean island chain I've seen many other cruisers. The overwhelming majority have 2-strokes for their outboard. Those with 4-strokes tend to be recent arrivals from the U.S. or Europe where new outboards need to be 4-strokes.
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Old 17-03-2018, 03:23   #15
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Re: Dinghy Motor Size

The hardest tradeoff is weight. If you have a motor crane and don't find it necessary to manhandle the outboard, then the 15 is a good size for a 10' dink. I personally like the Suzuki, which is almost as light as a two stroke and has an excellent reputation. But still too heavy to manhandle around. 15hp in a RIB of that size will usually plane with 3 people and groceries, and with less than full throttle. Versatile if you have distances to cover.

I don't have a motor crane and due to how I use the dinghy, need to be able to carry it, so I could not go that big. I ended up with a Selva 8HP four stroke. Very light (27kg) because it is a one-cylinder, unlike most outboards that size.

I am generally pleased with it, although it is just on the edge of what one person can carry and handle, and it is not powerful enough to plane the dinghy with people and gear (two people and no gear it will plane, but needs more or less full throttle). That doesn't bother me too much because I just don't use the dinghy much for long distances.

Only you can figure out the right tradeoff. Weight in the davits is another question in case you carry the dink in davits.

As to two versus four stroke -- that's another one you'll have to answer for yourself. I love two strokes for their simplicity and lightness. I have not experienced any plug fouling or starting problems with two strokes whatsoever since all of them went to electronic ignition. With a two stroke, you don't have to change oil or filter, and you don't have to worry about setting the motor down wrong and the oil running out. But I have experienced far better fuel economy with four strokes, which is a real boon in remote places.
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