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Old 07-03-2015, 11:23   #1
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9.8, 15 or 20 HP

We are contemplating buying another dinghy 10' light weight & would like to plane with 4 people aboard. Which engine do we need or are we asking to much?
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Old 07-03-2015, 11:32   #2
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Re: 9.8, 15 or 20 HP

The correct answer may be whatever is the maximum hp rated for your dingy by the manufacturer. Too much hp, too much weight, and too much throttle may flip your dingy.
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Old 07-03-2015, 11:47   #3
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Re: 9.8, 15 or 20 HP

I have an 10.5' rib and 15 hp, can scare the s#+% out of you...15 is the same weight as most 10's. A 20 hp is to much.


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Old 07-03-2015, 12:25   #4
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Re: 9.8, 15 or 20 HP

Once you have the maximum recommended horsepower for your dingy, this Sport Marine Technologies may help you plane. I have the 200 model.

My 10'6" dingy with a Tohatsu 9.8, and just me in it will plane in one boat (dingy) length.
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Old 07-03-2015, 12:42   #5
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Re: 9.8, 15 or 20 HP

Really depends on the size of the people. If you have 4 people, 2 men and 2 women and they are all reasonably slender a 15hp and 9.6 RIB will plane, no problem. If you American size the people you will need a 10.5 ft dink and 20 HP and you "should" be able to plane.
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Old 07-03-2015, 12:43   #6
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Re: 9.8, 15 or 20 HP

Well, if by four people you mean 800 or more lbs, it takes all of my 20 HP to get on plane with a 3.1 RIB with 800+ lbs of people and a fuel tank etc.
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Old 07-03-2015, 12:49   #7
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Re: 9.8, 15 or 20 HP

Quote:
Originally Posted by Greggegner View Post
15 is the same weight as most 10's. A 20 hp is to much.
This is true for 2-strokes because the 9.9 and 15hp are based on the same engine, while the 20hp is a different one. For 4-strokes, the 15 and 20hp are based on the same engine and weigh the same - the 9.9hp is a different engine.

If you are getting a 2-stroke, get the 15hp. If a 4-stroke, get the 20hp. You don't have to run full-throttle, but it is great to have the reserve.

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Old 07-03-2015, 12:50   #8
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Re: 9.8, 15 or 20 HP

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Originally Posted by robert sailor View Post
Really depends on the size of the people. If you have 4 people, 2 men and 2 women and they are all reasonably slender a 15hp and 9.6 RIB will plane, no problem. If you American size the people you will need a 10.5 ft dink and 20 HP and you "should" be able to plane.
"American size" You are a funny guy. We are all like the people in the movie Wall-E here in the states.
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Old 07-03-2015, 13:25   #9
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Re: 9.8, 15 or 20 HP

Brands vary. Some 15's are the same as the 10's.


The Tohatsu 18 is the same as the 15. The 9.8 is a smaller and lighter motor. Our 18 can plane with 4 (full size) people in a 3.5 RIB, but it takes a little while to get there. I doubt a 15 would do it.
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Old 08-03-2015, 05:38   #10
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Re: 9.8, 15 or 20 HP

Greetings and welcome aboard the CF, Emerson White.
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Old 08-03-2015, 14:48   #11
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Re: 9.8, 15 or 20 HP

Also depends on the dingy design and sea conditions. Sometimes boat shows do demonstrations. Try before you buy is the only way to be certain the combo will do what you want. Also depends on how you will handle the dingy on-board, for 20hp you are going to need a crane I would think.
PS nationality does make a difference, average size of both North Americans and Austrailians is 10-20% bigger than Europeans and even more for Asians. That is regardless of issues about being overweight. I am average height in UK and feel like a midget in Canada, they are all built like hockey forwards!
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Old 08-03-2015, 17:02   #12
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Re: 9.8, 15 or 20 HP

My 10' RIB has a max motor of 15 hp. I went to buy a 15 hp, but ended up buying an 8 hp. The 15 was only a couple of hundred more than the 8 hp, but the salesman talked me down to the 8 hp.

Two reasons:

1) If you drink and ride in the dingy alone, good chance you'll flip it. The 8 hp is idiot proof, won't flip the dink! I have a lot of inexperienced guests drink and drive the dink.

2) My 8 hp Yamaha is roughly 30 lbs lighter than the 15 hp. If you remove the engine from the dink to make a transit often, you're dealing with less weight.
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Old 08-03-2015, 17:27   #13
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Re: 9.8, 15 or 20 HP

Just a thought, why do we need to plane a fully loaded dingy. I agree that being able to do 10-15kn one up for a quick trip to shore is nice but cruising is supposed to be about kicking back, slowing down and getting out of the race. Does it matter if you chug at 4-5kn when collecting the monthly shop or a boat full of guests? Lower power unit is cheaper, lighter and less fuel.
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Old 08-03-2015, 17:39   #14
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Re: 9.8, 15 or 20 HP

Anchored out behind Dog Island in the Panhandle of FL, it's probably more than 5 miles into town to shop and go out to eat, then on the way back being able to jump on plane and do 20 kts to beat the approaching thunderstorm = priceless
Plus just because I can do 20 kts, doesn't mean I have to, and at putt putt speeds , the big motor is almost silent.

Just depends on what you want, many people wouldn't have a motor, nothing is simplier, quiter, lighter and cheaper than rowing, but I'm not rowing 5 miles


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Old 08-03-2015, 18:07   #15
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Re: 9.8, 15 or 20 HP

A64pilot, how long will you be at dog island?

I'm near PC slowly heading that way.

Sorry for OT question.
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