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Old 18-08-2015, 10:35   #16
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Re: what size outboard for dinghy?

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I would say get two outboards: a 3.5HP and a 15HP. The 3.5 at 22lb you will love when you only need to go ashore or to a neighboring boat. No wrestling the heavy tank and motor, it's installed in one minute. But if you need to go a mile or will be staying put for awhile then the 15 will be a blessing.

Bingo. And if you can only carry one then think what is more important. On Chesapeake easily deploying the OB is key so we only have a 3.3 2 stroke which is child's play to put on dinghy. But when we go further we will likely get the standard planing rib with 15 hp. (though may stow the 3.3 in a locker for easy deployment)...


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Old 18-08-2015, 10:39   #17
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Re: what size outboard for dinghy?

The horsepower limit on the plate has to do with safety and what the Coast Guard considers safe for the typical boater. It has nothing to do with weight or the manufacturers warranty. The Coast Guard takes into consideration what the typical weight of an engine with the max horsepower is going to be.

Use common sense and you may be able to exceed the max horsepower by a little.
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Old 18-08-2015, 10:47   #18
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Re: what size outboard for dinghy?

We used a 6hp Tohotsu on our AB rib last season. It did not have enough power to plane. I had the prop pitch lowered and it performed much better., could plane with one person. So if you are just on the edge of performance you might consider having the prop adjusted for $30, worth a try.
In the end we bought a Mercury 2 stroke, 9.9 at 73 lbs so it should do the job. A good used 2 stroke or even a new one from the Bahamas may be a better solution if weight is a concern.
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Old 18-08-2015, 10:54   #19
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Re: what size outboard for dinghy?

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Originally Posted by David M View Post
The horsepower limit on the plate has to do with safety and what the Coast Guard considers safe for the typical boater. It has nothing to do with weight or the manufacturers warranty. The Coast Guard takes into consideration what the typical weight of an engine with the max horsepower is going to be.

Use common sense and you may be able to exceed the max horsepower by a little.

You can exceed it by a lot.

And anyway do you mean the US coast guard? Or what country? As the OP hasnt said where he is cruising.
The US Coast Guard only covers ONE country. Guess where that is?? Anyway, if the USCG has that as a rule please screenshot the reference and post it here.

As Mark, ColeMJ, says the parameters are weight, so if the person purchases a 2 stroke OB (country dependant only on NEW OBs) he will find an 15HP 2 stroke is half the wieght of a 15 HP 4 stroke, or thereabouts.

So can so eone in the USa buy a 2 stroke? Yes! If its second hand and they tell me virtually new ones are sold in US from Canada. Also the Bahamas and everywhere south. So it could be well viable for a new cruiser to buy small in the US for his wander down the ICW and repower in the Bahamas....


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Old 18-08-2015, 10:58   #20
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Re: what size outboard for dinghy?



Then get back to me.
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Old 18-08-2015, 11:00   #21
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Re: what size outboard for dinghy?

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Originally Posted by SaltyTanned View Post
I would say get two outboards: a 3.5HP and a 15HP. The 3.5 at 22lb you will love when you only need to go ashore or to a neighboring boat. No wrestling the heavy tank and motor, it's installed in one minute. But if you need to go a mile or will be staying put for awhile then the 15 will be a blessing.
A great suggestion he has the 6, which probably is light weight. He just needs the 15.
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Old 18-08-2015, 11:07   #22
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Re: what size outboard for dinghy?

We have a 10' AB aluminum RIB and an 8 HP Yamaha 2-stroke. It planes just fine with me alone, will barely plane (after a while and with lots if noise) with me and my spouse, IF we don't have much stuff along with us. But it is only 65 lbs, which matters a lot to us. Our friends have 15 HP engines, and always give us 5 minutes head start when we are heading out to a dive site together. But they weigh at least 93 lbs, and that's a real pain for us. We have a motor lifting hoist on our boat, but there are always the times when you need to schlep the motor when away from the mother ship.

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Old 18-08-2015, 11:13   #23
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Re: what size outboard for dinghy?

Just use the google custom search function for 'dinghy outboard size' and you will see half a dozen earlier threads on the same topic.
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Old 18-08-2015, 11:55   #24
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Re: what size outboard for dinghy?

There are lightweight four strokes now, My 20 HP Suzuki is 99 lbs.
I rarely remove the motor from the dinghy, if you have good davits anytime it's safe to leave the dinghy on them, it's safe to have the motor too, (in my opinion), good davits should easily hold 250lbs or so easily, it's very likely if you have a motor on a dinghy, one davit is carrying way more than half the weight. (There are times you should not have a dinghy hanging from davits, (again in my opinion)

Small boat HP ratings are honestly pretty arbitrary, but I guess you have to have something, right? (again my opinion) you may can safely exceed rated HP, or maybe not even safely reach rated HP as it's just simply formula based, not on how a boat actually handles the HP.
http://www.boats.com/outboard-horsep...r-steer-boats/
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Old 18-08-2015, 11:56   #25
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Re: what size outboard for dinghy?

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Any thoughts on the viability of sailing with the outboard still mounted on the dinghy? Do I need to stick it on the rail every time I haul it up? Does that happen before or after I haul it up or is this like everything else sailboat and it varies from boat to boat?
Well, without having a clue as to the size or type of boat you sail, or the how substantial your davits may be, etc... My first thought would be:

Don't even THINK about it...

;-)
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Old 18-08-2015, 12:04   #26
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Re: what size outboard for dinghy?

We own the same Avon as the OP. Our 15 hp Mercury 2 stroke won't get up and plane with more than 400 pounds of humans onboard, so unless you're inviting four little people onto your Avon, forget about planing. And we have one of the power booster prop surrounds with the metal wings to assist attached to the outboard.

And..... We just pulled out one of the davit lifting attachment points on the dinghy stern earlier today. What a hassle trying to fix split and cracked old dinghy fiberglass. Still trying to figure out a suitable repair.
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Old 18-08-2015, 12:09   #27
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Re: what size outboard for dinghy?

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You can exceed it by a lot.

And anyway do you mean the US coast guard? Or what country? As the OP hasnt said where he is cruising.
The US Coast Guard only covers ONE country. Guess where that is?? Anyway, if the USCG has that as a rule please screenshot the reference and post it here.

As Mark, ColeMJ, says the parameters are weight, so if the person purchases a 2 stroke OB (country dependant only on NEW OBs) he will find an 15HP 2 stroke is half the wieght of a 15 HP 4 stroke, or thereabouts.

So can so eone in the USa buy a 2 stroke? Yes! If its second hand and they tell me virtually new ones are sold in US from Canada. Also the Bahamas and everywhere south. So it could be well viable for a new cruiser to buy small in the US for his wander down the ICW and repower in the Bahamas....


Mark
No Mark, where does the USCG cover?

You Aussies obviously have a different idea of what is a safe power to weight ratio. (See post 20 and Google Aussie 18's) Ok, yeah, I am guilty of wanting a 427 Shelby Cobra replica when I retire.
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Old 18-08-2015, 12:09   #28
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Re: what size outboard for dinghy?

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Why is that? The dinghy is not in warranty. Those HP ratings have more to do with controlling engine weight than HP. Since the 15 and 20 weigh the same, no reason not to go with a 20, even if the plate says 15 - one needn't use the entire throttle range if things get squirrely...

Mark
Think about the forces the engine puts on the transom when trying to lift that 1000+ pounds out of the water. Maybe some users are careful to never open it full up but I have seen a handful that give it whatever there is.

Some ribs have very strong transoms, others less so, etc.

b.
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Old 18-08-2015, 12:13   #29
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Re: what size outboard for dinghy?

Pretty sure the engine ratings have to do with CG regs. Same for the weight ratings. If you exceed the plate limits on either you are probably opening the door for a rookie/trainee to ticket you (in the US).
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Old 18-08-2015, 12:30   #30
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Re: what size outboard for dinghy?

Yup, we do the same - and it works really well for us. We havea 2.6m dinghy for the kids that has a Yam 3.5 Malta & a Yam 15 Enduro. For the main 3.4m dinghy we have a Yam 5 and a Yam 25 Enduro. All great engines. Just be careful using too big a motor. Both our dinghies are both rated to 30hp
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