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post #1 of 44 Old 11-28-2018 Thread Starter
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Dinghy outboard size

Guys and Gals,

I just bought myself an inflatable from West Marine for Christmas. Now for the hard part. Talking my lovely bride into a new motor. The boat is a PSB-275 Performance Segmented Floor Inflatable Sport Boat; 9' long, 90 pounds. What size motor can I get away with? The thing is my Mrs. is tall and slim but not much muscle. I would like a 2.5 HP (ish) for that reason. We are not yahoos, so whipping around the bay at break-neck speeds is not a problem. Anybody out there using a small motor for their inflatable?

Thanks,

Don
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post #2 of 44 Old 11-28-2018
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Re: Dinghy outboard size

I chartered a boat that came with a 2.5 hp. I can't remember the exact size of the dinghy, but it was something like what you've got.

I thought it was fine. We didn't plane, but we got around fine. We didn't do any long distances though, just around a mooring field and to a dinghy dock. (It was the Lehr 2.5 hp propane, to tie this into another thread going on...)

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post #3 of 44 Old 11-28-2018
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Re: Dinghy outboard size

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Originally Posted by DonScribner View Post
Guys and Gals,

I just bought myself an inflatable from West Marine for Christmas. Now for the hard part. Talking my lovely bride into a new motor. The boat is a PSB-275 Performance Segmented Floor Inflatable Sport Boat; 9' long, 90 pounds. What size motor can I get away with? The thing is my Mrs. is tall and slim but not much muscle. I would like a 2.5 HP (ish) for that reason. We are not yahoos, so whipping around the bay at break-neck speeds is not a problem. Anybody out there using a small motor for their inflatable?

Thanks,

Don
I use a 2.3 for some pretty solid cruising on my 21 foot sailboat. All day every day, through canals, into currents, into big winds, into 2-3 foot waves, all 4 at once.

Definitely it is fine. Lots of people will tell you you need charging, you need reverse, you need an engine that will make popcorn, but a 2.5 is fine.
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Re: Dinghy outboard size

I have a high-pressure bottom 10' from WM.

I started out with a Mercury 6 and with just myself could sometimes plane if perfect conditions.

I have also bought a Yamaha 2.5 with an internal tank. I took out 4 adults and two children and we did fine.

The Yamaha is much lighter, less trouble with an internal tank and starts much easier.

The Mercury never was an easy start even brand new.
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post #5 of 44 Old 11-29-2018
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Re: Dinghy outboard size

I use a 2hp Yamaha 2-stroke on my 7.5 foot Achilles. Not enough to get on a plane, but plenty for short to medium length trips. I LOVE the light weight (22 lbs).

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post #6 of 44 Old 11-29-2018
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Re: Dinghy outboard size

According to one of the reviews although the boat is rated for 10hp the floor buckles too much at speeds over 4 mph making it only appropriate for a 2hp engine.

If your not going to be regularly loading it to its max 1,103 lbs capacity a 2 to 2.5hp motor should be just fine for puttering around the marina/mooring.

https://www.westmarine.com/buy/west-...boat--17981184
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Re: Dinghy outboard size

There is a ton of personal preference here and a bit of what each needs their dinghy to do. Most dinghies are overpowered for just shuttling to shore, inside a flat water, protected, no wake, speed limited anchorage. If that's all you'll ever do, don't over think it.

On the other hand, I think many/most will eventually find the desire to get out and explore a bit and being on plane can be a great advantage. Some anchorages are more remote that others too. In some cases, being able to plane can make anchorage choices more flexible, as being further out, in a safer less crowded places becomes more practical. I clearly see most boats going to great lengths to squeeze in as close to shore as possible. I don't want to have to do that.

Weight is always a consideration. I had a center console dinghy, with a 20 hp motor, that required the davit line be run around a winch to haul her up. I hated that. My current dinghy is an aluminum RIB with a 9.9hp (personally, I'm not a fan of inflatable or inserted floors). It's well more than we need to shuttle even a dinghy full of 6 people to shore. With just two of us, we can get up on plane, unless we are dead into a tough wind and chop. The combination of the lighter aluminum dinghy and motor are easily hoisted by hand.

However, we do find ourselves wanting a bit more get up and go, from time to time. It's not frequent enough for me to regret the 9.9, but next time around, I bet I go for the larger HP (still on the lighter hull) to have more options. It would only add about 20 lbs, so hoisting shouldn't be notable different.
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post #8 of 44 Old 11-29-2018
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Re: Dinghy outboard size

I have been using inflatables (not RIBs: I don't like RIBs) since 1972 and if there's one thing I've learned is that having a too small motor on an inflatable has some rather uncomfortable drawbacks. We have a 3hp for emergencies and unbelievably it burns about 3 times more fuel than our 15. Of course, we are running the 3 at full throttle and the 15 at about half, but still....
First and foremost is getting wet whenever the weather is a bit blustery. If you don't have the hp to bring the bow up you are going to get sopped in even a mild chop.
You may not wish to be "whipping around the bay at break-neck speeds", but when it is raining cats and dogs and you are returning to the boat with a load of groceries, a 5-minute trip would be a lot better than a 20 minute one. Sure, you could wait out the rain and come back another day, or sit in the bar for hours instead of being cozily onboard in dry clothes.
Then there are your guests to consider. If a 2.5 gets you around OK with 2 aboard, what will happen with 4?
So, my suggestion is that you get at least a 5 hp engine, though an 8 (at very nearly the same weight) may be a better choice. You can always go slow (and much more economically) with a bigger engine, but you can never go faster with a little one.
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post #9 of 44 Old 11-29-2018
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Re: Dinghy outboard size

Be mindful that the OP has a less than 100 lb wooden accordion slat floor 9 foot PVC Dinghy from West Marine so I would take the "High Performance" part of the advertisement propaganda with a grain of salt. These tend to get a bit skittish when you over power them. PVC does not usually hold up that well left out in the sun either and the transom mount is prone to coming unglued so its prudent on those to go with the least amount of outboard practical for your needs. We just threw some similar store brand PVC inflatables in the dumpster that were new (never been used still in the box) because they all came unglued due to the storage unit where they were kept being too warm. All past warranty too. We will glue triangular gussets in front of and behind the transoms of new PVC inflatables if the max sized outboard that its rated for is going to be used.


OP is in Maine so just keep it out of direct sun on hot sunny days when your not using it and go with the smallest outboard that fits your needs.

Last edited by SeaStar58; 11-29-2018 at 09:11 AM.
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Re: Dinghy outboard size

No correct answer here. Every depends on where you sail, how you sail, how often you anchor and how many people are on board... plus the size of the mother ship if stowing is a consideration.

I've own many dinks over the years... hypalon and PVC. From my perspective/and use PVC is fine. I've had wood removable floors and several aluum RIBS. I've had OBs from 2HP to 8HP, 2 and 4 stroke.

For passage you can't tow so you need to stow... that becomes a consideration. We tow "locally" and use a demoutable lifting crane to get the 95# 4 stroke 8 HP OB onto the rail. Very easy and can be done by one person.

As I prefer to anchor out as opposed in close in for multiple reasons... I need a dry dink (large tubes) and an OB that can get us there quickly when need be (rain).

Our RIB tows very nicely... but yes it does slow the boat a bit. Keep the bottom clean as it makes a big difference towing or motoring the dink.

My last 2 stroke 6 was fine... I decided to change to 4 stroke because I didn't want to deal with oil.

For most applications you can get by with a 4HP or even 2... But they do not work with external tanks and range is limited.

Dink is VERY important when cruising. You will use it multiple times each day... and so is the OB. For us larger does not make sense... we are usually just 2 and we can do 4 with no sweat. We find 10' works for us. Without the lifting crane a heavy OB is a non starter. We never ever tow the dink w/ OB on.

Our choices may not work for you.

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Last edited by SanderO; 11-29-2018 at 01:26 PM.
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