Why There Are No 10 HP Outboard Motors

Why are there no 10 hp outboard motors? There are no 10 horsepower small outboards because of some specific state laws and rules. If you want a little 10 hp outboard boat motor the closest options are buying a 9.9 hp outboard motor or a 9.8 hp outboard engine. There are reasons why you can not buy a new small 10 hp outboard engine for your boat and those reasons are quite odd and unusual. A 10 horsepower boat motor hasn't been made for many decades!

In this video I discuss how we often hear about ten horsepower outboard motors but in reality, they don't actually exist. We are forced to buy a 9.9 Mercury outboard motor, or a 9.9 Suzuki outboard engine but none of the brands offer a 10 hp version. Yamaha, Tohatsu, Honda, Suzuki, Mercury and even back when Johnson and Evinrude were still outboard brands - you couldn't get a 10 hp version of their outboard motors. Find out why in this video!

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00:00 Introduction
02:48 Why we can not buy 10 hp outboard engines in the USA
05:05 Are 9.9 horsepower outboard engines more expensive than they were 40 years ago?

#smalloutboards #10hpoutboard #9.9hp

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Photo by Roland Chanson on Pexels
Video of boat at sunset by Ahmet Kurt on Pexels
Sound effects and additional music is copyright free from iMovie

[WayneTheBoatGuy]

Several people have commented that Honda still makes a 10 hp, and from the overwhelming number of comments, I believe it to be true. However, in the USA (where I am located) the Honda website only shows a 9.9 and no 10 hp. Obviously, the 9.9 and a 10 are the same engine and it seems that outside of North America it is still labeled as a 10 hp. I apologise for my "blanket statement" that there are no 10 hp outboards because it seems like this phenomenon is primarily a US and Canada thing. Also I do realize that "once upon a time" there were 10 hp outboards in the US and Canada - but it seems that era ended in the 1970s - around 50 years ago. So to those of you who insist on telling me that Johnson or Mercury made one in the 1960s, - I know they did. This video is addressing the several reasons WHY our 10 hp outboard motors are currently (and have been for the last 50 years or so) labeled as 9.8 and 9.9.

[em]

The answer to why something is an odd number is always "the government". 49cc mopeds and minibikes exist for the same reason. 50cc and greater require licensing and registration.

[janhanchenmichelsen]

Outboards under 10 HP used to be exempt from the old HP-tax here in Norway. Back then, the shops sold 9, 9 HP. These simple two-stroke motors could be retuned to 15 HP in minutes. If you needed some parts, the shops sold ready packed, cheap "service kits" for 15 HP. Even if there were no 15 HP engines for sale in the whole country! 🙂

[simonilett]

I worked for a Mercury/Mariner dealer here in Australia back in the mid 90's.
Our sale price on a 9.9hp two stroke outboard was $990AU and a 15hp was $1500AU.
The prices went up pretty much the same way as HP increased, so it was pretty straight forward when it came to estimating prices for a customer.
Also, as others have mentioned, a fair few manufacturers 9.9hp engines were basically a restricted/tuned down 15hp engine.
Effectively all that is needed to upgrade a 9.9hp to 15hp is to fit a 15hp carburetor and 15hp exhaust tube to the mid section, although installing the 15hp exhaust tube does require lifting the powerhead/engine off the mid section to install.

[dale]

I had a 15hp mercy and found out that a merc 6hp hood fit the 15hp. All good.

[larryh]

In many cases, the 9.9 hp motors are 15 hp motors detuned to meet the requirements you mentioned. What's interesting is many of the 9.8 hp motors are 8 hp motors tuned to make slightly more hp. On a small boat, a 9.8 would make more sense as it's lighter, thus easier to lug around.

[jaydee]

This actually goes back decades. An uncle of mine had a late 60s vintage 9.8 Mercury. My grandfather had a 9.5 Evinrude Sportwin from around the same era. An interesting, extremely low profile powerhead. As to vintage outboard costs, I still have a 1975 model 20hp Mercury that we bought new for $775.

[nixxonnor]

Many 9.9 HP outboard motors are actually 20 HP motors that have been purposely limited in performance to either 15 or 9.9 HP. I think this is the case for some Suzuki, Tohatsu, Mercury and Yamaha outboards. If you swap out the limiting part(s), you regain the designed HP of the outboard.

[danpolo]

They do the same with 49 cc mopeds and scooters. That one cc makes it so that you don’t need a motorcycle license to use it here in Florida.

[jeremiahbrumble]

I have several 10 horse power motors!! They are all 1950s and 1960s Johnson and Evinrude they run great!

[motorvN]

Thanks for this informative video. These were the reasons I had always suspected for the not-quite-10hp-motor…
There are some similar shenanigans at the upper end of the two digit range. For instance, Yamaha used to make a 100 hp motor. More recently, like in the last 10 to 15 years, they began making 90 hp motors instead, one of which sits on the back of my boat. A Yamaha tech told me while I was looking at used boats that the 90 hp motors are simply rebadged 100 hp motors because the insurance industry had started increasing rates significantly for engines above 100 hp. So Yamaha obliged and started “building” engines that were 10 hp less…

[killfloor]

I love my 1956 Johnson 10 HP. I found it in someone's garbage. Converted it into a single line with a pulse carb, threw in and impeller and it runs like new. Pushes my 12' just fine

[alandaters]

Different motors are "perfect" for different boats. Back in the day when my Dad got a 1.7 HP Neptune Mighty Mite, it was a huge improvement over either of us using oars to propel a 10-12 ft wooden boat with 2 people on board! The best part is that it would outrun the mosquitoes and other bugs on the sunset run on Peconic Lake back to the dock in August. Maintanance was easy, they thoughtfully built it with great access to everything. The only issue- the front passenger better duck during starting, the knot on the end of that non-recoil starter rope could really hurt!

[andrewdouglas]

I had a Tohatsu 9.8 Hp that was nearly fifty years old and still ran perfectly. I only ever changed the spark plugs and the transmission oil. It started first time every time. What a great motor. 👍

[_onesimpleidea]

Took a long long time to say a little little bit, but it _was_ interesting. Don't pay too much attention to the "that's technically inaccurate if measured with a micrometer" crowd. Just keep doing your thing!

[hjc]

Anyone remember the GREEN 10 HP Mercury from many years back? It was rumored to be close to 20HP. We all used them on our little Hydros.

[NotAMartian-]

In Canada a pleasure craft with a motor under 10hp you don’t need to license or register your boat. So a 9.9 is a beautiful thing here.

[artfisher]

I had a 10 HP motor as a kid in the early 70’s. A 1958 Johnson. Anybody else old enough to remember the maroon and white Johnson’s? Had it on a 12ft boat and it flew. Noticed they changed to 9-1/2’s in the 60’s.

[alanploetz]

It's fun finding stuff like this, even if I'm coming to it a year later.
I didn't know about the registration issue, but experienced both the age limit and motor size on certain bodies of water.
In the 60s I started with a mid-50s 7.5hp Evinrude on a very heavy 16' cedar strip fishing boat. When I was 12 I took the Water Patrol's Boating Safety course so I could operate our family runabout with 60hp without a parent along.
Later, when I finally got an aluminum 12ft fishing boat, I got a 9.8hp Merc. Of course by then I was dreaming of the Evinrude/Johnson low profile 15 horse.
I remember when MSRP for small outboards was about $100/horsepower and larger engines came in well under that.
Oh, the memories.

[rdunbar]

Suzuki's 9.9 and 15 hp are the same except 2 parts. The 9.9 has a restrictor air plate that lets in less air. And the ECU module is different, A lot of people drill out the plate to a larger hole and swap the ECU and presto you have a cloaked 15 hp motor.