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.
@@tonyfleurys I don't know much about them I just got mine 1981 model. I just built a motor stand for it. The motor looks like it's in good shape,but I haven't cranked it yet. I have to change all fluids,spark plugs don't look bad.
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.
Same reason that the GT-R R34 and several other high performance Japanese cars came from the factory with "223" HP (I forget the actual value), there was a gentleman's agreement between the government and manufacturers that engines couldn't have more than X horsepower.
Believe it or not Michigan recently updated the moped law to allow for up to 100cc, and they allow all kinds of loopholes. It's allowed me to register a 2004 Motorhispania RX50 which has gears and goes 65mph as well as a Suzuki 100cc Enduro.
In the UK even for 50cc and under requires you to be 16, training (£200 for 2 years), insurance at least (£500/year), tax (£20/year) and inspection (£30/year). Only then can you ride around in the rain at 28mph
@@kennethnoisewater1502 That's booty, Move to Michigan if you want completely legal cannabis and much relaxed road rules over the UK-also red light cameras are illegal and you're not under surveillance virtually everywhere you drive.
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! 🙂
You used to only need a boating license for motors 10 and above in Ontario, Canada. Now it’s for all motors but you still need to register any boat with a motor 10 or above. It seems like 10 has always been a sort of a cutoff internationally for various reasons.
@@TACOINSURANCE True. There are several rules regarding age, licenses and so on, and engine power is often used as a "divider". But many of these rules are newer, most boating used to be quiet unregulated, and the HP tax (ca 1970 - ca 2015) was the main cause for all those "9.9".
The Johnson and Evinrude 9.9 was indeed as you describe when I was a lad in Australia. You could also buy the 15. Before that there was the Johnson 9 1/2. A more full rounder engine housing.
It takes more than minutes. You can change the carb and reeds, but if you’re not changing the exhaust ports, as well, then it won’t actually be a 15hp. You can get a little more power by changing the carb, but the exhaust ports are the greater point of restriction. I have a 1963 evinride 10hp, and it’s the same engine from 4hp all the way to 40hp. The only difference is the carb and exhaust ports.
😂 actually the mnr have been known to actually take the vin# number and with a app they have can verify hp directly from the vin# and yes they do sometimes make the effort to check!
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.
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.
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.
Jay Dee your wrong, Evinrude never made a 9.5 hp motor; It was 9.9hp. I worked for Evinrude for 17 years. I started in 1974, my father worked there for 34 years, my FIL worked there 32 years. The last 18 years he assembled 9.9hp and 15hp powerheads. The one difference being the carburetor and reed plate under it. By replacing them your 9.9 becomes 15 hp. My older brother assembled the starters, reed plates and other parts for the 9.9, 15, 25, 33, 35 hp lines. Just so you know very many OMC Brand (Evinrude, Johnson, Gale) outboard parts are interchangeable; some are not. When my Grandfathers 1961 15hp Gale outboard finally quit running, my father and I simply put a new 25 hp Evinrude powerhead on the Gale lower unit. They did make a 7.5 hp for a while in the late 60’s to early 70’s, my Uncle Frank owed one.
@@kypackerfan4-12-15I know Johnson made a 9.5 with a low profile power head I believe designed to fit in trunks of cars better. Alot of brands made an outboard just under 10hp so people could use them on waters with horsepower restrictions usually a 10, 20 or 25hp limitation hence 9.5,9.8,9.9,18 variations of popular brands. The 28 33 48 65 75 88 and other unusual horsepower variations usually signified some extra option like a charging system oil injection electric shift or some other definable difference. Evinrude history is quite extensive. The more ive learn the less i think i know.
The evinrude 9.5hp was also called the toilet bowl motor Johnson in the early 60s had a 10hp I like the 9.9 with the 15 hp carb i actually built up a evinrude with a out of the water exhaust and went directly to the bypass cover and put a small dirt bike tuned muffler I did have to drill out the jets and play around with it and it only ran good when it was cool out in the spring and fall ?
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…
This is why! A licence or registration is mandatory for all pleasure craft equipped with motors of 10 horsepower (7.5 kilowatts) or more, including personal watercraft, which are principally maintained or operated in Canada.
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.
Was going to comment the same - - they also tend to make 2 "ratings" for a "casting" size, I had a Johnson 18 that looked identical to a Johnson 25 (1973) A marine tech told me I could get it up to 23 HP with parts but I'd have to open the engine up to get the last 2 HP. I never modded it as I had an 11' fiberglass boat and it was already over-powered.
Here in Alaska there is a river that they limit HP to 35. Many of these motors are just detuned 40-50HP motors. Some guys even fix what limits this but keep the 35HP cowling.
Here in Europe the cc limit for mopeds are up to and including 50cc. My understanding is that manufacturers make them 48 or 49 cc so that at least one cylinder bore is possible without making the moped into a motorcycle in a legal sense.
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. 👍
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!
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.
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!
Haha- I remember the exact same thing,having to duck as my dad attempted to start our old Seagull 4 hp outboard with the cord wrapped around the flywheel- often many times ,as it was incredibly unreliable!🤣🤣👌 great memories…..
There are many older 2-cycle 9.9 outboards out there that can be had on the cheap that are still in great operating condition. And many others that can be easily repaired at little expense. Just make sure the lower unit and power head are in good operating condition (repairing those will run into money and are best handled by someone with some expertise). The other repairs on these outboards can be easily done by the average do-it-yourselfer and for minimal cost. You can find many of the parts you need on ebay on the cheap, with lots of vids online on how to do the repair. I love my little1985 Johnson 9.9! Still runs like a top, pushes my little 14 footer with ease and starts up on the first pull. And it allows me to fish on many bodies of water that have that 10hp restriction.
I just purchased a 20 HP Suzuki from that website you're looking at. Great experience and great service. They will ship any Outboard 30 HP and below directly to your home.
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
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.
I thought it was because there are so many lakes restricted to under 10 horsepower. Therefore it made sense for manufacturers to produce 9.9 horsepower outboards instead of 10.
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.
Keep in mind that the ratings on outboards have a tolerance of plus or minus 19% of the rating. So a 9.9 motor could be about 11 hp or only 9hp and still be legal. Think of ICOMMIA and NMMA as industry agents that regulate how the motors are rated. ( I worked in Outboard Engineering for over ten years for OMC.)
i had a johnson 10 and it lasted for many years sold it to a friend who used it for years after. it was a great motor . anything good is always discontinued.
@@OldManMuskrat it’s a 14’ alumacraft from the 70s so very light, I’d guess 250 ish lbs so quite a bit less than yours. I’d suggest going with the max rated hp as noted on the capacity plate
I purchased a Mercury 6hp 2021 model 4 stroke and it’s the best purchase I’ve made. I don’t like to go offshore at all and mostly use my boat on freshwater lakes here in Australia. It’s so cheap to run even at today’s prices and the servicing costs are super low as well. It’s just “fashionable” to have big motors here in Australia but not at all necessary.
I've owned a bunch of boats, but my favorite was a 9.9 Johnson on a quality inflatable with wood floor. That thing would get on plane so fast and would skim along comfortably at about 1000 miles per hour. 😂 Okay, not that fast but at 16 it sure felt like it and was a bit of a sleeper in that its speed surprised everyone I took out. Huge smiles.
There is another reason too. Many states Boating Under the Influence laws have engine qualifications in them. Ours is 20 hp in MS but others are less in surrounding states.
10 hp is the threshold of Mississippi law that one can be cited for BUI. I always had figured some judge with a bourbon habit persuaded the legislature to figure out a way he could take his little runabout on a public lake while day drinking.
Alot of them are actually 15 or even 20 horsepower that have a restrictor plate so the company doesn't have to make more than one motor for a similar sized outboard
Oh, keep it simple way. There was, and probably still is, a huge jump in tariff and taxation for engines 10hp and larger. So the manufacturers come as close as they can (9.9) without hitting ten. Same reason that a Japanese 1.6 liter auto engine is 1.597 liters, never 1.6.
My old 40 hp Johnson was actually a detuned 60. During that model run, the 40, 48, 50 and 60 were essentially the same engine. Same bore and stroke for all four.
What i like about the 9.9s is that it is a small 2 cilinder and dus way quieter than a 2.5-6hp cingel cilinder. And even a little quieter than a big two cilinder. Also got les fibrition.
Herr in Canada if you have a 10 hp or more outboard you have to register your boat and apply your number on the boat usually on the left and right side towards the front.
AZ has a 9.9 hp rule. I came to AZ from Colorado with an almost new i5 hp Yamaha. I do not know what their rule there is now but at that time they had a no-wake law; no limit as to hp. So coming to AZ I was in a quandary about what to do. The owner of a local boat repair shop advised me that the difference between a 15 hp and an 9.9 is the carb and the sticker on the motor. He sold me a 9.9 sticker and all is well.
AND THE JOHNSON 10 I BOUGHT WAS WELL USED WHEN I BOUGHT IT . I USED IT FOR MANY YEARS SOLD IT TO A FRIEND WHO THEN USED IT FOR MANY YEARS AFTER THAT. IT WAS WHITE IT HAD PLENTY ENOUGH POWER TO WATER SKI BEHIND A 14 FT. FIBERGLASS LONE STAR BOAT. I'LL NEVER FORGET THAT LITTLE JOHNSON 10 WHAT A GREAT OUTBOARD MOTOR . NOT TOO BIG OR HEAVY TO CARRY IF NEEDED. NEVER HAD TO HAVE ONE SINGLE REPAIR FOR SOME REASON . TRULY GREAT OUTBOARD MOTOR. MY FIRST SENTENCE EMPHASIZES MY POINT . THE ONE I HAD WAS FROM THE 60S IF YOU EVER HAVE THE CHANCE TO GET ONE , DO IT .
One thing he forgot to mention, is that these 9,9 HP outboards (2-stroke versions) actually all are dowmtrimmed 15 HP engines. In Norway, when 2-strike outboards were prohibited some years ago, you could get good money for a 9,9 HP 2-stroke. And within some minues of work, you had a 15 HP 😁
I‘d agree if the video was called „Why there are no 10HP outboards in the USA and Canada“. There are plenty 10HP outboards available outside those two countries
I have a Johnson 9.9 hp outboard 1994 use on my 26 foot canoe. Maintenance was very low. Switched the prop to a stainless steel and had it refurbished for 80.00$. Reasons for the purchase are exactly what was said in the video clip. I don’t think Johnson manufacture the 2 cycle outboard as many have gone to 4 stroke.
Most of the lakes in NJ where I live limit you to "UNDER" 10 HP. If they allow powered boats at all. So, 9.9 it is. But you can get engine covers labeled 9.9 for 15 HP motors which are essentially the same.
As said by others most of the 9.9 2 stroke outboards are derated 15 HP units. This is also the case with the other HP ratings as well until you get to the really big stuff. it stands to reason you are not going to make radically different motors just to get 5 HP more. All the 9.9 units I owned just required the fuel jets in the carburetor to be upgraded to the 15 HP spec and a limiting screw on the ignition advance removed then the motor would also have increased RPM that gave more HP and speed.
In the 60s thru late 70s Mercury used to take the HP of the engine and add a Zero to it, a 50hp became the Merc 500, a 7.5 was the Merc 75. however the 9.8hp was called the Merc 110.... a crafty way of outright thumbing the nose at the Regulators
Wait I thought I was called at 110 because it’s an 11 cubic inch motor. Correct me if I’m wrong but my 1968 Mercury 110 is clear as day labeled 9.8 HP Twin on the lower cowling.
@@74nova36 You need to reread my comment, and comprehend it. Your logic doesn't hold up very well, cause the inline 6s were 99.8 cubic inches, but they were called 900, 1150, 1250, 1350, 1400, and 1500, respectively 90hp, 115hp, 125 hp, 135hp, 140hp, and 150hp. There were higher HP racing engine of that displacement too.
@@pjimmbojimmbo1990 dang you’re a coot. You can displace the same amount while making different amounts of horsepower per given cubic inch. ✋🏿 All 9.8's used Merc's 10.9 cubic inch block, and throughout it's life the block was never modernized. It was a "headless" split block with the reeds located in a (donut) around the lower portion of the crank - a real pain if you had a reed problem - had to crack the block to get at them. The 9.8 started it's model run in 1962 as the model 110 with Merc's Phelon ignition system. In 1970 it got the first "thunderbolt" ignition system - the "thunderbolt 2 - Phase Maker". In 1974, while still called the Model 110 it got Merc's Thunderbolt 4 ignition which stayed in production as Merc's near perfect ignition until 2005 when most 2 strokes were discontinued. In 1979 it simply became the 9.8. In 1985 both the block (which was shared with the 7.5 horse) and the 9.8 model were discontinued. 1986 saw the launch of the 6/8/9.9 horse models with a new 12.8 cubic inch block (designed and built by Yamaha exclusively for Merc) which combined with the T4 ignition became the best and most reliable 2 stroke portables ever to hit the market. *Be open to being wrong* I am, and still could be wrong
@@melrose9252 thanks for verifying that my original claim was correct. Just got my 1968 9.8hp up and running! It makes a ton of power for 11 cubic inches!!
My state says under 10hp and you don’t need a special boating license. Motors that actually make 15hp are packaged as 9.9 hp for our market here. The state made the 10hp rule but never checked the manufacturers claim. The mercury 2 stroke 9.9 makes about 13 propeller hp
New Yamaha F60 is also sold as the F50. The difference is that Yamaha puts a different ECU on the F50, adds a removable restrictor to the air intake and puts on a smaller prop. In all reality, they do not make a 50hp motor, they just remove the balls from the 60hp motor.
I have a classic 60s 14 foot fiberglass runabout. The boat only weighs about 700 lbs. Will this 10 hp push my little boat up river against current? I'm not looking for speed. 5mp is enough for me.
Years ago rented boats at 4 or 5 different towns in New Jersey. All we're 9.9 HP . was told several explanations from insurance company , no boater training require red with them some kind of age limit ( maybe 14 or 16 ) . The boats for a little faster when they switched from heavy wood to lighter fiberglass. Ran the 9.9 HP in 16 mile wide Delaware bay over 6 hours and never used all of the little red maybe 5 gallon gasoline can .
9.9 hp motors are often down-tuned 15 hp motors. Not always, but often. And most of them can quite easily be converted back to 15 hp just by changing a few parts. 10 hp motors on the other hand, are mostly designed as 10 hp motors from the beginning. Which means that a 9,9 might in fact be larger and heavier than a 10 hp motor. But also with potentially more power. This is very generally speaking, and a lot of exceptions exist.
@@WayneTheBoatGuy Yes, and not only the small motors. I have a 40 hp Yamaha which is basically the same as the 50 hp. And it's the same all the way up to 300 hp. Most outboards are usually released in at least to hp ratings. Quite often three. From a production point of view, it doesn't make sense to design a unique motor for every hp rating.
I always figured it was a tax/licensing thing to see 9.8hp motors abroad. Meanwhile the same motors would be labelled as a 10hp motor here. Because over here the question of whether or not you need a license and registration for a boat is whether or not it can reasonably go over 5 knots. If it's slower than 5 knots, you probably don't need a license unless it's over a certain size or displacement. So you can have a decent size boat with a 25hp motor on it, as long as it doesn't go over 5 knots when using the motor. You can go faster when sailing or rowing for example. This can obviously only really be enforced by cops in a boat. And after a couple of court cases they have to measure the speed in two opposing directions, and then use the lower of the two, so they can't shaft you by making you go downwind, downstream, or both.
I have been told that FLORIDA was the first state to put restrictions on the horsepower of motors used on certain lakes and that limit was 10 horsepower creating the first 9.9 horsepower motors This then spread around the world.
Tomos company which produced 2 stroke outboards ranging from 4 to 20HP, also had a 10HP and a 9.9HP variant. Bore and stroke were identical to the 18HP, but there were only 2 channels instead of 3 inside the head - so it wasn't just detuned, but a different block. The 20 was oversized 18 variant, and the company was in process of developing a 40HP when the SFRJ collapsed.
Can you run two motors? Currently the Suzuki 6 HP DF6AS5 is on sale for $1,450 so two will give you 12 HP for $2.900. You will need to link them together somehow but it could work.
You can fly a plane at any age(16 to solo), but you need to be fourteen in FL to operate a boat. It’s a second degree felony to aloe your under age children to operate a boat while your with them. It’s a good thing I didn’t grow up in this day and age.
Truck manufacturers do the same thing, sometimes de-rating the exact same frame and drivetrain GVWR to one pound under the threshold for commercial license requirements.
Jahjan is right Many 2 strokes were upgraded with a reed plate change and carbs. some could get a tuned exhaust. With Old Mercurys it didn't matter as they were under plated and when you bought a 15 hp it was a 20 from the factory, which made many evinrude guys complain they were beat by a 15 merc.
for example i have a suzuki's df9,9brs efi motor and it is the same engine as 15 and 20 the 20hp variant is just restricted whit ecu software and intake restrictor to be 9,9 or 15hp
Why are there so many 9.9 hp boat engines and not 10 hp? As you may have noticed, many manufacturers offer 9.9 hp boat motors instead of 10 hp. There are good reasons for this: Some inland waterways may only be used with an engine under 10 hp. Some countries require boat registration on boats with an outboard motor of more than 10 hp. Manufacturers have specially designed the 9.9 hp outboard motors to meet these requirements.
I haven't owned a boat for a long time but it used to be that you didn't have to register a boat under 9.9 hp so no K numbers had to be painted on the side of the boat.
In Canada, both the boater and the boat have to be licensed, you need a boat training to show the competency to operate a motor over 10 hp and register your boat with Transport Canada.
my first out board mtr. was a 5hp elgin my dad traded for it back then hardly any body had a boat you could rent a wooden boat at the lakes about $1.00 a day bring your small mtr or row we did have cousions and life jackets a can of worms and 2-3 cane poles we were happy back then
You're splitting hairs. Part of the reason they are labelled as 9.9 is because of the confusion people will have when they that a body of water is restricted to 10 hp. Some of those might say "10 hp max" or "lake limited to 10 hp" or "must be under 10 hp" and there are people who would ask, "what if my motor is 10 hp?" When an engine is labeled as just a smidgeon under 10 hp, it makes it more clear because no matter how a sign, regulation, or law is written - 9.9 hp is clearly under 10.
To go a bit further into the explanation of these peculiar decimal differences, a 9.8hp is a 209cc block where a 9.9hp is a 333cc block. The 9.9 is a detuned 20hp motor, basically. There’s a relatively large weight difference between the 9.8 and 9.9- about 15lbs. The question I have is, why would manufacturers make the 9.9 in the larger block at all?
Answer: Manufacturing costs. Easier and cheaper to design one block that can be modified for several different hp limits Usually comes down to slapping a bigger or smaller carb on the block to change the hp. For instance, my 9.9 Johnson can be turned into a 15 hp just by swapping out the 9.9 carb out for a 15 hp version. But then you would be over that magic 10hp limit.
good to know, I've got a Grumman 19 foot flat back and my 7.5 is a little weak when going up narrow river shoots with faster current wanted a bit bigger motor and was thinking 9.9 or 15, but if that 9.8 is lighter that might be a more valuable aspect.
@@melrose9252 see, the 9.8 vs 9.9 was simply a naming/differentiation thing. Tohatsu manufactures motors for mercury up to 30hp and Merc’s 10hp motors (pre 2022 maybe) I believe had the two different blocks as well. I have a Tohatsu 9.8 but am aware of their 9.9 which has the the 15 and 20hp block. The main point I’m making is.. with regards to 4 strokes only, some outboard manus have a 10hp in two forms. And it’s good to know what you’re getting because weight can be a big factor for some.
HP restricted lakes, is the original reason why they was marketed as less than 10 hp. 9.9 is usually 15hp with smaller carb. Makes same low end torque as 15hp, to get boat on plane, hp and speed restricted by rpm and prop choice. Needs the same low end torque as 15hp for pontoon boats to maintain control and propulsion in windy conditions. On old Johnson / Evinrude outboards, 9.9hp engine cover fits 15hp engines.... Smaller engines don't need a title or registration in many states too.
i don't know about any other country but in ontario if your motor is 10 horse or above you have to license the boat. so they call it a 9.9 for this reason. i have fished in ontario for 50 years and was always given this reason. in michigan any boat that has a motor has to be licensed.
really... back in 1973 I got a birthday present of a 10'MFG fiberglass boat with a 9.9 Johnson for around 800$ new. I found out the 9.9 and the 15 had a mechanical difference... the carb, the 15hp motor had a higher fuel flow. By buying a 15 hp carb rebuild kit, all one had to do was change the jets and readjust the air for idle and full throttle. If you shaved the top of the intake port a bit to allow an earlier timing of fresh fuel input and advance the spark about 3 degrees, you would get more hp out of the motor... I ended up with approx 17hp at full throttle. I miss that boat...
10hp and 15hp engines actually have the same body, the only difference is the carburetor which increases the power, so if you have a 10hp engine and you think it is too weak, you can find a carburetor of the same type as 15hp and you have a 15hp engine
