If you've been scouring local classifieds or hanging around the docks lately, you've probably noticed that the 9.9 nissan boat motor still commands a lot of respect among boaters. It's one of those engines that just seems to refuse to quit, even though Nissan officially exited the marine engine market in the U.S. years ago. You'll see these little workhorses strapped to the back of everything from aluminum fishing boats to sailboats acting as kickers, and they usually have a layer of salt spray and a lot of stories to tell.
The thing about the 9.9 hp class is that it's the "sweet spot" for many boaters. It's powerful enough to get a small hull on a plane, yet light enough that you don't need a crane and a team of three people to mount it on the transom. When you add the Nissan nameplate into that mix, you're talking about a piece of machinery with a bit of a cult following. But if you're looking at buying one today, there are a few things you should probably know before you hand over your cash.
The Secret Identity of Nissan Outboards
One of the first things people realize when they start digging into the history of the 9.9 nissan boat motor is that it wasn't actually made by Nissan. At least, not in the way you might think. Nissan Marine engines were actually manufactured by Tohatsu. For decades, Tohatsu built the engines, and Nissan simply rebranded them with their own decals and paint schemes.
This is actually the best news possible for anyone owning or looking to buy one. Why? Because Tohatsu is one of the most reliable outboard manufacturers in the world, and they're still very much in business. This means that if you pick up an old Nissan 9.9, you aren't stuck with an "orphan" engine. Almost every part on a Nissan 9.9 is identical to the parts on a Tohatsu 9.9 of the same era. You can still walk into a marine supply shop or jump online and find carb kits, impellers, and spark plugs without breaking a sweat.
Two-Stroke vs. Four-Stroke: Which One Are You Looking At?
Depending on how old the motor is, you're either looking at a classic two-stroke or a newer four-stroke model. Both have their fans, but they offer very different experiences on the water.
The Lightweight Two-Stroke Legend
The older two-stroke 9.9 nissan boat motor is a favorite for guys who have to lug their engine from the truck to the boat every weekend. These things are incredibly light—often weighing in at under 80 pounds. They are punchy, they sound like a classic outboard should, and they have very few moving parts to go wrong.
The downside, of course, is that you have to mix your gas and oil, and they aren't exactly "green." They smoke a bit at idle and they can be a little noisy. But in terms of pure power-to-weight ratio, it's hard to beat an old Nissan two-stroke.
The Reliable Four-Stroke
As environmental regulations got tighter, the four-stroke 9.9 nissan boat motor became the standard. These are much quieter and more fuel-efficient. You don't have to worry about mixing oil, and they idle beautifully, making them perfect for trolling.
The trade-off is weight. A four-stroke is beefier and can be a bit of a back-breaker if you're trying to move it solo. However, if the motor is going to stay on the transom all season, the four-stroke is usually the way to go for the sheer convenience and smoothness.
Why the 9.9hp Rating Matters So Much
You might wonder why everyone is so obsessed with the 9.9 number specifically. It seems like a weirdly specific decimal, doesn't it? Well, it all comes down to regulations. Many lakes and reservoirs across the country have a "10 horsepower limit."
By labeling these engines as 9.9, manufacturers allowed boaters to get the maximum allowable power without breaking the rules. Interestingly, many 9.9 nissan boat motor models were actually "detuned" 15 hp engines. In some cases, with just a minor tweak to the carburetor or the throttle linkage, you could essentially turn that 9.9 into a 15, though I didn't tell you that.
What to Look for When Buying a Used One
If you find a 9.9 nissan boat motor for sale on a site like Facebook Marketplace or Craigslist, don't just take the seller's word that it "runs great." These engines are tough, but they aren't invincible.
Check the "Tell-Tale"
When you start the motor, the first thing you should look for is a solid stream of water shooting out the back (the tell-tale). If it's just a dribble or nothing at all, the water pump impeller is likely shot. It's a cheap part, but if the previous owner ran it like that, they might have overheated the engine, which leads to much bigger problems like a warped head or a blown head gasket.
Look at the Oil (For Four-Strokes)
If it's a four-stroke, pull the dipstick. If the oil looks like chocolate milk, walk away. That's a sign that water is getting into the oil, usually through a failed seal or a cracked block. You want to see clean, amber-colored oil.
The "Cold Start" Test
Always ask the seller not to start the engine before you arrive. You want to see how it starts when it's cold. A healthy 9.9 nissan boat motor should pop to life within a few pulls (or a quick turn of the key if it's an electric start model) even when it's chilly. If they have to spray starting fluid into the carb to get it going, you're looking at a carburetor cleaning job at the very least.
Maintenance: Keeping the Dream Alive
The reason so many of these motors are still around is that they're incredibly easy to work on. You don't need a computer to diagnose a Nissan 9.9. Most of the time, if the motor isn't running right, it's one of three things: fuel, spark, or air.
The most common issue by far is a gummed-up carburetor. Modern ethanol gas is brutal on small engines. If you let a 9.9 nissan boat motor sit for three months with ethanol gas in the float bowl, it's probably going to struggle to start. My best advice? Always use ethanol-free gas if you can find it, and always run the engine dry (disconnect the fuel line and let it stall out) if you aren't going to use it for more than a week.
Changing the gear luster oil is another "must-do" every season. It takes ten minutes and costs about ten bucks, but it prevents your lower unit from seizing up. Just look for the two screws on the lower unit, drain the old stuff, and pump in the new stuff until it oozes out the top hole.
Is It Better Than a New Mercury or Yamaha?
That's the million-dollar question. If you buy a brand-new 9.9 from a big-name brand today, you're getting a warranty and the latest tech. But you're also dropping a few thousand dollars.
A used 9.9 nissan boat motor in good condition might cost you a third of that price. Because they were built by Tohatsu—who also built engines for Mercury for a long time—the quality is essentially the same. You aren't "settling" for an inferior brand; you're just buying a version of a world-class engine that happens to have a different sticker on the side.
Final Thoughts
At the end of the day, the 9.9 nissan boat motor is a bit of a hidden gem in the used market. It doesn't always have the brand recognition of a Yamaha or a Honda among casual boaters, but those in the know realize exactly what it is: a bulletproof Tohatsu in disguise.
Whether you're looking for a reliable kicker for your sailboat or a main power plant for a 12-foot tin boat, these motors are hard to beat. They're simple, they're rugged, and as long as you keep the carb clean and the water pump fresh, they'll probably outlast the boat you put them on. Just make sure you do your homework, check the compression, and maybe bring a friend who knows their way around a wrench when you go to check one out. Happy boating!