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Comment by ajross | Hacker News Reader

What this article is really saying is "Two stroke engines are outrageously nasty". Which we knew. They really are dozens of times worse for immediate pollutants (soot/particulates, hydrocarbons, NOx) than a routine car engine and catalytic converter. And they're significantly less efficient, so even their CO2 output is quite a bit higher than a gas engine of the same power.

But they're a tiny market and no one has bothered to try to regulate it. This just isn't a big thing from a save-the-planet perspective. But it's a nifty product.

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This is not 2-stroke. This is 4-stroke engines. There are no catalytic converters on marine outboard motors, so the 4-strokes are allowed to be > 100X as polluting as cars.

It's a 25-40HP outboard. I don't have numbers, but the bulk of completing conventional engines in that range are going to be two strokes. They aren't selling big motors yet.

Most 25-40 HP outboards sold today are 4-stroke. The only significant brand that's still 2-stroke in the US is Evinrude, and it has < 10% market share.

I think it is illegal to sell >= 25HP two stroke boat engines in Europe. When we last bought one they only had four strokes.

Out in open water it doesn’t matter as much as in front of your kids school.

Try swimming anywhere near a gas-powered boat and you'll instantly taste and smell how gross it is.

Is 2 stroke really that common for personal-use boats? I've only heard of them running on 93 gas, which is all I see sold at marinas, no oil to mix in.

I've seen tiny outriggers used for fishing,etc that are two-stroke. Maybe some jet skis too? I'm not sure.

Certainly anything substantial won't be two-stroke.

As I understand it, there are increasing restrictions and calls to ban 2-stroke marine engines for smaller lakes, because the exhaust contains a fair amount of oil mist that settles on the water.

If nothing else, the noise is a nuisance on small lakes. I grew up next to a small community-governed lake on which all gas was banned. People have been using electric on that lake for ages, which is particularly feasible since it's a small lake (300 acres or so iirc). Electric for small stuff makes a ton of sense and has for a long time.

My parents-in-law also live by a lake where all ICE's are banned. Mostly people row, and a few have electric outboards.

It's really wonderfully quiet, even though it's close to a city.

Besides the oil, the carbureted 2-strokes emit 25%+ of their fuel unburned.

A long time I read about some "next generation" 2-stroke thing, where they had fuel injected directly into the cylinders, after the piston had already blocked the exhaust port. The intake port was only used for air. A bit like those behemoth 2-stroke marine diesel engines.

Evidently it didn't really work out well enough, considering most outboards they sell these days are 4-stroke. I've always had a soft spot for 2-stroke engines, seems so wasteful to "waste" half of the strokes on a 4-stroke. Oh well.

Evinrude's E-Tec line is two-stroke and goes up to 150 horsepower in the G1 series, and to 300 horsepower in the recent G2. That's pretty substantial.

OTOH, they have done a lot of engineering to meet emissions requirements, so they are a far cry from grandpa's old outboard that left trails of blue smoke.

The E-Tecs have done exactly what you said - a lot of engineering to meet emissions requirements. Unfortunately, the requirements for outboards include CO, NOx, and HC, but not P2.5 or P10 (particulate) emissions, because they are much simpler and less scrutinized than the regulations on cars (which DO have particulate limits). The E-Tecs put out 30X as much particulate emissions as the 4-strokes.

It depends. My family bought a boat, and it came with a 90HP outboard engine that was 4 stroke. For they same price, they offered a 2 stroke engine that was 120HP. Everyone agreed adding a single bottle of oil when you fill up the tank with gas was a simple enough thing to do to get the extra 30HP. My family also never filled up at the marina because of the extreme mark up. The boat was always on a trailer, so it just got filled up on the way at any normal gas station.

I’d damn near take that 90 over the 2 stroke. The father in law just got one on his McLay boat and it’s quiet with none of that 2 stroke smell. I’ve lost count of the number of times we’ve been idling out at sea idling and asked each other “is that thing still running?”

Wow. That makes me consider upgrading. I feel guilty just staring at or hearing my (2 stroke) motor idling!

With 2 stroke you need to mix the oil with the fuel before injecting it into the engine in order to lubricate all the moving parts. With 4 stroke the oil and gas are kept separate and you just feed the fuel in.

4 stroke is more commonly sold today but with boating, the lifespan of the equipment is so long that there are a non-trivial amount of 2 stroke engines still in use today.

True, and they're so bad that CARB published a report saying one long day in a 2-stroke jetski pollutes as much as 10 years in a typical car.

Many small boats have an oil injection system that injects 2 stroke oil from a tank into the fuel as it's consumed (so that you can fill the fuel tank with pure gas and the boat manages the injection/mixing).

I grew up in the 80s & 90s running a 150HP 2-stroke Mercury outboard. Fed it oil on each fill-up. Amazing sounding engine, but in hindsight, horribly polluting.

With that outboard at wide-open-throttle, you were emitting ~ 4 gallons of unburned gasoline per hour out the exhaust, not to mention the oil you cited.

My understanding is that things are a little more complex than they appear. Take a look at the Tohatsu offerings [1]

They offer both 4 stroke and "TLDI" versions of many of their outboards. The TLDI is a two stroke but with updated tech that meets pollution standards and the oil is not mixed with the gas before hand, the oil is mixed with the gas in real time from it's own separate tank with in the motor.

Tohatsu is pretty careful not to mention "two stroke" on their site because of its bad connotations from the past.

[1]https://www.tohatsu.com/outboards/all.html

There are 15.7 million recreational power boats in the US alone (1 for every 10 households), 70% of those in the installed base are powered by outboard motors. This is not the car market, but it is not tiny.

While it's not a small market, it's in the Bay Area's blind spot. Fishing is the 2nd most popular outdoor activity in the US, behind running. In the US, there are 20 million people who fish for freshwater bass alone (1 in 16 Americans). Bass Pro Shops is the Missouri unicorn that grew from nothing to be big enough to buy Cabela's for $5 billion, based largely on their boat sales.

If you have numbers about how often these recreational boats are used I'd be interested

There are all sorts of surveys, but the best source I've found for real data on how much these boats are used is this official report on fuel usage (2013):

https://www.fhwa.dot.gov/policyinformation/pubs/pl17012.pdf

Basically, it indicates that recreational boats use 1% of the fuel of all passenger cars.

In terms of pollution you also have to consider that these boats are being used a lot less than cars. However, another thing to consider is that some of the diesel, petrol, and oil inevitably ends up in the water.

In terms of maintenance and cost, I think it is interesting that battery electric is becoming competitive here. It wouldn't surprise me if some countries start putting rules in place to ban dirty engines from some sensitive areas. Apparently the EU already has a lot of rules around boat engines already that are complicated and hard to enforce and not that effective yet. But like the car industry, boat engines are subject to emission standards, inspections, certifications, etc. and the rules are getting stricter.

I imagine that once battery electric becomes cheap/common enough, a lot of boat owners will choose to go electric rather than buying a cleaner engine just to ensure they stay on the safe/legal side with their boats and avoid fines. Also, doing the right thing when you are actively enjoying nature is probably going to motivate a few people.

Many types of pollution are also less impactful over the middle of the ocean. Acid rain and smog for example simply get diluted into nothingness under the ocean.

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