Please share with me the differences between a 4 stroke motor and a 2 stroke in the 150-200 hp outboard range. Issues such as fuel economy, overall maintenance, cost, reliability, etc. would be appreciated. Thanks.
Differences between 2 stroke and 4 stroke motors
- Thread starter jdsmith
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Depends on what type of 2 stroke you are talking about. I have had oler model 2 strokes that smoke and kick and gulp down fuel. I have also had the Yamaha 200HP HPDI and that was / is a great motor - it runs smooth, starts instantly is fairly qiiet conpared to the old ones and is very very dependable with very little maintenace needed, The HPDI is very responsive and get you out of the hole quick. You do need to add oil to the gas.
The 4 strokes are exceptionally quiet especially trolling or idling. I have seen people walk away from their boat on the dock with them running. They are powerful but they do not have that lightning out of the hole speed. I would say my 4 storkes are slightly better in fuel consumption than the HPDI.
4 strokes do not need oil added but they do need an oil change after 100 hours or for most people twice a year. They are still writing the history on these engines - some commercial guys state they have thousands of hours and they are still running flawlessly!
The 4 strokes are exceptionally quiet especially trolling or idling. I have seen people walk away from their boat on the dock with them running. They are powerful but they do not have that lightning out of the hole speed. I would say my 4 storkes are slightly better in fuel consumption than the HPDI.
4 strokes do not need oil added but they do need an oil change after 100 hours or for most people twice a year. They are still writing the history on these engines - some commercial guys state they have thousands of hours and they are still running flawlessly!
wahoo33417
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I'll render some thoughts, but I suspect you can search for many write-ups from professionals.
Two-strokes are simpler engines with fewer moving parts so they weigh less than four strokes. They are a bit simpler to maintain as you add oil to a reservoir rather than change the oil. Because the spark plug fires on every up-stroke of the piston of a two-stroke - as opposed to every other up-stroke on a four-stroke, they generate power more quickly.
But having all the moving parts like valves lifters and cams allows a four stroke to more efficiently move air and fuel into the combustion chamber and then get the burned exhaust gasses out with little mixing with the new, incoming fuel and air. So four-strokes generally put out less emissions. And firing on every other up-stroke means a four stroke generally is quieter and has less vibration.
Another advantage of a four-stroke is it can adapt its timing to various rpms. Most two-strokes target a specific rpm range in which to be most efficient, usually around 4000 rpm. At their most efficient rpm, two-strokes may be just as efficient as a comparable four-stroke. But outside of that narrow range, a four-stroke can adjust the opening of valves and timing of the spark to overcome some inefficiencies.
Life expectancy is generally greater on a four-stroke. Typically, the four-stroke will come with a longer manufacturers warranty. I think this tells you that four-strokes are generally more reliable.
What has become clear is that on coastal or offshore used boats, two-stroke engines are not in demand and are considerably harder to sell.
None of this is set in stone. And for every point I have made, someone could find an example to the contrary.
Hope this helps.
Two-strokes are simpler engines with fewer moving parts so they weigh less than four strokes. They are a bit simpler to maintain as you add oil to a reservoir rather than change the oil. Because the spark plug fires on every up-stroke of the piston of a two-stroke - as opposed to every other up-stroke on a four-stroke, they generate power more quickly.
But having all the moving parts like valves lifters and cams allows a four stroke to more efficiently move air and fuel into the combustion chamber and then get the burned exhaust gasses out with little mixing with the new, incoming fuel and air. So four-strokes generally put out less emissions. And firing on every other up-stroke means a four stroke generally is quieter and has less vibration.
Another advantage of a four-stroke is it can adapt its timing to various rpms. Most two-strokes target a specific rpm range in which to be most efficient, usually around 4000 rpm. At their most efficient rpm, two-strokes may be just as efficient as a comparable four-stroke. But outside of that narrow range, a four-stroke can adjust the opening of valves and timing of the spark to overcome some inefficiencies.
Life expectancy is generally greater on a four-stroke. Typically, the four-stroke will come with a longer manufacturers warranty. I think this tells you that four-strokes are generally more reliable.
What has become clear is that on coastal or offshore used boats, two-stroke engines are not in demand and are considerably harder to sell.
None of this is set in stone. And for every point I have made, someone could find an example to the contrary.
Hope this helps.
Wahoo......excellent piece of writing. I've never seen it put more clearly and to the point. Should be copied and dragged out next time we have the discussion.
The 2 stroke engine came first and the 4 stroke engine came afterwards.the 4 stroke is engine is far more superior as it is more efficient.thats why 2 stroke engines have been banned from production.(due to emission laws).The 2 strokes are lean and cool. The 4 strokes are super duty, almost as lean, do not look as cool but still very cool. But the 4 strokes are much much smoother and make better power.The Titan 4 stroke which is a 48.8 cc 4 stroke will run circles around the F80 2 stroke kits. But the 2 stroke kits are much cheaper. They are both a blast.I consider the 2 stroke Good times motors to be chevys. and the 4 strokes Titans to be caddies. Just depends on what you want and what you can afford.You can also get Caddie 2 strokes. Franco Morini Motori or KTM 2 strokes. These 2 strokes are of super quality and is reflected in the cost at around 500 bucks or more per pop just for the motor. These 2 strokes will run circles around any 4 stroke of comparable size. They make so much power it may tear your bike in half. Keep that in mind.
They still make 2 strokes (HPDI, ETEC, Optimax).
2 strokes weigh less, have more low end power, DI 2 strokes will have similar economy at cruise (but at idle they use at least twice as much and carb models will add about 10%), a little less maintenace costs (no timing belt or valves to adjust but when you factor that over 1000 hours it's not that bad), and reliability is a whole paragraph of it's own. For a lifespan, a 2 stroke can go 2000 hours and a 4 stroke, well, more. Now at 100 hours a year usage that's 20 years, I wouldn't trust either at the age.
The less things there are to go wrong, the more reliable it is. The old 2 stroke carburated motors are very simple, take care of them and feed them gas and they'll run. But on a cold morning they're a PIA to get going.
If you're looking at a used boat with old 2 strokes they will run, run and run but are thirsty (gas and oil) and smoke (which may piss off the Admiral) but treat the boat as hull value only. The years and hours are getting up there. DI 2 strokes are more efficient, start easily but still smoke a little. 4 strokes will have the best overall mileage and don't smoke but loose a little punch. The current boat market is tanked. People treat 4 strokes with 500 hours as being "over the hill" so bid accordingly.
If you want to get a new motor and the hull can handle the weight and 225 HP, my first choice would be the new Yamaha 4 stroke. At the 150 HP level the F150, and at 200 HP it's a toss up between 2 and 4 strokes (any manufacturer).
At resale you're going to take a bath no matter which route you take.
2 strokes weigh less, have more low end power, DI 2 strokes will have similar economy at cruise (but at idle they use at least twice as much and carb models will add about 10%), a little less maintenace costs (no timing belt or valves to adjust but when you factor that over 1000 hours it's not that bad), and reliability is a whole paragraph of it's own. For a lifespan, a 2 stroke can go 2000 hours and a 4 stroke, well, more. Now at 100 hours a year usage that's 20 years, I wouldn't trust either at the age.
The less things there are to go wrong, the more reliable it is. The old 2 stroke carburated motors are very simple, take care of them and feed them gas and they'll run. But on a cold morning they're a PIA to get going.
If you're looking at a used boat with old 2 strokes they will run, run and run but are thirsty (gas and oil) and smoke (which may piss off the Admiral) but treat the boat as hull value only. The years and hours are getting up there. DI 2 strokes are more efficient, start easily but still smoke a little. 4 strokes will have the best overall mileage and don't smoke but loose a little punch. The current boat market is tanked. People treat 4 strokes with 500 hours as being "over the hill" so bid accordingly.
If you want to get a new motor and the hull can handle the weight and 225 HP, my first choice would be the new Yamaha 4 stroke. At the 150 HP level the F150, and at 200 HP it's a toss up between 2 and 4 strokes (any manufacturer).
At resale you're going to take a bath no matter which route you take.
Here's something to consider.
When I bought a 200hp 2-stroke OX66 3 years ago, the price was $6K less than the same hp 4-stroke or HPDI.
The fuel economy savings of a 4-stroke over my 2-stroke EFI are approximately 33%. That means each season, when I spend about $1000 in fuel, I could save $330/year in fuel.
$6000 price difference divided by $330 annual savings = 18 years to recoup extra $.
Sure, you buy oil for the 2-stroke, but you have to pay more for 4-stroke service, so that's probably a wash.
So whatever you do, don't be fooled into thinking you're gonna be saving big bucks by getting a 4-S.
When I bought a 200hp 2-stroke OX66 3 years ago, the price was $6K less than the same hp 4-stroke or HPDI.
The fuel economy savings of a 4-stroke over my 2-stroke EFI are approximately 33%. That means each season, when I spend about $1000 in fuel, I could save $330/year in fuel.
$6000 price difference divided by $330 annual savings = 18 years to recoup extra $.
Sure, you buy oil for the 2-stroke, but you have to pay more for 4-stroke service, so that's probably a wash.
So whatever you do, don't be fooled into thinking you're gonna be saving big bucks by getting a 4-S.