4 stroke vs 2 stroke

[RFSims]

DFI is on it's way out. Most auto designs are going to EFI and DFI but that will not last.

Most modern engines are hydraulic and the few auto engines that are not usually have an adjustment interval over 2khrs.

I'm sorry but this does not answer my question. I asked specifically about the new Mercury 4 stroke 3.4 and 4.8L engines.

I do know that Yamaha uses screw/lock valve adjusters and Suzuki uses shim/bucket in some of their engines. Since Yamaha made some models of Mercury 4 stroke outboards I would think that the have screw/lock adjusters. I have seen where Mercury recommends a valve check every 100 hours or 1 year. I would be very surprised if any model/make of 4 stroke outboard uses hydraulic vale lash adjusters.

[BassinR83]

4s>2s

[leo13]

Good point. I looked closely at a cut away of the V8 and it uses bucket style lifters. It is speculation but there are 24 and 32 valves which is a lot to have to keep track of so one would assume they are hydraulic or have a long service interval. The maintenance schedule sticker says nothing about valve adjustments at 100 or 300hrs. The older small four strokes were manufactured by Yamaha before the Mercury/Yamaha law suit. Now they are manufactured by Tohatsu.

I'm sorry but this does not answer my question. I asked specifically about the new Mercury 4 stroke 3.4 and 4.8L engines.

I do know that Yamaha uses screw/lock valve adjusters and Suzuki uses shim/bucket in some of their engines. Since Yamaha made some models of Mercury 4 stroke outboards I would think that the have screw/lock adjusters. I have seen where Mercury recommends a valve check every 100 hours or 1 year. I would be very surprised if any model/make of 4 stroke outboard uses hydraulic vale lash adjusters.

[EuropeanAM]

Don't know if they are going to use the term "maintenance free" but they are about as close to that as you will get.

Long-through bolt design blocks, combined with top-quality valve train components have proven to require very little maintenance as the clearances do not migrate like they do in traditional short-bolt design systems.

This started back with the first Verado... and has proven that the design works well. Obviously a V-series block is going to be slightly different, though similar results/theory can be applied.

[cintaskevin]

I'm sorry but this does not answer my question. I asked specifically about the new Mercury 4 stroke 3.4 and 4.8L engines.

I do know that Yamaha uses screw/lock valve adjusters and Suzuki uses shim/bucket in some of their engines. Since Yamaha made some models of Mercury 4 stroke outboards I would think that the have screw/lock adjusters. I have seen where Mercury recommends a valve check every 100 hours or 1 year. I would be very surprised if any model/make of 4 stroke outboard uses hydraulic vale lash adjusters.

No Valve adjustments on the new Mercury fourstroke product.

[Jetboy]

There is always a market for a good engine. As long as mercury supports the 2 cycles they will be fine.
4 cycle is the future or even present. But some can’t afford to buy the new stuff. There is nothing to be hating on the 2cycles for they have hung in for a long time and still preforme well on a cost basis. There is a reason murcury waited this long to make the move.
4 cycles have been here for years.

I hope the new engines do well. Hammer sure had its issues to start.
‘Go team black’

[22R]

First, I like both but prefer a 2 stroke for a lot of things.

I always get a kick out of the four stroke guys going to the "We have to compare HP to HP..." which immediately negates the advantage the 2 stroke has of a power stroke every revolution.
Then they point to how the weight has decreased and power improved on the 4 strokes BY DEVELOPMENT AND TECHNOLOGY, which HAS NOT BEEN DONE to the same extent to the 2 strokes.
And lastly "2 strokes wear out faster". Well duh. Twice as many power strokes. When do you think the most wear occurs? ON THE POWER STROKE!

Everything got geared for four strokes and most manufacturers do not see a reason to switch development over to two strokes. There are always some that will buck the system. KTM of motorcycle fame is one of them. The new 2 strokes (motorcycles) don't have the narrow power band of years past and are clean burning. Tons of bottom end torque. Same with the winter sports folks. Lot's of two strokes there. I won't get into big trucks as weight is not a factor there and they are diesel.

Remember the saying, "4 strokes have one cycle for power and one for wearing out". Lot's more parts to wear out, generally more expensive to repair, and STILL generally heavier. When the tech catches up on the 2 strokes, and it will, then this discussion will change again.

Good Post !! and valid points.
The new 4 stroke is impressive as I have said but imagine how light and powerful they could have made a 2 cycle if they had wanted to. I wish BRP much success in keeping them alive.

22R

[FastCat04]

Above post says 'imagine how light and powerful they could have made a 2-stroke if they had wanted to''. I think the answer is obvious....due to EPA regulations a V6 250 2-stroke weighs exactly the same as a V8 4-stroke !! So, when asking 'imagine what a V8 2-stroke would weigh...the answer would be 'a lot more than a V8 4-stroke' !!! It's actually the fuel delivery system that drives the 2-stroke weight up. Air compressor being the single biggest component....but add fuel rails, plumbing, VST and so on....and it's easy to understand why 4-strokes now weigh less per cubic inch than 2-strokes.

[22R]

So technology could not have advanced to lighten the fuel delivery system as well ? How does KTM do it with motorcycles ?
Not saying you are wrong just wondering.

22R

[leo13]

That is incorrect. Much of the same technology used to reduced the weight of the newest 4 stroke designs can be used to reduce the weight of a 2 cycle. Might I remind you that the V8 has nearly 250 more components then the 3L it replaces. The G2 does not use an air pump, it is not currently nescasary. I'm not knocking the new design just stating the facts.

Above post says 'imagine how light and powerful they could have made a 2-stroke if they had wanted to''. I think the answer is obvious....due to EPA regulations a V6 250 2-stroke weighs exactly the same as a V8 4-stroke !! So, when asking 'imagine what a V8 2-stroke would weigh...the answer would be 'a lot more than a V8 4-stroke' !!! It's actually the fuel delivery system that drives the 2-stroke weight up. Air compressor being the single biggest component....but add fuel rails, plumbing, VST and so on....and it's easy to understand why 4-strokes now weigh less per cubic inch than 2-strokes.

[2500]

That is incorrect. Much of the same technology used to reduced the weight of the newest 4 stroke designs can be used to reduce the weight of a 2 cycle. Might I remind you that the V8 has nearly 250 more components then the 3L it replaces. The G2 does not use an air pump, it is not currently nescasary. I'm not knocking the new design just stating the facts.

FACT: ETEC has 6 Electric AIR injectors and each builds pressure, they also lean the exhaust out and have to cool the Exhaust plate with engine water. The HPDI was about the same as a Optimax. Both of those use a pump system.

2 stroke was great and will be around for ever, look today old carb motor at the lake daily. EFI many, DFI plenty and 4 stroke is the new way to build a motor.

[Nova Kaw 650]

FACT: ETEC has 6 Electric AIR injectors and each builds pressure, they also lean the exhaust out and have to cool the Exhaust plate with engine water. The HPDI was about the same as a Optimax. Both of those use a pump system.

2 stroke was great and will be around for ever, look today old carb motor at the lake daily. EFI many, DFI plenty and 4 stroke is the new way to build a motor.

Ummm..... no. There's no air involved in BRP injectors.

To the 4-stroke detractors: manufacturers (other than BRP) are putting their research and development dollars into 4-stroke development. Eventually BRP will do the same when they lose too much market share. 2-strokes can't get by the "run lean; fry a piston" risk.

[yam911]

So technology could not have advanced to lighten the fuel delivery system as well ? How does KTM do it with motorcycles ?
Not saying you are wrong just wondering.

22R

The fuel systems could be significantly lightened and made more reliable and less costly IMO. Start with putting the EFI fuel pump in the boat tank. One pump, one filter, one pressure regulator on the motor. No VST, no fuel cooler, no lift pump(s),etc.. One return line to the tank. The system is continuously cleaning the gasoline. Fuel runs much cooler. Just model the system after that used in most automobiles and trucks.

[EuropeanAM]

The fuel systems could be significantly lightened and made more reliable and less costly IMO. Start with putting the EFI fuel pump in the boat tank. One pump, one filter, one pressure regulator on the motor. No VST, no fuel cooler, no lift pump(s),etc.. One return line to the tank. The system is continuously cleaning the gasoline. Fuel runs much cooler. Just model the system after that used in most automobiles and trucks.

There are some inherent risks involved in doing that... and that type of system is VERY costly when you factor in USCG, EPA, and ABYC requirements. Definitely "could" be done, but you wouldn't sell many due to the cost.

Just as a matter of clarification- HPDI and E-Tec don't use air pumps. They use crazy-high fuel pressures at the injector to atomize the fuel.

[FastCat04]

I agree with the above comments about there being other option besides air compressors, VST's, cooled fuel rails etc...but that would require engineering time and abandoning their present technology. Lean is clean but also yields detonation and crazy high combustion temps which often lead to piston seizure ( and broken rods---ie... it's currently on it's edge anyway). So, it's either pour more $ and time into 20yr old technology....or modernize. Fortunately for us avid speed freaks, we now have a game changing outboard !!!

Also consider this....you physically can't stuff a long enough connecting rod in a 2-stroke to get the correct rod ratio or piston weight to compete with modern 4-strokes. 2-strokes have notoriously short rods/long piston skirts and that rod angle can not produce the leverage that a long rod of a 4-stroke can. And furthermore..short rod motors have very short piston dwell times at TDC and BDC...which makes piston acceleration/deceleration a limiting factor as well.(ie...again back to broken rods.....again).

Everything is a trade off...yes carb'd 2-strokes are cool and light....but those aren't made anymore.....I'm personally ready to update and upgrade from my 2018 250 ProXS 2-stroke to the new technology !!!!

[lpugh]

I agree with the above comments about there being other option besides air compressors, VST's, cooled fuel rails etc...but that would require engineering time and abandoning their present technology. Lean is clean but also yields detonation and crazy high combustion temps which often lead to piston seizure ( and broken rods---ie... it's currently on it's edge anyway). So, it's either pour more $ and time into 20yr old technology....or modernize. Fortunately for us avid speed freaks, we now have a game changing outboard !!!

Also consider this....you physically can't stuff a long enough connecting rod in a 2-stroke to get the correct rod ratio or piston weight to compete with modern 4-strokes. 2-strokes have notoriously short rods/long piston skirts and that rod angle can not produce the leverage that a long rod of a 4-stroke can. And furthermore..short rod motors have very short piston dwell times at TDC and BDC...which makes piston acceleration/deceleration a limiting factor as well.(ie...again back to broken rods.....again).

Everything is a trade off...yes carb'd 2-strokes are cool and light....but those aren't made anymore.....I'm personally ready to update and upgrade from my 2018 250 ProXS 2-stroke to the new technology !!!!

I am impressed fastcat, most on this site have no idea what you just stated though

[Nova Kaw 650]

I agree with the above comments about there being other option besides air compressors, VST's, cooled fuel rails etc...but that would require engineering time and abandoning their present technology. Lean is clean but also yields detonation and crazy high combustion temps which often lead to piston seizure ( and broken rods---ie... it's currently on it's edge anyway). So, it's either pour more $ and time into 20yr old technology....or modernize. Fortunately for us avid speed freaks, we now have a game changing outboard !!!

Also consider this....you physically can't stuff a long enough connecting rod in a 2-stroke to get the correct rod ratio or piston weight to compete with modern 4-strokes. 2-strokes have notoriously short rods/long piston skirts and that rod angle can not produce the leverage that a long rod of a 4-stroke can. And furthermore..short rod motors have very short piston dwell times at TDC and BDC...which makes piston acceleration/deceleration a limiting factor as well.(ie...again back to broken rods.....again).

Everything is a trade off...yes carb'd 2-strokes are cool and light....but those aren't made anymore.....I'm personally ready to update and upgrade from my 2018 250 ProXS 2-stroke to the new technology !!!!

And imagine when the aftermarket comes out with performance cams for these new 4-strokes!

[2500]

Ummm..... no. There's no air involved in BRP injectors.

To the 4-stroke detractors: manufacturers (other than BRP) are putting their research and development dollars into 4-stroke development. Eventually BRP will do the same when they lose too much market share. 2-strokes can't get by the "run lean; fry a piston" risk.

Order a injector for etec and it has a air atomizer injector built in. 6 for each cylinder. It’s a self contained but does make pressure to atomize the fuel and spray pattern, not a pump like Opti but still make liquid fuel into a mist. So in my mind air.

[Nova Kaw 650]

Order a injector for etec and it has a air atomizer injector built in. 6 for each cylinder. It’s a self contained but does make pressure to atomize the fuel and spray pattern, not a pump like Opti but still make liquid fuel into a mist. So in my mind air.

Each injector is it's own extreme pressure miniature pump. It can atomize fuel about as fine as it can get. It can't make or use air.

[leo13]

The 3L engines have a reputation for being very sturdy. Are you sure you want to make the below statements comparing the rod to stroke ratios of 2 & 4 stroke engines? I believe the 3L has a 6.5" rod and a 3" stroke.

I agree with the above comments about there being other option besides air compressors, VST's, cooled fuel rails etc...but that would require engineering time and abandoning their present technology. Lean is clean but also yields detonation and crazy high combustion temps which often lead to piston seizure ( and broken rods---ie... it's currently on it's edge anyway). So, it's either pour more $ and time into 20yr old technology....or modernize. Fortunately for us avid speed freaks, we now have a game changing outboard !!!

Also consider this....you physically can't stuff a long enough connecting rod in a 2-stroke to get the correct rod ratio or piston weight to compete with modern 4-strokes. 2-strokes have notoriously short rods/long piston skirts and that rod angle can not produce the leverage that a long rod of a 4-stroke can. And furthermore..short rod motors have very short piston dwell times at TDC and BDC...which makes piston acceleration/deceleration a limiting factor as well.(ie...again back to broken rods.....again).

Everything is a trade off...yes carb'd 2-strokes are cool and light....but those aren't made anymore.....I'm personally ready to update and upgrade from my 2018 250 ProXS 2-stroke to the new technology !!!!