Fuel economy 2 stroke vs 4 stroke

"can someone tell me how much

"can someone tell me how much better the new 9.9 yamaha 4 strokes are on gas compared to the new 9.9 yamaha 2 strokes, is there that much differance.
thanks"

Depends on the application. A

Depends on the application. As a kicker (trolling) engine on a 20 to 30 foot boat the high thrust 4 stroke wins hands down. Less fuel and no 2 cycle oil. Much quieter and less noxiuos fumes.

"Since Rollie and I have varyi

"Since Rollie and I have varying opinions

Like he says however, depends on the application.

On the back of a 12 or 14 foot aluminum, the 75 pound 9.9 2 stroke will ultimately burn less gas than the 120 pound 4 stroke simply due to the 45 extra pounds (all else being equal).

Any difference you will notice? not likely (in the above application).

On a 100 hours of operation (recommended service interval) and say 40 gallons of gas burned -

2 stroke would require 1 gallon of 2 stroke oil (15-25 bucks depending on brand)

4 stroke would require 1 quart of 10W30 (2-5 bucks for "dino" oil, about double that for sythetic) and an oil filter ($13.75 from Yami)

In this horsepower, there is no significant advantage to either motor in terms of performance at top end - so it comes down to initial cost and on-going costs.

The on-going will be quite similar on a little motor. Yes, you have to buy 2 stroke oil, but you still have to do an oil/filter change on the 4 stroke (more economical the larger the engine). Plus there are far more moving parts on a 4 stroke than a 2, so more (potential) for things to go wrong....."

"I was careful to state as a &

"I was careful to state as a "kicker" on a heavier boat...lol There is no comparison to a "high thrust" 4 stroke 9.9 and a 2 stroke 9.9 trying to push that same heavy load. The 2 stoke with its smaller prop and gearcase has to rev up significantly more than the high thrust 9.9, therfor burning alot more fuel. (I too would opt for the 9.9 2 stroke on a light 12-14 foot aluminum cartopper) The 2008 9.9 4 strokes have no oil filter."

"To get 9.9hp which is a wot y

"To get 9.9hp which is a wot you need x amount of fuel, so theres not alot of difference running flat out but you will notice a big difference at lower speeds between 2stk and 4strk"

"hi guys thanks for the replys

"hi guys thanks for the replys i am looking at replacing 25 of my yamaha 9.9 2 stroke motors and cant decide if i should go with 2 or 4 strokes. looking for low maintenance and good fuel economy, as we live in the bush so i have to do all the maintenance myself and the nearest town is 3.5 hrs away.the boat are 14ft aluminum. thanks alot"

"Harold, in your particular ap

"Harold, in your particular application you must weigh a number of factors.

The questions anyone selling you a "fleet" of outboards should ask are -

How much run time do they see a year?
How often do you replace the engines?
How important is the weight of the engine?
How long is your operating season?

And a bunch of questions that don't even immediately come to mind.

If the extra weight of a 4 stroke isn't an issue and you can wait until seasons end to do all the required service and if you hold onto the motors long enough so that the any difference in price between the 2 and 4's is recovered, but you don't keep them so long that you get into the higher long term repair costs, then the 4's are probably a very viable option.

On the other hand, if the motors are regularly transported/carried to back lake locations or if they see alot of use during the season (300+ hours of use) without the opportunity to "take them down" to do some maintenance or if the price of the 2 stroke is significantly lower than the 4 or if you plan on keeping the motors in service for "many" years I may tend to go with the 2 stroke.

Generally, the routine maintenance on the motors will be roughly the same. They both need spark plugs once a year, an impeller every second year. They will need "winterizing" when they are layed up and both have to be "returned to service" in a similar fashion at the start of the season.

You will need to change the oil on the 4 strokes at the recommended interval (100 or 200 hours or whatever) - or you will have to add 2 stroke oil to every tank of gas at the mix rate - that's something that you need to decide which is more "practical" for you.

We are only talking about a 9.9 model, so for the 4, a valve adjustment every second year (since this is a commerical application) would probably be sufficient to keep them running well.

I really am pro-2-stroke, but don't get me wrong here. I will never tell anyone that it's harder to work on a 4 stroke - that's not true. Is there a little more maintenance to do? ABSOLUTELY.

And that is where I have the problem with the motors. The "average" owner never really looked after their old 2 strokes, and to some degree that was ok - they can take fairly significant abuse/neglect and will still fire right up for you.

The 4's are not so forgiving. So in 5 years time they have a very expensive to fix, heavy chunk of scrap aluminum on their hands.

As has been stated in other posts here. You won't really see a difference in fuel economy at this horsepower. Even if on paper the 4 was say 10% more fuel efficient, it weighs about 60% more than the 2 stroke model - and it costs you gas to push that extra weight.

On the other hand, if you are equipped (and willing) to do all the maintenance yourself (or on-site), as Rollie points out, you could save yourself alot of 2 stroke oil costs, by running the 4's. And that can add up on a little motor quite quickly when you are running 25 of them...."

"Harold you own a hire busines

"Harold you own a hire business and the customers who hire your rigs will run them flat out for most of there life, the two stroke has half the moving parts of a 4stk,lighter to lift on and off,they will be easyier to maintain than a 4stk.
I have serviced more 4stk,s than i have had hot dinners and the oil looks very dirty after 100hrs, you would be changing oil every 50 hours to ensure longevity of the 4stk."

"I really agree with Jamie on

"I really agree with Jamie on this one.

I'm not totally against 4 strokes, but as he eludes, I believe they are more of a "personal" engine that has to be (babied - maybe not the right word, but close enough) compared to 2 stroke models which were almost designed with a "little abuse" in mind..."

"When i owned my own business

"When i owned my own business OMC dealership i gave my dad an outboard for his boat and over time he had 8 motors on his 12ft boat cause i kept selling them..the last one was a 9.9hp 4stk and i bought it for him new in 96 and he loved it.
I use to service it every 20hrs for him probely overkill but it cost me nothing to do this for him.

If i were buying a outboard i would buy a 4stk and yes I would baby it but i would not hire it out"

"The other question is, how ma

"The other question is, how many more years will it be before 2 strokes are outlawed in new sales. I do see that coming eventually. Also an interesting conversation today with a whale watcher here on Vancouver Island. None of the (60 or so companies in Victoria) will dare run 2 strokes as the public perception is not favourable. Especially in an eco-tourism based business!"

Rollie your right I see that h

Rollie your right I see that here in Australia as well. Wont be long befor no carby model 2stks are built only 4stks and direct injection mdl 2 stks

4 stroke

trust me

2 stok

4 stroke

trust me

2 stokes are going 2 be phased out by 2015!!!

I dont think direct injected 2

I dont think direct injected 2stks will be phased out as the meet the emission standards.

But they will not produce carby models

JIT is right all 2 strokes wil

JIT is right all 2 strokes will go. That is what I've heard as well. 2 strokes can't get away from the fact they burn oil as part of normal operation. Its a 2 prong effect...legislated out of the market..and to low a demand for product for manufactures to continue the line.

"Yes, I have seen a few of the

"Yes, I have seen a few of the 2010 EPA changes being thrown around.

The two big ones I've heard include -

(banning) carbs from outboards - not sure how the mfg's will takle that one in the small outboard segment - a fuel injected single cylinder 4 horse just don't seem right

installation of catalytic converters on inboards/IO's (I believe that Mercruiser already has made changes so that at least this years models can be adapted for Cat's).

But agree with Jaimie as well - as long as the DFI 2 strokes keep their C.A.R.B. ratings up there, they will stay on the market. BRP/OMC is betting on that one, since that's all they make.

And unless Asia, particularly China gets onboard with the big "GREEN" push, 2 strokes will continue to be available outside of the US where the EPA can reach. If a billion Chinese still want a 2 stroke, there will be a market.."

"Graham
since 2000 in KALIFOR

"Graham
since 2000 in KALIFORNIA no carbs on a 2-stroke could be sold, i believe NY/NJ also

any i/o boat from built 01/2008 has cats on them, 2010 for all other states

DFI i still think is better than 4 stroke, but no body has a 9.9HP DFI yet!"

"2stk vs 4stk it is a great su

"2stk vs 4stk it is a great subject

This is my opinion but no matter what way you swing there are swings and round a bouts.

A 2stk has high hydrocarbons out the exhaust which scientist say is leading to the hole in the ozone layer and global warming.

The 4stk has high nitros oxide levels much much higher than a 2stk. which is also very bad and to reduce nitrous oxide levels in an exhaust system you need hydrocabons...i think its a double edged sword."