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Author Topic:   Cost of Ownership: 2 sroke vs. 4 stroke
LarrySherman posted 09-05-2001 10:32 AM ET (US)   Profile for LarrySherman   Send Email to LarrySherman  
Being potentially faced with a purchase decision in the near future, I thought it would make sense to run the numbers on 2 stoke vs. 4 stroke technology.

My first cut at this is below, but I am fairly new to the world of outboard ownership, so please, correct me where I'm wrong.

I assume a nominal season of 1000 gallons for a 2 stroke engine.

I assume gas costs $2.00 per gallon.

I assume premix of 50:1 for 2 strokes, using guality oil ($20/gallon)

I assume 2 oil changes per season, 4 quarts each, @ $5.00 per quart.

I assume a 30% increase in efficency in 4 stroke motors, with a commensurate reduction in gas usage.

I assume a 6 year engine life.

----------2 STROKE-------4 STROKE

GAS------ $2000.00-------$1400.00
Ring Free---$50.00------------N/A


Looks like a $1010.00 savings per year. Or $6060.00 over 6 years.

It seems to me that if these numbers hold up, an F255 Yamaha (or the like) will pay for itself in the first three years of ownership.

Am I correct?

triblet posted 09-05-2001 10:42 AM ET (US)     Profile for triblet  Send Email to triblet     
I think your oil prices are high. You can
find premium TCW-3 for $10-12/gal. You
shouldn't pay over $1/qt for four-stroke

1000 gallons is a LOT of gas, at least to me.

But I think you are in the right ballpark.


acseatsri posted 09-05-2001 10:50 AM ET (US)     Profile for acseatsri  Send Email to acseatsri     
I would also think that the longevity of the 4-stroke would be better than a 2-stroke. Scored piston walls and seized rings shouldn't be a factor given that the oil is constantly being splashed on the walls. And little or no carbon build-up should be evident because no oil is being burned. Just my 2 cents.
LarrySherman posted 09-05-2001 11:23 AM ET (US)     Profile for LarrySherman  Send Email to LarrySherman     
Ok, a revision:

----------2 STROKE-------4 STROKE

GAS------ $2000.00-------$1400.00
Ring Free---$50.00------------N/A
10W30----------N/A-------- $16.00


Looks like a $834.00 savings per year. Or $5004.00 over 6 years.

If I cut the gas use in half, to 500 gallons a season,

----------2 STROKE-------4 STROKE

GAS------ $1000.00--------$700.00
Ring Free---$25.00------------N/A
10W30----------N/A--------- $8.00


Looks like a $417.00 savings per year. Or $2502.00 over 6 years.

Not so favorable now.

We need some info on gas usage on different hull types, and engine rigs, as well as some "average" usage patterens for different regional areas. We can then get 2 coefficients to plug into the formula to determine the payoff. Do you agree?

LarrySherman posted 09-05-2001 11:59 AM ET (US)     Profile for LarrySherman  Send Email to LarrySherman     
JimH posts this formula in a fuel Consumption post:
For 2-stroke engines, compute WOT fuel consumption:

Fuel (GPH) = Horsepower/9.1

For 4-stroke engines, compute WOT fuel comsumption:

Fuel (GPH) = Horsepower/10.5

To approximate consumption at lower throttle settings, use this formula:


For 2-cycle engine EXP= 1.5
For 4-stroke engine EXP=1.7

Jim, how did you derive the factors for your 2 and 4 stroke values?

How did you arrive at 9.1 for 2 and 10.5 for 4 strokes when WOT GPH numbers?

This is great stuff. Now there was a thread that had a hull type coefficient...I'll go look...

Peter posted 09-05-2001 01:16 PM ET (US)     Profile for Peter  Send Email to Peter     

I think your consumable estimates are a bit on the high side for use solely up here. They might be more realistic for average year round use in Florida.

For example, since the middle of May when I launched for the season, I've run about 800 miles. That's using the boat virtually every weekend (both Saturday and Sunday) since May and a few days during the week here and there. I get 2.5 mpg so that 800 miles translates into approximately 320 gallons of fuel so far at $2/gallon ($640). I've burned about 5 gallons of Yamalube at about $12/gallon (~$60). I've used about 20 ounces (1 oz per 15 gallons of gas) of RingFree which goes for less than about $1.00/ounce, but figure $1.00 for ease of calculation ($20.00). So far my consumables operating tab has been about $720.00. Let's say that I continue the same usage and the season is 2/3's over. Thus, when the season is over and I will have burned about 475 gallons of gas, 8 gallons of 2 cycle oil and 32 ounces of Ring Free traveling about 1200 miles. I figure my consumables operating tab will be under about $1,100.

Now, let's say that the 25 Outrage with a 250 gets only 2.0 miles per gallon under the same usage. It will have burned 600 gallons of gas, consumed about 12 gallons of 2cycle oil and 40 ounces of RingFree for a consumables tab of about $1400.00.

I am not sure, but I believe that the efficiency differences for a 4 stroke versus a 2 stroke decline as engine speed goes up. Unfortunately, Yamaha doesn't have a published performance report for the F225 yet. The best comparison I can find is between a 4 stroke 115 and a 2 stroke carbed 115. There is a 30 percent difference in fuel economy at WOT. That difference might be less between a 4 stroke and a 2 stroke EFI.

Let's use 30 percent though. For me, under the above example, the same usage with a 4 stroke 225 will save about 110 gallons of gas, 8 gallons of 2 cycle oil and 32 ounces of Ring Free. Total cost savings on consumables amount to about $350 per season.

If there is a $3000 premium for the 4 stroke over the 2 stroke EFI, then it looks like it might take 8.5 seasons to recover the price difference under the example applied. To me, that's a pretty long time.

The unknown here is how much will it cost to maintain the 4 stroke versus the 2 stroke?

As a rough rule of thumb, figure that a 250 on a 25 Outrage would get 2 mpg.

To burn 1000 gallons, you'd have to go 2000 miles.

Bigshot posted 09-05-2001 02:20 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
This is a hard one to figure due to everyones different style and boat. On a Montauk a 4 stroke burns about 1 gph less than a 2 which is roughly 25% at cruise. A 90 hp 4 stroke is roughly $2k more than a 2stroke so therefore I assume somewhere around 1000 hours before breakeven(@$2 per gal) with oil and such. Can't do this by year, have to do it by hours. For some it might pay off in 2 years. $ strokes have to be tuned up where 2's really does not. A 4 is a bit more extensive on winterizing than a 2 I assume also.

Now what about your oportunity cost on that $2k. At 10% growth rate it would be roughly $3k in 4 years or at 10% interest(if financed) it would cost you roughly $2600 over 48 months including tax. So if you spend the extra $2K it actually costs you alot more. Now if you invested the $2k in stocks last year instead of buying the 4 stroke, you missed out on a free upgrade:)

LarrySherman posted 09-05-2001 09:11 PM ET (US)     Profile for LarrySherman  Send Email to LarrySherman     
Thanks Peter and BigShot, this is exactly the info I needed. IE, it's just not a clear win to gor four stroke at this point. Now it the government gave you a tax break on the purchase of the motor, we'd be in the ball park I think.

It appears that my 235 is repairable, so I may not be buying as soon as I thought. I thinkt this is a great thread though. I'm going to do some research and get back to this soon.

Peter posted 09-05-2001 09:41 PM ET (US)     Profile for Peter  Send Email to Peter     

Up here, I would say 100 hours per season (guessing 5 hours per week, 20 weeks) is probably on the verge of being high usage. So based on the 1000 hour threshold, it would take 10 seasons for payback. Very interesting. To make the analysis more complete, one needs to factor in the environmental cost of operation somehow. That's a hard one to quantify.

Bigshot posted 09-06-2001 10:13 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
That is a hard one, the whole enchilada is tough. It is wisper quiet, longer range, more weight, more expensive to repair, etc. not apples to apples. Most people would never hit breakeven. I bet most people up North(me when I lived there)who did little or no trolling and went out every weekend only do 50-70 hours per year. The only time in NJ I did 94 hours(with a F/T job)was in 94 with a brand new boat that I picked up on 3/12 and pulled around Thanksgiving. I usually avg'd 60hrs per. In Fl I do about 120-150 per. For those of you without an hour gauge, it is like a GPS, you will be amazed at how much driving it takes to put 60 hrs a season on.
LarrySherman posted 09-06-2001 02:17 PM ET (US)     Profile for LarrySherman  Send Email to LarrySherman     
As long as the compression is there, I think I will feel better taking my friends and family out on the boat if I get the motor gone over by a professional.

Here are some prices from

SX250TXRA 25" $11,472.00
F225TXRA 25" $13,254.00

Jurisproodenz posted 09-06-2001 02:50 PM ET (US)     Profile for Jurisproodenz  Send Email to Jurisproodenz     
I think that most of the elements have been hit, including the time value of the money. However, an important aspect is residual value. Statistically, most people don't own their boats for that long (6 years). Rather the velocity of ownership looks to be something nearer two to three years per boat. At that rate the four stroker may pay back in residual value where it is clearly an up-front liability as compared to an EFI. I don't know the actual anticipated residuals on the large four strokes, but given increasing pressure on the boating community to clean up its act with regards to emissions, I'd guess that a four stroke will have more appeal in the coming years. We all know that once you hang a two stroke on your transom, you have pretty much written off 30% right there. What will that be for the four stroke?

This seems to be an analog of the diesel versus gas for inboards debate. Simply put, you have to use the hell out of your diesel to make it worth the while in terms of running costs. Plus more expensive repairs, overhauls, winterization, weight and other things. But residuals are rock-solid with diesels. Some boats don't even seem to depreciate in absolute terms. Since Larry's boat is likely not too weight sensitive, the residual value of the four stroke may be important to him?

BTW I concur as to hours: I barely made 150 hours in my most fanatic year. There's simply too much winter around here.

Peter posted 09-06-2001 02:59 PM ET (US)     Profile for Peter  Send Email to Peter     

Those look like very good prices. However, I believe the quote is motor only -- no prop, wiring harness, helm control, ignition switch, cables, gauges or oil tank. These probably add another $1.5k to the tab. Also, for the motor alone, I doubt you'll be able to get those prices around here. When the time comes for repower, also factor in about $350 for rigging and testing labor (8 hour labor charge at $70/hr).

LarrySherman posted 09-06-2001 03:25 PM ET (US)     Profile for LarrySherman  Send Email to LarrySherman     
Yup, behind those prices is Central Florida Yamaha. I very much doubt I would have a good service relationship with my local Yamaha dealer if I went this way. I can't see it working.

I think you have to have a relationship with your shop.

LarrySherman posted 09-06-2001 03:30 PM ET (US)     Profile for LarrySherman  Send Email to LarrySherman     
Thats a very good point that I had not considered Juris. I think that the residual vaue on 2 and 4 stroke must be on inverse curves, with 2's going down and 4's going up. And DFI's I think will suffer the most, seen in a few years as strange blip on the evolution of outboard technology.
Bigshot posted 09-06-2001 03:48 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Told ya it is a hard debate. Go with what you want, shop around, and you will be happy. Settle and you will regret it. same thing goes with single vs twins, bottom wax vs paint, bunk vs rollers, etc. It is all your personal preference and ability to incure debt. The only thing I recommend is do not underpower. If you want a 250, suck it up because if that 200 or 225 is too slow with 4 adults you are gonna regret the extra $$ you pinched, etc. I am debating the whole thing just for the noise factor but weight is such an issue on the Montauk(in my opinion).
Peter posted 09-06-2001 09:23 PM ET (US)     Profile for Peter  Send Email to Peter     
Totally agree with BS and LHG, don't skimp on the HP. If you go single, get a 250. If you go twins, get as close to the 300 rating as you can. You don't have to use all the HP but its there when you need it. Also, the larger HP engine will last longer because it won't be working as hard at the typical cruise speed you'll most likely being doing most of the time.

Jurisproodenz posted 09-07-2001 11:54 AM ET (US)     Profile for Jurisproodenz  Send Email to Jurisproodenz     
At the risk of being repetitive: I totally agree with the previous posts. In my humble opinion, you simply cannot have enough power for those moments that you NEED it -- I have outrun thunderstorms to get to the harbor in the nick of time.

It is far better to loaf along with little strain on the engines than to have a 15 second hole shot while your ponies summon up the extra zap to get you on top. And you will have a more reliable engine in the long term.

Lastly, an underpowered boat is always harder to sell when the time comes.

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