# Are today's 4-strokes more powerful than the old 2-strokes?



## Gotem (Mar 19, 2015)

Someone told me at a marina a 9.9 is a 9.9. It sounds simple enough, but don't they measure today's 9.9 at the prop or crankshaft compared to how they use to measure them back in the 70's and early 80's. My question is since there is a difference in how they measure the horsepower today, does that make modern outboards more powerful? Also if it is true, by how much or is the difference negligible?


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## Tallpine (Mar 19, 2015)

They changed the way they rated in 1983. Older motors were tested at the flywheel, after 83 at the prop shaft and the difference is very slight. Probably more important than horsepower between 2 stroke vs 4 stroke is the weight to hp ratio in practical aplication. Also, ratings are taken at certain rpms. So a 1990 15 hp Johnson 2 stroke may be rated at the same hp as another motor of equal hp, but the torque curve may be different. The same thing applies to 4 stroke versus 2. The 2 stroke is the quarterhorse of the two because of the hp to weight ratio.


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## Pappy (Mar 20, 2015)

Last time I said this the guy got all butt-hurt, knickers in a twist, and panties all in a wad but......

Experiencing a 4-stroke accelerating for me is like taking off in my Jeep in third gear. 

There is just not a good substitute for having a power stroke with each revolution vs every other revolution.


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## DaleH (Mar 20, 2015)

Pappy said:


> Last time I said this the guy got all butt-hurt, knickers in a twist, and panties all in a wad but......
> 
> Experiencing a 4-stroke accelerating for me is like taking off in my Jeep in third gear.
> 
> There is just not a good substitute for having a power stroke with each revolution vs every other revolution.


I agree with you, even though I love my DF250 Suzuki w/that huge 4-blade prop!

I also LOVE that commercial where they tie together, at the stern, 2 identical boats, one w/ an E-Tec DI 2stroke and the other with a Yam 4-stroke. They both take off and pull against each other and the E-Tec pulls the Yam motor under water. It's hilarious! 

... and can you tell I am NOT a fan of the bigger Yam dog-strokes? Oh, sorry I meant 4-strokes


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## turbotodd (Mar 21, 2015)

If the motor is set up correctly and propped correctly, there isn't a lot of difference. Other than fuel consumption, smoke (or lack of), etc. Weight is an issue on boats that are too small for the motor, like a lot of guys putting 25's on 1232's and 1432's. Or overpowering a bass boat rated for 150 hp, with a 225 or 250. Then weight becomes a problem. BIG problem with tiller steer motors that have manual tilt, unless it's got the tilt assist which is sweet.

There's always going to be the die hard smokers, and I were one of those until I personally bought one. Now I won't go back to a smoker. I thought I was going to hate it and bought it to just re-sell the whole rig. Ended up keeping the motor and selling the boat. I've had the motor for about 4 years now. Put about 50 hours or thereabouts on it. I've not had to make one single repair to it yet. Other than having to clean the carb once, it sat almost 4 months (my own fault). It was used, with unknown hours on it when I bought it. I had to force myself to think outside the box.

Ran a 2 stroke 25 (25MSHU)--twin cylinder twin carb yamaha on my boat for a while. Then sold it and put my 25 4 stroke on it. The MPH is almost exactly the same. The 4 stroke is on plane faster.


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## rabbit (Mar 23, 2015)

I traded a Mec 40 twin 2 stroke for a triple cylinder 4 stroke. The top end is about the same but the 4 stroke has more torque and planes the boat faster. It's much quieter, idles slower, is much smoother running. It burns much less fuel. Less oil and unburnt fuel in the water. No question the 4 stroke is a better motor even if it weighs 30 lbs more.
The 2 stroke might have a power to weight ratio that's better in some cases but the most powerful outboard in the world, now with a version that's over 600hp (Seven Marine) is a four stroke.


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## Seon (Mar 24, 2015)

Years ago I bought a Lowes CC with a 2 stroke Johnson used it to troll. Smoke got to me but I didn't want to fork out big $$ for a 4 stoke. After coming home several trips with headaches, I decided to plunged and bought a 4 stroke. No longer any smoke and much quieter. To me, the power was about the same. Never looked back.


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## lovedr79 (Mar 24, 2015)

i think the biggest differences are when used on small boats. the power to weight ratio of a two smoke are much better than a four stroke. but once you get into larger bass boats etc. there isnt much difference in power. the four strokes are super quiet and fuel efficient. the two smoke smells good and will keep mosquitos away. LOL!


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## jethro (Mar 31, 2015)

The top speed of both motors will likely be similar but the 4 stroke has something a 2 stroke does not, cannot and will not ever have- low end torque. So to the OP and the original question- 4 strokes are more powerful lower in the rev range than 2 strokes. Just the nature of the beast.


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## Captain Ahab (Mar 31, 2015)

Four stokes? Heck I rarely need more them 3


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## Pappy (Apr 1, 2015)

jethro said:


> The top speed of both motors will likely be similar but the 4 stroke has something a 2 stroke does not, cannot and will not ever have- low end torque. So to the OP and the original question- 4 strokes are more powerful lower in the rev range than 2 strokes. Just the nature of the beast.



Crickets.....I swear I hear crickets.......


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## DaleH (Apr 1, 2015)

Well, the truth is ... WHERE the torque curve lies IS a factor in performance, but at WOT ... HP is HP, less all of us only realize 90% of that if/when using ethanol-based fuels.

Many also may not realize that the motor YOU buy can be +/- 10% of the labled horsepower by Federal law. Years ago, when you saw OMC Stinger or High Output 'HO' motors, those are motors at the HIGH end of the rated HP band.

FWIW I worked at GE making jet engines for the Apache and Blackhawk helicopter lines and motors with highest HP were called "boomers" and were reserved for special operations duty.


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## onthewater102 (Apr 1, 2015)

You were right on the money with the different rating standards over time - an older motor with its power rating based on a measurement at the flywheel will not have the same power as a modern motor measured at the prop. 

HP is the amount of energy needed to accelerate 550lbs 1ft/sec, usually computed by the formulas [torque (in ft/lbs) * RPM]/5252 or wattage/746. When comparing old engines to newer ones the RPM speed at which the HP rating is taken is very important as it skews where you will experience the full power of the motor. My 1955 5.5hp isn't much, but it's rated at 4200 rpm vs. newer motors that are rated at 5k plus, so I have a lot more torque at lower engine rotation peeds with that than I would get out of a comparable modern motor which would need to be wound up to produce similar power. The difference is the greater torque will allow the engine to accelerate heavier loads faster than a less torquey motor that has to build up speed in order to generate more power.


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## xXOnyxXx (Apr 4, 2015)

here is a serious thought for you .... a 2 cylinder 2 stroke has like 5 moving parts to wear out .. crank, 2 rods, 2 pistons .... where as a 4 stroke 9.9 has like 50 .... more to wear out ... anyways i don't think ya will see 4 strokes running that are 50 year old .. i see 50's and 60's 2 strokes every weekend, just something to think about.


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## lovedr79 (Apr 4, 2015)

xXOnyxXx said:


> here is a serious thought for you .... a 2 cylinder 2 stroke has like 5 moving parts to wear out .. crank, 2 rods, 2 pistons .... where as a 4 stroke 9.9 has like 50 .... more to wear out ... anyways i don't think ya will see 4 strokes running that are 50 year old .. i see 50's and 60's 2 strokes every weekend, just something to think about.


Very good point. And they are simpme to rebuild without special tools.


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## onthewater102 (Apr 4, 2015)

Like this one 







1955 Johnson 5.5


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