9.9hp 2 stroke vs 15hp 4 stroke

I have a 1985 evinrude 9.9 2 stroke and may have the opportunity to buy a 2006 Johnson 15hp 4 stroke. It is for a 14ft aluminum semi v boat. What are the advantages and disadvantages? Will there be much difference in power since the 15 is a 4 stroke? Thanks

Power will be roughly the same... fuel economy will be way better.

15 HP is 15 HP. My 2 stroke rule of thumb is a gallon per hour per 10hp at wot. This has been pretty accurate through all the small motors I have owned. A four stroke of the same hp will use about 80% of the fuel a 2 stroke will. It's a tough call to make the jump to a 4 stroke. They are quieter and more efficient, no mixing fuel, don't leave an Exxon Valdez looking oil slick behind you (slight exaggeration). Going to be heavier than that 9.9 but not an issue on a 14' boat. I still run the old 2 smokes but it's more about cost for me.

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Weldorthemagnificent said:

15 HP is 15 HP. My 2 stroke rule of thumb is a gallon per hour per 10hp at wot. This has been pretty accurate through all the small motors I have owned. A four stroke of the same hp will use about 80% of the fuel a 2 stroke will. It's a tough call to make the jump to a 4 stroke. They are quieter and more efficient, no mixing fuel, don't leave an Exxon Valdez looking oil slick behind you (slight exaggeration). Going to be heavier than that 9.9 but not an issue on a 14' boat. I still run the old 2 smokes but it's more about cost for me.

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It’s hard to beat the smiles per dollar of a good running 2 smoke.

Even if I were wanting to upgrade motors and there was only a $300-500 difference in price I would have to think long and hard about it.

For me $500 would be 10yrs worth of fuel.

Displacement per unit weight is my "thing". 20 lbs or more added to the transom can be an issue on a 14' tinny.

I have found outboard 4 strokes to be like making love to a blow up doll. Might get the job done..thats about all.

Go ahead and buy one and let us know what ya think..


If ya are looking for a change look for a 93' and up 15hp like the 9.9 ya have. They are larger displacement and ya will notice it right away with little added weight.

one is 15hp
the other is 9.9hp (maybe)

had a 9.9 briefly. Slug. noisy. hard to pull the rope. used more fuel than I thought it should (about the same as my current 25 4 stroke). Good for a 10 or 12' boat on 10hp restricted waters. 15 destroys it in everything but weight, a 15hp 4 stroke is going to be a little heavier but it is also more power, faster, gets out of the hole better uses about 1/4 of the fuel as a 9.9 2 stroke, much much much quieter operation, more confident idle, easier to start, no smoke, no mixing oil in with the fuel, but you gotta change oil once in a while big deal.

u be the judge. Having had both I will prefer 4 stroke, even with the extra weight

the newer motors are getting better and lighter, and if you buy a new one you don't take the chance of buying someone else's problem. EFI is real nice but an old carburetor can start and run just as well if it's set up properly

If you are making the jump from a 9.9 2-stroke to a 15 hp 4-stroke, my father-n-law did something similar. He got a brand new Honda with power tilt and electric start. You may want those bells and whistles if you make the jump.

The new Tohatsu 4-strokes are pretty light weight in the 9.8 to 20 hp sizes. The 9.8 carberated model only weighs 81.5 pounds in a short shaft. The 9.9, 15, 20hp fuel injected models all only weigh in at 95 pounds in short shaft models. Weight doesn't have to be a problem.