# Yamaha 15hp vs. 20hp



## Minnewaska (Feb 21, 2010)

If you choose the portable 15hp and 20hp next to each other on Yamaha's website (scroll down to see comparisons), they appear to be the exact same motor, other than the horsepower. Same displacement, size, weight, etc. Anyone know what that's all about?

Comparisons | Yamaha Outboards


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## chuck53 (Oct 13, 2009)

Very typical with a number of OB mfgs to have 2-3 different HP motors that appear to be the same motor. From what I understand, it's usually a difference in carboration that makes up the difference in HP rating.


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## FSMike (Jan 15, 2010)

Minnewaska said:


> If you choose the portable 15hp and 20hp ----


Portable?
Anyway, probably different carburetors.


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## SHNOOL (Jun 7, 2007)

Yeah this is pretty common... 
Merc 2.5 and 3.5
Merc 4, 5, and 6
Merc 8 and 9.9
etc.


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## Minnewaska (Feb 21, 2010)

FSMike said:


> Portable?
> Anyway, probably different carburetors.


Yea, portable, funny at over 100lbs. Their term.

There is roughly a $400 price difference between the 15hp and 20hp. No way the carb actually costs more, so the profit margin on the 20, must just be that much higher.

Makes one wonder if the 15hp carb can be modified into the 20hp carb, not that I think I'll go through the trouble.

This curiosity started, as I was contemplating putting a 15hp on the new dink, to save weight and cost. With no real savings in either, it would seem silly not to have the extra hp from the same motor, when you may wish you had it.


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## capecodda (Oct 6, 2009)

This is always worth checking when you buy a dingy motor. Yamaha I think the 4 and 6 HP are the same weight, as is the 8 and 9.9 HP. I ended up with a 6, same reasoning.


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## MarkofSeaLife (Nov 7, 2010)

Minnewaska said:


> Makes one wonder if the 15hp carb can be modified into the 20hp carb, not that I think I'll go through the trouble.
> 
> .


Yes it can. Voids warranty, of course, so its silly to do it to a new motor.

I was going to do it to my Merc 9.9 to make it a 15. Guess how much the new carb costs?

Go on, guess!

It is... (are you sure you have guessed yet?)

$400.

Sux, donnit?


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## Minnewaska (Feb 21, 2010)

MarkofSeaLife said:


> ......Sux, donnit?


I guessed $500, so there would be the illusion of value.


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## RobGallagher (Aug 22, 2001)

This is one of those lessons learned after I purchased a like new 6HP electric start merc. (from my 90+ yr old grandfather who put it on his credit card thinking he was gonna start clamming again but told not to pull start a motor because of his new pacemaker). I could not believe how heavy it was compared to my 4HP so I started doing the research.

I took it back to the Merc dealer and traded it in for a 5HP that was MUCH lighter.

So, IMHO, always buy the highest horsepower rating in the weight category.

I also always wondered about carb, and if you even need a bigger carb, or just new jets or other bits?


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## chip (Oct 23, 2008)

RobGallagher said:


> This is one of those lessons learned after I purchased a like new 6HP electric start merc. (from my 90+ yr old grandfather who put it on his credit card thinking he was gonna start clamming again but told not to pull start a motor because of his new pacemaker). I could not believe how heavy it was compared to my 4HP so I started doing the research.
> 
> I took it back to the Merc dealer and traded it in for a 5HP that was MUCH lighter.
> 
> ...


You sure it wasn't an 8? The Merc 4, 5, and 6 are all the same weight (except for the slight difference that come with different shaft lengths.)

Mercuries, Nissans, and recent Evenrudes in that size range are all made by Tohatsu, and the 4/5/6 in all of those brands is the same block. The 8/9.9 is the next block up, and the 15/20 after that. As others have said, they just dial back the power for the the lower HP ratings for each block with rev limiting and/or carb changes.

Yamaha does something similar. It's pretty common. It would likely be too expensive to engineer, produce, and carry parts for unique engines for such small changes in HP (in the grand scheme of outboards).


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## RobGallagher (Aug 22, 2001)

chip said:


> You sure it wasn't an 8? The Merc 4, 5, and 6 are all the same weight (except for the slight difference that come with different shaft lengths.)
> 
> Mercuries, Nissans, and recent Evenrudes in that size range are all made by Tohatsu, and the 4/5/6 in all of those brands is the same block. The 8/9.9 is the next block up, and the 15/20 after that. As others have said, they just dial back the power for the the lower HP ratings for each block with rev limiting and/or carb changes.
> 
> Yamaha does something similar. It's pretty common. It would likely be too expensive to engineer, produce, and carry parts for unique engines for such small changes in HP (in the grand scheme of outboards).


This was a two stroke. Probably around 2002. It definitely was a 6HP that I traded in for a 5 HP.

I understand the tooling and production issues. I don't understand the price variables as it seems it should cost just about the same to produce all the motors that use the same basic block, lower unit etc.


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## chip (Oct 23, 2008)

RobGallagher said:


> This was a two stroke. Probably around 2002. It definitely was a 6HP that I traded in for a 5 HP.
> 
> I understand the tooling and production issues. I don't understand the price variables as it seems it should cost just about the same to produce all the motors that use the same basic block, lower unit etc.


Ah, that makes sense about the 2-stroke.

I don't get the price difference either. I guess it's just pure market economics. Like you said, the highest HP for a given weight is the most desirable, so I guess they can charge more for it.


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