# 2006 Mercury 9.9 HP to 15 HP Conversion



## Chimpo (Nov 26, 2018)

I'm hoping that someone can help me out with this. I am going cross-eyed trying to read diagrams  

I'm looking for the part numbers required to convert my 2006 9.9HP to 15HP. From what I hear and read, it just a few parts inside the carb?

Aside from the obvious $2700 for a new 15HP, what do I need to make this conversion? 

2006, Mercury 9.9
Short Shaft, Non-Bigfoot
Model#1F10201FK
SN 0R068951


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## onthewater102 (Nov 27, 2018)

Sorry - not familiar with the 9.9 to 15 conversion, but if you're just seeing differences in the carb parts you might be correct as that's all there is for difference between the 20 HP and 25 HP 2 stroke Mercuries.


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## eshaw (Nov 28, 2018)

I'd go to one of the sites that sells parts, open a couple of tabs on your computer screen and do a side by side comparison on the two engines. That should show you any differences between the two.


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## wmk0002 (Nov 28, 2018)

As with any hp conversion you first have to confirm that they have the same block/displacement. Once you know they do, skip the carb and compare the intake manifold and exhaust components as those are common parts in down tuning 15hp. Then finally move to the carb. Ther of course may be other differences but these are the typical ones...they just allow more fuel/air to flow in and then exhaust to flow out better resulting in a higher rpm operating range.


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## Chimpo (Nov 28, 2018)

wmk0002 said:


> As with any hp conversion you first have to confirm that they have the same block/displacement. Once you know they do, skip the carb and compare the intake manifold and exhaust components as those are common parts in down tuning 15hp. Then finally move to the carb. Ther of course may be other differences but these are the typical ones...they just allow more fuel/air to flow in and then exhaust to flow out better resulting in a higher rpm operating range.



Thanks, I'll do that. I was hoping it would be easy and there was a site that sold conversion kits or something. Never seems to be the case in my life 

Hopefully it's just a few minor parts, or it won't be worth it to me. I'm not a speed freak, but it would be nice to pick up a couple MPH.

I appreciate all the advice.


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## JNG (Nov 28, 2018)

It won't be a few minor parts. It can be done on most 9.9/9.8 outboards (not all!) but it is NOT the old wives tale of JUST changing the carb jets. I say it's not worth it. Either be happy with the 9.9 or sell it as is for money towards a larger outboard.


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## Chimpo (Dec 19, 2018)

Well, my priorities have changed regarding this little motor. I drained the lower unit oil the other day because I heard a weird noise, and out came enough metal to fill a mouth full of cavities... :x 

Seems like all I can find online are long shafts, 2 stroke lowers, and big foots. Would a big foot work?

Anyone know of a good place to get a re-manufactured, or used 9.9 lower?


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## Pappy (Dec 19, 2018)

Convert the long shaft to a short shaft.


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## Chimpo (Dec 19, 2018)

Pappy said:


> Convert the long shaft to a short shaft.



I've dropped lowers to replace impellers, but I've never gotten into the inside of one. I assume it's a difficult task to replace the drive shaft?


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## Chimpo (Dec 20, 2018)

Chimpo said:


> Pappy said:
> 
> 
> > Convert the long shaft to a short shaft.
> ...



I removed the propeller shaft, and its associate assembly. So far it looks like I need a new reverse gear and pinion gear. The pinion is badly chewed up, and the reverse gear has one tooth pretty badly chipped. The forward gear looks good so far, but I can't fully inspect it.

I assume all the bearings will need replaced?

I removed the water pump housing, but I haven't figured out how to remove the pinion gear, thus freeing the drive shaft. The pinion looks like its pressed onto the driveshaft splines. I have a feeling I am going to need some sort of puller?

I've got the service manual on the way from eBay. Hopefully that sheds some light on my situation. 

Here are some pictures of the internals.

https://drive.google.com/folderview?id=15QWQ7ehVMsmw7yyTbbV8ilaxKYR-YIG8


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## Crazyboat (Dec 20, 2018)

I'm guessing you'll have to change props too, an extra 5 HP will need more pitch or dia.


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## Chimpo (Dec 20, 2018)

Crazyboat said:


> I'm guessing you'll have to change props too, an extra 5 HP will need more pitch or dia.



I'm going to start this secondary issue in a new thread. I gave up on the upgrade when I found metal in the lower unit oil.

https://www.tinboats.net/forum/viewtopic.php?f=4&t=45916


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