2011 Mercury four stroke 8HP upgrade?

[GordonL]

Hello everyone. I have a Tracker 1436 jon boat that I've added decks and storage to. I have lost a couple of mph due to the extra weight and I would like to get that back. I've heard the 9.9 can be upgraded to 15HP by changing the carburator. If that is true can I upgrade my 8HP by changing the carburator? Thanks for any info, I am having trouble finding all the specs for 2011 models.

 

[QBhoy]

Not sure if I can answer your question directly, but instead confuse the matter more Perhaps.
I’m not too up on the modern small mercs, but I know that the older 2 strokes almost aligned with what you said there. The 9.9, 10 and 15 were the same basic engines, but with carb differences (mainly). The 6 and the 8 were the same, but with similar carb variance.

So as far as the newer engines go…and relevant to your model, I’m not too sure, but I had in my head from long ago, that this didn’t apply in the same way to the newer 4 stroke. As far as I remember, the 8 and the 9.9 may have been the same basic engine but with variance in carb at least…but I think the 15 was a larger engine with regards to capacity perhaps. That said..there were a few variations of the 9.9 model too, I’m sure.
Have a wee look at the specs.
If you want your wee boat to perform a little better, personally I’d have a lovely late model 9.9/10/15hp 2 stroke Yamaha or merc on the back of her. Just can’t beat them for pound for pound power

 

[GordonL]

Not sure if I can answer your question directly, but instead confuse the matter more Perhaps.
I’m not too up on the modern small mercs, but I know that the older 2 strokes almost aligned with what you said there. The 9.9, 10 and 15 were the same basic engines, but with carb differences (mainly). The 6 and the 8 were the same, but with similar carb variance.

So as far as the newer engines go…and relevant to your model, I’m not too sure, but I had in my head from long ago, that this didn’t apply in the same way to the newer 4 stroke. As far as I remember, the 8 and the 9.9 may have been the same basic engine but with variance in carb at least…but I think the 15 was a larger engine with regards to capacity perhaps. That said..there were a few variations of the 9.9 model too, I’m sure.
Have a wee look at the specs.
If you want your wee boat to perform a little better, personally I’d have a lovely late model 9.9/10/15hp 2 stroke Yamaha or merc on the back of her. Just can’t beat them for pound for pound power

Thank you for the reply. I think the 8, 9.9 and 15HP were essentially the same for the 2011 model year. They were made in Japan I believe with Yamaha. I have not been able to find the specs for the 2011 models.

 

[airshot]

Is your 8 hp a two stroke ??

 

[airshot]

Oops...guess I should have looked more closely, now I see yours is a four stroke. To the best of my knowledge the carb trick only works on two stroke engines, not four stroke.

 

[GordonL]

Oops...guess I should have looked more closely, now I see yours is a four stroke. To the best of my knowledge the carb trick only works on two stroke engines, not four stroke.

Thanks!

 

[Scott Danforth]

The motor is tohatsu (all 40hp and lower mercs are tohatsu)

Your 8hp motor is similar to the 9.9 at 208cc, however more than a carb difference. The 15hp was larger if I recall

 

[GordonL]

The motor is tohatsu (all 40hp and lower mercs are tohatsu)

Your 8hp motor is similar to the 9.9 at 208cc, however more than a carb difference. The 15hp was larger if I recall

Thank you for your reply. I've read where several people have claimed to upgrade their 9.9 to 15HP. I guess that's why I assumed that they were similar. I know the specs for the 8 and 9.9 are the same, so I figured maybe there is a simple way to upgrade my 8HP. The first thing I will do this spring is to get a digital tachometer. I am thinking if I can get enough power to change the prop up one size than I can gain the 2-3 mph that I lost.

 

[airshot]

Thank you for your reply. I've read where several people have claimed to upgrade their 9.9 to 15HP. I guess that's why I assumed that they were similar. I know the specs for the 8 and 9.9 are the same, so I figured maybe there is a simple way to upgrade my 8HP. The first thing I will do this spring is to get a digital tachometer. I am thinking if I can get enough power to change the prop up one size than I can gain the 2-3 mph that I lost.

With only 8 hp, you wont gain anything noticible. One or so added hp will be lucky to add 1 mph. Your in a situation where your only real choice is to get a bigger motor !! If weight is an issue then go back to a two stroke motor.

 

[Scott Danforth]

Thank you for your reply. I've read where several people have claimed to upgrade their 9.9 to 15HP. I guess that's why I assumed that they were similar.

Many people updated their johnyrude 9.9's to 15 as they were the same displacement block and only differed by carb and timing

However if you think you can. Spend hours looking at parts manuals and service manuals to see if you can

 

[chanders]

Hello everyone. I have a Tracker 1436 jon boat that I've added decks and storage to. I have lost a couple of mph due to the extra weight and I would like to get that back. I've heard the 9.9 can be upgraded to 15HP by changing the carburator. If that is true can I upgrade my 8HP by changing the carburator? Thanks for any info, I am having trouble finding all the specs for 2011 models.

I do not believe you can go from 9.9 to 15. You can go 8 to 9.9 with carb change, and 15 to 20, but certain you can't go 9.9 to 15. Hope this helps..

 

[GordonL]

This is what confuses me...

Mercury 9.9 to 15HP Upgrade (2006 and Newer) 4-Stroke Outboard Carburetor

This carburetor upgrades the Mercury 9.9HP (2006 and Newer) 4-stroke outboard engines to 15hp. Fits both standard and Command Thrust models. No modifications are necessary, simply swap out the carburetor. This will not work on remote console versions of the outboard - only tiller driven models.

www.readysetboat.com

 

[Scott Danforth]

This is what confuses me...

Mercury 9.9 to 15HP Upgrade (2006 and Newer) 4-Stroke Outboard Carburetor

This carburetor upgrades the Mercury 9.9HP (2006 and Newer) 4-stroke outboard engines to 15hp. Fits both standard and Command Thrust models. No modifications are necessary, simply swap out the carburetor. This will not work on remote console versions of the outboard - only tiller driven models.

www.readysetboat.com

see post #10