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Tehnical differences between Tohatsu Mfs 2.5a and 3.5 a

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silviustel

New member
Hello everyone.
I own a 2.5 hp 4 stroke Tohatsu mfs 2.5a manufactured în 2006. After buying a new carburetor because the old one was rubbished, it works just fine.
After exchanging the carburetor i kept reading online facts about Tohatsu outboards.
I found out that the differences between 2.5 and 3.5 hp 4 stroke models îs just the carburetor.
I studied the parts list for the two models and ideed, it's just the carburetor, more specific the Main nozzle and Main jet.
Did anybody make this mod? I have ordered the Main nozzle and jet for mfs3. 5a and i will mount them as soon as they arrive but i am curios if this is enough.
Thank you for the patience of reading.
 
Nope. The throat size is different. If you change jetting on the 2.5 to the 3.5 components, the mixture will be too rich. You need the bigger carb.
 
pvanv said:
Nope. The throat size is different. If you change jetting on the 2.5 to the 3.5 components, the mixture will be too rich. You need the bigger carb.
Click to expand...

Thank you for your reply. I thought so also. Although the intake and exit hole to the engine are the same size, maybe the inside of the carburetor is different. I ordered the parts already and i will give it a try anyway, but if it doesn't work I will buy the 3.5 carb.
I will post the results. Thank you.
 
The motor blocks -- crank, cam, castings, are all identical. The 3.5 carb has a larger throat. Changing to 3.5 jetting will flood the motor with too much fuel.
 
Ok. I got it. But if I buy the 3.5 carb will it fit plug and play and will run like factory setting for 3.5 or is there any other tune to make?
 
You were right. It works with the 3.5 main jet and nozzle but works unproper, does not accelerate the same and seems choked. I ordered a new 3.5 hp carburetor to make the upgrade. Anyway, to whom it may concern, to upgrade the Tohatsu MFS 2.5 to MFS 3.5 you need a new carburetor, code [FONT=&quot]3GV-03200-0.[/FONT]
 
Hi there,

I have a Mercury 4-stroke 2.5hp (manufactured in 2018) and am looking to increase the hp to 3.5. Much like the Tohatsu (to my knowledge this is basically the same motor as the Tohatsu), there is very little difference between the 2.5hp and 3.5hp model. Is replacing the carb to a 3.5hp the only part I would need to replace?

Thanks
 
This is an old thread; You should really make a new one. But, Yes, The Merc 2.5 is a re-badged Tohatsu, and the 3.5 carb 3GV032000M will work fine.
 
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