Tohatsu M25C3 Carb question

[Mako228]

I decided to rebuild the carb on my 2000 Tohatsu M25C3 as a winter project. I lost interest very quickly and now have the carb in pieces in a zip lock bag. My new winter project is to buy a new carb. I am considering ordering the M30A4 carb and having a dealer adjust the timing so I can get the 30hp.

Is this process that simple?
Any pitfalls?
Any recommendations?

Thank you for your help.

Sincerely,

Mike

 

[Sea Rider]

Re: Tohatsu M25C3 Carb question

The carb is same for both 25C3 & 30A4, which are the latest models, carb code is B03E for both. Save some bucks, if old carb is in inmaculate condition, no need to be shinny to work properly, just clean well all interior parts and assemble back. To know if in need to adjust throttle timing will need to know if magneto plate stops at 20? or 25? timing ?

If already set at 25? just need a new carb gasket which has larger internal diam. Part N? 346020110M
Paul can help you on this one...

Happy Boating

 

[Mako228]

Re: Tohatsu M25C3 Carb question

Thank you for the reply Sea Rider. I read somewhere (online) that the carb for the 30 hp has larger jets that deliver more fuel. In the parts manual the model number of the carb is the same for both (as you mentioned), but there is a note in the remarks section that states:

"30A4 # 35175
25C3 # 50039"

Any idea what this means?

Thanks again.

 

[TOHATSU GURU]

Re: Tohatsu M25C3 Carb question

The carb is the same for both the 25 and the 30, so the part number is the same. The serial number break is where the latest version of the carburetor was introduced when that parts book came out.

 

[Sea Rider]

Re: Tohatsu M25C3 Carb question

Yep, main nozzle and main jet are same for both models, the 25 is carb gasket restricted and sometimes -5 timing restricted, by this, carb's butterfly will never be opened at 180?. To check timing advance, place lever to forward, full throttle, if the carb white roller stops near or slight passing groove on middle throttle cam, it's restricted. If roller goes near all the way up on throttle cam high hill, is unrestricted. Check which factory timing you are dealing with.

Happy Boating

 

[Mako228]

Re: Tohatsu M25C3 Carb question

I decided to take my skirt off and went through the zip lock bag tonight. I got most of the carb re-assembled. The service manual was not overly helpfull. I mostly depended on the parts diagram.

The carb is not yet back on the motor, so I can not check if it is timing restricted. Are you saying that if the roller proved to be unrestricted I am all set after changing the gasket, if it is restricted I must also adjust the timing?

If this were your engine, would you set it up for 30, or would you keep it at 25? I run it on a 14' SIB.

Thank you both very much for your help.

 

[TOHATSU GURU]

Re: Tohatsu M25C3 Carb question

Forget the crap about the carb. Using your service manual check/set the timing as outlined to the 30 spec and just put the carb back on.

 

[pvanv]

Re: Tohatsu M25C3 Carb question

Forget the crap about the carb. Using your service manual check/set the timing as outlined to the 30 spec and just put the carb back on.

... using the 30 hp gasket, of course

 

[Mako228]

Re: Tohatsu M25C3 Carb question

Will Do!

Thanks very much.

 

[Sea Rider]

Re: Tohatsu M25C3 Carb question

Both 25 & 30 are 420 CC, the 25 is just restricted, if you are 20? timed, will gain the extra 5 HP when set to 25? timing, that's achieved at grip end. Start getting the 30 carb gasket.

You won't find in the service manual the procedure for mechanically tunning a 25 into a 30 in case you need to advance timing, as the grades? specified there for both model are only referential.

Happy Boating