Is Carb only difference between 25 & 30 HP?

[rp3703]

I am rebuilding a 1983 Mariner 25C 695 and while shopping for parts noticed a 30 HP carb that comes with a choke solenoid. I was already considering buying a choke solenoid anyhow but then the thought crossed my mind, could I throw a 30 HP carb on there as well and end up with a faster motor? Anyone have experience in these motors and know if the carb is the only difference between the two models?

 

[hardwater fisherman]

I think that 25 hp is the max. I think the 18 and 20 are the same but not the 30.

 

[flyingscott]

You have a Yamaha built mariner. You will have to do some digging in the Yamaha/Mariner series of engines. It may well be that it will work. The info from hardwater fisherman applies to American made 25 cid blocks only. It will not pertain to the yamaha built motors.

 

[hardwater fisherman]

Thanks for clearing that up.

 

[rp3703]

I have not checked every part number but currently, I'm trying to add electric start to the motor and noticed that the starter mount bracket fits 25-40. To me that would mean that the power head is the same size for the bolts to line up. Other than carburetor and without checking every part number, what else should I check?

 

[roscoe]

Intake baffle
timing
max rpm
inatke and exhaust porting
exhaust tube diameter

 

[GA_Boater]

Check the part numbers of the blocks. Porting changes will have different part numbers.

And of course you need these;

 

[jimmbo]

I have not checked every part number but currently, I'm trying to add electric start to the motor and noticed that the starter mount bracket fits 25-40. To me that would mean that the power head is the same size for the bolts to line up. Other than carburetor and without checking every part number, what else should I check?

That just means the mounting hole spacing are the same.