Nissan 4 hp 4 stroke NSF4A2 CARB question.

[Trapeze]

I have just purchased a brand new Nissan 4 hp 4 stroke 2005 NSF4A2D (2005 model year confirmed with Nissan using serial number, assembled late 2004) in the crate, Zero hours on it, never been out of the crate as far as I can tell.
Looked it over, wiped it down, filled the engine with oil, check the lower oil level, filled it with fuel and started it, runs like , well, new.

My question is about upgrading the 4 hp carburetor (3H9) to a 6 hp (3R4). The parts catalog shows the only difference between the carb on the NSF4A2 and NSF6A2 is the Main Nozzle, Main Jet and the Pilot jet. I read on this forum, in a post from 2009 that the venturi was bigger on the 6hp and I needed the whole carb in order to upgrade. Is this correct???

If I do need the whole carb, I also read on this forum to avoid the 3AU-03200-1 carb.
The preferred 6 hp Carb would be 3R4032000. Tohatsu Nissan states The part superseded to 3R4032001M. What is the difference in the two carbs?

Thanks a bunch,

 

[Sea Rider]

Need to swap 4 HP for a 6 HP carb, not just main internal parts as 6 HP carb has wider fuel passages. Bear in mind that the 4/5 HP models runs 4500-5500 min-max rpm. 6HP runs 5500-6000 min-max rpm. In order to get the full 6 HP out will need to go to a lower pitch prop for OB to rev at it's max wot range. Only cheable with an induction tach.

Happy Boating

 

[Trapeze]

Thanks Sea Rider,

I ordered a Tach yesterday, prop selection is in order in any case.

3R4032000 and 3R4032001M, What is the difference in the two carbs if any?

 

[pvanv]

Yes, you must change the entire carb. The older carb is NLA, so your part number question is moot. The final digit is for minor revisions; not 100% sure what minor change was made, but since you cannot get the older one anyway, it doesn't matter. The correct and best currently-available carb is:

3R4032001M

CARBURETOR ASSY, MFS/NSF6A2

$122.35

Yes, to get that last bit of power, you must run close to 6000 RPM.

 

[Trapeze]

Thank you Paul,

I have found a new old stock 3R4032000 for the same price, but I think I will go with the 3R4032001M