9.9-15 hp carb identification

I have 80's vintage evinrude 9.9. Bought a 15hp carb on e-bay. Went to put it on and noticed venturi diameter on new carb was alot smaller than my 9.9,so i'm sure new carb is not a 15hp. E-bay seller said that it did come off of a 15hp. Would like to find out how and if a carb can be identified. Also there is a brass tube that runs vertical in the venturi of the new carb,which is probably a transfer tube.My 9.9 does not have this tube. Thanks for any help. Tranyrick.

Re: 9.9-15 hp carb identification

C/P:<br /><br />The outside visual dimensions of both carburetors appear the same, unless you look inside the throat. If you look in from the rear, you will have to position the throttle plate to a horizontal position to be able to see the throat very well. The 9.9 hp carburetor’s internal throat is .625 dia., 15 hp internal throat is .875 dia. up until late 1987 when they went to a plastic topped carburetor. The outlet or rear throat dia. is the same on both to match the manifold port dia. The idle jet venturi system is also slightly different between the two. The part number for the the pre 1987 9.9 hp Carburetor Assembly is #388936, while the 15 hp Carburetor Assembly is #338273. This increased dia. & larger main jet allowed it to breather better & pull more fuel in, increasing the RPM about 1000 RPM.