How to identify lower unit casing part number?

[Kinoruqmii]

I am replacing a lower unit (not sure what model it came off of) on my 09 F90, and have found one that fits and runs in the outboard. However, it is a counter rotating (left hand) gear set. I would like to replace the gear set with a standard rotation (right hand), but can't find the part number on the casing to ensure that the correct gear set for the 09 F90 will fit and or work properly.

FYI, I had previously taken apart the lower gear set to replace the 25" shaft (appears to be one for a two stroke model), with a 20" shaft, and re-constructed everything per service manual instructions. I didn't take particular notice of the gear set (other than to see that they were in near new condition).
Upon installing it in the outboard, and testing it (on a trailer), we then noticed it was a counter-rotating model.

I bought a LH 17pitch prop for it, and it runs fine, but I would like to switch it out to a standard rotation set up, but before purchasing the appropriate gear set, I want to verify that it will be compatible with the existing lower unit.

I can't find any numbers stamped into the lower unit casing.

Any suggestions as how to determine the part number of the lower unit casing before I order the right hand gear set?

[Sequoiha]

from my dealing with yamaha for over 20 years, the counter housing is different than the standard rotation housing,, they are built and cast different,, and the gear sets cannot be swapped.. I know they are on the V6 motors Im pretty sure it is the same on the smaller ones.

[Kinoruqmii]

In my brief research on-line from various websites offering Parts finders for Yamaha outboards, I found that the 2000 F115TLRY and the 2000 LF115TXRY (L designating a counter-rotating model) shared the same casing (part # 6E5-45301-05-8D). The gear set part numbers are different (of course), but everything else seems to be identical.

Any ideas or suggestions are helpful.

[boscoe99]

What country are you from? The reason that I ask is because only the F90 is sold here in the states. Yamaha USA do not offer an LF90.

Here is what I recommend. Find a parts catalog for both your F90 and and LF90 of approximately the same model year. Go to the illustration labeled "Lower Casing Drive". Look at the part number for the "Casing, Lower". It will usually be Ref-No 2.

If you can't find a parts catalog ping Mr. Almetelo here on this website. He has access to lots of Yamaha data that I don't.

If the part numbers are the same then well and good. You can just change gear sets. If the part numbers for the casing are not the same then all bets are off.

Some times the casing part number is the same. Some times it is not. Here is an example of where it is the same. Many examples can be found where it is not.

[Kinoruqmii]

I was offered the replacement lower unit from an uncle (he doesn't recall where he bought it from), so I am not sure where to start to find the part numbers to locate what exact model it came off of. I know that Yamaha USA doesn't offer a counter-rotating F90 model.

Usually the casing has its part number stamped somewhere on it, but I couldn't find it on this one. I was hoping someone might have some suggestion as to where it (stamped part number) might be "hidden".

[boscoe99]

The only Yamaha part that I have ever seen that has a complete part number is the main engine wire harness.

The lower unit casing will typically have just a three digit code that might indicate what model usage it has. That code is down inside a cavity on the lower unit when looking from above.

[almetelo]

best of my knowledge from parts manuals I have seen is that Yamaha F80/F100 (world market) F75/F90 (US/CAN market) and F95 (Japan market) does not offer counter rotation for this models.

Only F115/LF115 and above HP.

I know F115 use some parts used on the above models (or vice versa) but I don't know if lower unit it that the case and now I dont have the time to have a look on parts manual to check this (But I guess is not interchangeable )