This blog post pertains mostly to Johnson and Evinrude motors, although some of this information may help with other makes as well. What you really need to find out is your part number. Sometimes this is as easy as just looking on the part fort it's stamped six digit number. Note that many websites you will need to add a 0 in front of this number for a search of the part. But if you can't find a stamped number follow the steps below....
The first step is determining what model # your outboard is. This can be found by looking on the left transom bracket clamp plate. Alternatively on the freeze plug of the block.
“The first step is determining what model # your outboard is. This can be found by looking on the left transom bracket clamp plate.”
The second step is to go to crowleymarine.com and put your model number in the search bar and then pressing enter. Now you should have your year and horsepower rating of your outboard.
The third step is to look through the different diagrams of your motor and determining what you part number is.
Now that you have your part number the final step is to type your part number in the same search bar that you put the model number into and pressing enter. After doing this and clicking on the listing there is a chart at the bottom of the page showing which year(s) this part will work with. Note: Some Johnson and Evinrude motors like the 25 and 35 HP models were bought with either a small 25 HP gearcase or a more beefy 35 HP gearcase. You will need the proper exhaust housing (midsection) for the those lowers to work with either one.