I would go with the Sierra kit, because it has everything the Mallory kit has plus it has the float needle clip, which helps prevent the float needle from getting stuck. I didn't see the float needle clip in the Mallory kit.
Pappy, is speaking the gospel here. Don't take short cuts when it comes to cleaning your carburetor, you will enjoy good running and low idling. I have a 1984 Evinrude 15hp and she runs great and idles wonderfully. So, you have a very well built motor and will give you years of good service if you treat her right. That starts with a good clean up with your carb.
Here is a link to a good set of articles related specifically to your motor. The author did a wonderful job of putting all that information together. It will help you maintain and even do some repairs if needed.
https://www.sschapterpsa.com/ramblings/OMC/OMC%20info.htm
Here is a link with a parts diagrams and you can order stuff from them as well.
https://www.marineengine.com/parts/johnson-evinrude-parts.php?year=1988&hp=15
Be careful, if you soak your carburetor. Remove all the plastic or rubber parts, the carburetor cleaner will dissolve and eat up plastic and rubber pieces. **Your carburetor may have a black plastic bowl type so, be very careful!!!***
Oh, by the way your fuel to oil ratio is 50:1 mixture. That is 16 ounce of TWC-3 marine 2cycle
oil to 6 gallons of fresh 87 octane unleaded fuel!!