Buy your Mercury 40 seal kit and marine grease here: https://bit.ly/Mercury-40-upper-seal-replacement
Buy only the Mercury 40HP seal kit here: https://www.boats.net/product/mercury/823547A03?utm_source=youtube&utm_medium=video&utm_campaign=description_atf_BDN
See how to do an upper seal replacement on your Mercury 40HP in this video from Boats.net.
We’ve already removed the lower unit, and if you need to see how to do that you can check out this video: https://youtu.be/ujX5rB6VIOI
John will start by getting the gearcase fluid out. Then, we’ll show you how to remove the prop and get the input shaft removed. During this process, we scratched the input shaft a little bit, and John will show you how to repair that.
With the input shaft removed, we’ll use our Mercury outboard seal kit to replace them. We’ll wrap up by reinstalling the input shaft.
See this diagram for a better look at the lower unit and input shaft seals: https://www.boats.net/catalog/mercury/outboard-by-year/mercury-outboard/2003/40HP/1a40412ad/gear-housing-driveshaft-2-1-gear-ratio?utm_source=youtube&utm_medium=video&utm_campaign=description_btf_BDN
Read how to do this job step by step: https://www.boats.net/blog/mercury/40hp/input/shaft/seal/replacement?utm_source=youtube&utm_medium=video&utm_campaign=description-blog-link
See how to replace the prop seals here: https://youtu.be/Pa_SBzaaK5o
Draining the lower unit – 0:50
Removing the prop – 1:00
Removing the pinion gear – 2:00
Removing old seals – 3:00
Replacing the seals – 4:35
Replacing the input shaft – 6:22
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In the video we’re working with a 2003 Mercury 40HP 4-stroke EFI outboard motor, but you may have similar steps for your Mercury outboard. If you’re not sure whether these steps apply to your motor, leave a comment and we’ll get back to you.
Mercury 40 water pump replacement:
Mercury 40 HP outboard oil change: