Keep in mind that no fuel bulb out there is approved for this type of use. Your M3-20B has an electric lift pump and you can easily jumper it off the solenoid with alligator clips while opening the bleed screw. Wear some nitrile gloves and have a diesel absorbing pad and bleeding these engines takes a few seconds.
1- Disconnect + feed to fuel pump insert alligator extension lead.
2- Clip extension lead to solenoid hot lug to make fuel pump kick on.
3- Crack bleed screw
4- When fuel flows close bleed screw
5- Run engine for sufficient time to ensure no entrapped air. If you still have air repeat above steps..
This is a fuel bulb I found cracked on a Trawler. The boat STILL SMELLS to this day.... Owner thought he had a leaking fuel tank.
If you must install a fuel priming bulb I would recommend a by-pass loop for it with positive shut offs on either side. But again your boat already has the tools you need to bleed the engine...