I have a saltwater mercury 150. When I get to ram and squeeze bulb until its firm the motor cranks and runs perfectly. I ran about 20 miles the other day and anchored and fished for a couple of hours. I tried to crank motor to leave and it would not start. Check bulb and it was spongy, I had to pump bulb for several minutes to get restarted. I took off and had no more issues. When boat sits it seems the bulb will get spongy and fuel system is not full of fuel. I have replaced bulb and no change it seemed better but now doing same thing. My fuel/water filter is located on back wall of boat ona european transom. What is best orientation of primer bulb in relation the filter more horizontal, vertical dies it matter?? Kinda got me scratching my head.
Best orientation for the bulb is with the fuel flowing “upward” through the bulb. That way gravity will help the balls sit on their seat when no fuel is flowing. Bulbs just don’t seem to last very long these days.