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Charles, Marine Mechanic
Category: Boat
Satisfied Customers: 3976
Experience:  US Navy (Ret) Certified Mercury Marine Tech with over a decade of repair experience.
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My 2003 150XR6 will only start with #1 cylinder spark plug

Customer Question

My 2003 150XR6 will only start with #1 cylinder spark plug taken out but still connected to the CDM? I replaced the Control Module, 2 power regulators and CDM #1, 3 and 5. Any thoughts?
Submitted: 1 year ago.
Category: Boat
Customer: replied 1 year ago.
I also checked all of the grounds on the engine block. I have to hold choke and press to full throttle to start with cylinder #1 out but still connected to CDM hanging touching plug below.
Customer: replied 1 year ago.
After the engine is at full heat temp with only running on 5 cylinders. I put the plug that is out back in. Then I will crank for like 15 seconds with the choke in and full throttle to start. When running, it runs like a brand new motor. It stays running too. Even at idle....
Expert:  Charles replied 1 year ago.

Hello, my name is***** will assist you.

Expert:  Charles replied 1 year ago.

The ground path of the CDM's go the the opposite side of the engine. Try swapping the ones that are in 1, 3, and 5 with the other 3 then see if the issue has moved to the other side or is still on the same side. If it did move, replace the original 2,, 4, and 6 CDM's