Mercruiser 5.0 starting problem

[Alphawater]

Tried to start my 2003 5.0 Mercruiser sterndrive today to winterize the engine. Initially the starting system acted normally as the engine turned over and almost started but didn't quite catch several times (boat has been sitting idle for over a month). Then when I tried the ignition switch again, nothing happened - thought I might have flooded the engine. Waited for a couple of minutes and tried again and the engine turned over and almost started again but not quite. After several tries, I could not get the ignition system to activate at all. I checked all fuses (ok), the circuit breaker switch (ok) the ignition switch connections (ok), the neutral position on the remote control, and the lanyard stop switch (ok). I even swapped out the ignition switch for another I had on hand - no change. Power is getting to all dash board functions. When I turn the ignition key, the temporary warning sound activates as normal (normally stops when engine starts and oil pressure increases). There is no clicking sound at the solenoid when I turn the ignition switch. If I was to guess, I am wondering if the remote control neutral position is the possible reason but not sure how to test. Not sure what to try next.

 

[Stinnett21]

Sounds like a dead battery. Even though things light up doesn't mean your battery has enough juice to turn the engine over. Recommend eliminating this first. Is this an MPI?

 

[Scott Danforth]

Battery voltage?

Check the cables for corrosion

Check voltage at the starter (both the B terminal and the S terminal)

 

[Scott06]

Tried to start my 2003 5.0 Mercruiser sterndrive today to winterize the engine. Initially the starting system acted normally as the engine turned over and almost started but didn't quite catch several times (boat has been sitting idle for over a month). Then when I tried the ignition switch again, nothing happened - thought I might have flooded the engine. Waited for a couple of minutes and tried again and the engine turned over and almost started again but not quite. After several tries, I could not get the ignition system to activate at all. I checked all fuses (ok), the circuit breaker switch (ok) the ignition switch connections (ok), the neutral position on the remote control, and the lanyard stop switch (ok). I even swapped out the ignition switch for another I had on hand - no change. Power is getting to all dash board functions. When I turn the ignition key, the temporary warning sound activates as normal (normally stops when engine starts and oil pressure increases). There is no clicking sound at the solenoid when I turn the ignition switch. If I was to guess, I am wondering if the remote control neutral position is the possible reason but not sure how to test. Not sure what to try next.

Would rule out some basic stuff like dead battery, loose or corroded battery cables (don’t forget ground cable too). Cycle shift to see if neutral safety is not making.
attached is wiring digram yellow red going to slave relay gets power when key is in start. Check for 12 v there. If none it is upstream of slave relay like neutral safety, cannon plug etc. If you do have 12 v at slave relay try jumping it at larger terminals on it. If stater turns you have a bad slave relay. If not starter or connections down there are bad.

 

[QBhoy]

Is this an mpi or carb ? If it’s an mpi I’d be thinking battery for the first behaviour. When it’s not doing anything at all..either as above or the relay on top of the engine is bad…or you have a dodgy connection at the battery or battery isolator