4.3 Mercruiser Crank, No Start

[Scott06]

However, when I use a spark tester, i get a steady blue spark. I started testing some of the wires and tracing them, and I’m not getting any power on the purple wire at the plug to the fuel pump.

You will not get any power to fuel pump if engine is not running and ignition is on unless you jump out the oil pressure switch. The purple yellow from starter is what supplies power during cranking. If you think is fuel related dump some gas down carb and crank it over.if you have ignition it will at least cough and run a bit.

since you have spark on gap tester are you sure rotor is getting spark from cap? Sounds like yiu might be loosing spark inside dist

 

[nola mike]

To get power at the purple wire at the pump the engine needs to be cranking over as the starter is delivering the power.

If just testing with key on, you won't see power there.

Purple wire is always hot with ignition on. Purple/yellow supplies the FP, purple only goes to the switch

 

[Joey9851]

Well, I finally got the answers to why it wouldn’t start. Water intrusion in cylinder three from a failed exhaust manifold. I found a reman locally for $1600 and had it inspected, new exhaust manifolds and installed and they finished up this morning. Still have to diagnose a tilt/trim issue but I think it’s low on fluid. It’ll go up but not down.