2004 mercruiser 5.7 L MCM

[Pusher]

My dads got a 5.7 liter mercruiser with problems that have plagued him all season.

The motor was factory new in 2004


It's Carburated (new carburator in the last three years)
It starts cold just fine
Once it warms up & idles down and you rev it up it does fine, but if you pull back on the throttle afterwards it will die on de-acceleraction

Two shots of the accelerator pump will start it back up fine but it won't start easily without it.

We've also had issues with the Purple - yellow ignition wire melting either while cranking or right after cranking

When it melted, the wire from the key to the carb was replaced.

This problem started recently.

We have put a fresh water cooler on
New alternator
New fuel pump
Factory new Carburator
Oil presure switch
Wiring harness
Ignition switch
Ground points cleaned
New battery

I really don't know what else to do. Redneckjoe did you have a similar issue?

Thanks for the help guys!

 

[Pusher]

Sorry, the carburator was replaced 16 months ago.

The harness wasn't replaced. The wires that were melted were replaced though.

 

[alldodge]

Do you have an engine serial number?
The Pur/Yel wire connects from the starter, to electric choke and fuel pump. Once starter stops cranking and motor starts power continues to be supplied thru the oil pressure switch. This wire should not go back to the key. Which part of the wire was replaced?

 

[kenny nunez]

A rotor will sometime ground out to the shaft when coming off of plane. That is when the ignition has most load than when on a plane. This was a common problem with the in line engines. You also said that the points were ground, should your engine have electronic ignition?