Re: 1969 85 hp evinrude hydro electric issues
The solenoid plungers must be adjusted so that they are lower than the top surface of the solenoids, approximately 1/64" lower, BUT no lower than 1/64". Any deviation will result in shift problems. However, this has nothing to do with having a solenoid fail electrical in any manner.
Those solenoids are designed to have 12 volts applied to them constantly. This brings a question into view........... Are you running a dual battery setup? If so, that might indicate that somehow you are applying 24 volts to that solenoid. I can think of nothing else that that would burn out one solenoid regardless of the time period.
You mention "My blocking diode behind the dash heats up because of the increased current". This diode is also designed to handle 12 volts constantly which again brings to mind the 24 volt mention as stated above.
The purpose of the blocking diode is to allow voltage to flow from the ignition switch directly to the power terminal of the shift switch. This terminal also connects to the shift diode, (commonly called monkey nuts due to its appearance), asembly at the engine's strip terminal and from there to the engine's charging system (rectifer & stator). If the blocking diode at the ignition switch fails, it is impossibly to shut the engine down due to the fact that the charging system would be applying voltage to the ignition system via the failed diode.
If the rectifier or the shift blocking diode assembly at the engine failed, then obviously shift and charging problems would exist....... and weird voltage problems will arise.
Check the rectifier and shift blocking diode at the engine with an ohm meter first.
Also with a ohm meter, check the blocking diode at the ignition switch to make sure that voltage/continuity flows only one way...... from the ignition switch to the shift switch power terminal.
With the engine NOT RUNNING but with the key in the ON position, check to see that you have 12 volts to the solenoids, that is....... NO voltage when in forward...... 12 volts to only the GREEN wire (neutral solenoid) when in NEUTRAL..... and 12 volts to both the GREEN and BLUE wire (neutral & reverse solenoid) when in REVERSE.
Now IF you have 12 volts at the ignition switch side of that small blocking diode BUT less than 12 volts at either of those solenoids, a problem exists such as frayed wiring, loose connections, etc that is creating a voltage drop. If this type problem exists, it must be corrected as this will cause a overheat build up of the associated wiring which will lead to other problems.
Get back to us with your findings.