Engine Swap 99 to 87 Merc 3.0 No power when key is "On"

KingMarine

Recruit
Joined
Jul 15, 2020
Messages
2
Hello there, long story short.. I have a 2000 party barge pontoon that the Mercruiser 3.0 had to be swapped out of. We replaced both the engine and outdrive with a functional 87 Mercruiser 3.0. The primary issue is that the engine will turn over and start while it is cranking, however it seems to lose all power when you let the key rest in the ON position? I did notice that the connectors match up but one wire is missing in one of the connectors. In preliminary pinout lookups I believe this wire is not related to power or ignition, perhaps audio warning alarm? Any help is appreciated.
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
:welcome: aboard.

If you're not losing instrument power in the ON position, then that symptom is usually an indicator that the resistance wire (in the engine harness) has failed...

Chris.........
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
51,331
use a DVM and start at the key switch and start looking where you loose voltage starting at the key switch.

I have gone thru 2 key switches on my current boat since 2011 because the "run" terminal was worn out
 

KingMarine

Recruit
Joined
Jul 15, 2020
Messages
2
Thank you for all the input. This last weekend had to work on my wife's truck. Will be back out there Saturday trying to figure out the culprit.
 
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