500 efi wiring
 

Hi we have a 1991 chaparral 2550 sx sport. This boat came with a 7.4 mercruiser engine. We have upgraded to a 500 efi. Although the engine harness and boat harness plug ins match I see they are not the same according to the schematics. the mercury service manual says that there is a plug in for the trim sender at the fuel injection harness but I have looked thru eveything and cannot find it. also we have have an alarm going off even though I have disconnected each sender one at a time and still have alarm going off. Oil presure, coolant temp and drive oil is ok. Do I need a different boat harness.

Fixx
 

i believe you need this adaptor for it to work..

http://www.michiganmotorz.com/mercru...ess-p-972.html

or mabe this one if the efi engine has a 14 pin harness..

http://cgi.ebay.com/ebaymotors/NEW-M...-/200600902112

the 500 efi has an engine oil temperature sender that our boat did not come with. according to the schematics, the wire at the boat harness use to run the trim sender but the engine harness uses the pin for the oil temp sender. I do not see where either of these harnesses would plug into.

our boat harness has 10 a pin connector

Fixx
 

the first pigtail,,you remove the one on the trim pump and that pigtail plugs in it,then the other side goes to the 3 prong weather pack on the engine..i would have to see which harness you have in order to give the rite adaptor..

the first one on my post may be the rite one or may not..


***Power Trim Adaptor Harness To convert older P/T pump with 3 blade connector to newer remote control harness with 3 pin Packard connector.