Mercury 35/40HP 2 Cylinder Outboards Service Manual PN 90-42794--1, Page 343Get this manual
Horn Does Not Sound When AutoBlend Is Turned Upside Down
TEST 1: Disconnect wiring harness from warning horn connector and check for presence of battery voltage (9V DC minimum) between pin #1 and pin #2
Battery voltage not present
Battery voltage present.l Go to TEST 2
Refer togeneral checksand check items thru 5TEST 2: Disconnect 2-pin connector from tank receptacle and install jumper wire between pinsHorn does not soundI
Horn soundsGo to TEST 3- 1