Mercury 35/40HP 2 Cylinder Outboards Service Manual PN 90-42794--1, Page 369Get this manual
Horn Sounds Continuous Tone When Key Switch Is Turned "On" IMPORTANT: Make sure outboard has not overheated causing warning circuit to activate horn normally
TEST 1: Disconnect 3-pin connector from AutoBlend with key switch in "ON" position and horn soundingHorn stops soundingHorn continues to soundGo to TEST 2
Replace electronic module
Horn stops sounding
TEST 2: Disconnect all three tan (or tanblu) wires from test pOint 1Make sure disconnected wires do not touch each other or outboard ground
Horn continues to sound
Repair or replace tan or tanblu wire and temperature switch