Loss of Electrical Power to Engine

[macfam]

[This thread is moved to SMALL BOAT ELECTRICAL for discussion]

My 2005 170 Montauk with 2005 Mercury 90 FOURSTROKE has no electrical power. The boat has a freshly charged battery. The terminals [of some unspecified connection point] are clean and tightened by wrench. There is no power-trim operation. The engine does not crank over; the engine shut-off safety lanyard is in place; the remote shift control is in the NEUTRAL position.

However, the boat's navigation lamps, boat whistle (horn), and sump pump work properly.

My deduction is the [electrical] connection [from the battery] to the engine is the cause of this problem.


Q1: is there a fuse located somewhere that needs to be checked?

[Phil T]

Is the wheel turned to one side? Move to pointing straightahead. There was a problem of a pinching of the harnesses at full lock. Attempt start.

Remove and check the fuses under the cowl of the engine. Replace them.

Do you have a main battery switch? Rotate on/off several times.

Check the main reset breaker in the console. Does it reset?

Report back answers and what specifically you have checked.

Do you accessories work? Bilge?

[jimh]

Most ALL outboard engines have a fuse located under the engine cowling that protects the branch circuit from the unfused BATTERY positive connection under the cowling to the helm ignition switch. This fuse is typically a 10-Ampere rated fuse. This fuse is likely the cause of the symptoms you report.

I recommend:

• Remove the engine cowling.
• Make a close visual inspection for a fuse holder in the engine wiring harness.

The fuse is associated with the ACCY (accessory) circuit. This fuse protects the wiring to the helm ignition key switch. If this fuse is blown, then the symptoms you describe will occur.

If you plan to perform work or diagnostic tests on your outboard engine, you should purchase the factory service manual for the engine. The factory service manual for the engine will contain a detailed schematic or pictorial wiring diagram of all engine electrical circuits. The factory service manual will also typically contain photographic illustrations or drawings that will help you locate important electrical components on the engine. The fuses on the engine may be located behind a plastic cover that is marked FUSES. The fuse may be an ATC type fuse. The engine may incorporate an ATC fuse puller.

READ these archived articles:

Mercury 90-HP FOURSTROKE Blows Main 20-ampere Fuse
https://continuouswave.com/ubb/Forum6/HTML/002656.html

Trim-Tilt Operation Blows Fuse When Ignition Switch is OFF
https://continuouswave.com/ubb/Forum6/HTML/002762.html

Note that in c.2005 an engine labeled as a Mercury 90 FOURSTROKE could use a power head that was manufactured by Yamaha.

[macfam]

Thanks jimh and PhilT.

Sure enough, a fuse under the cowling was blown. I popped-in a new fuse, and all was fine.