Engine Fuse Blows When Cigar Lighter Used

[bobperk]

I have a 2014 Dauntless 170 with a Mercury 90-HP engine.

When I use the cigar lighter power socket for any accessory, the 15-Ampere "Helm" fuse under the engine cowling will blow. When this happens, the engine and trim system are disabled, but the cigarette lighter plug still works. When I remove the 15-Ampere fuse and test the cigarette plug, it still shows 12 volts. The fuse does not blow immediately when I plug something in, but will blow within a few minutes, even if the accessory is unplugged. Any ideas?

[jimh]

To understand the electrical power distribution system on your 2014 Boston Whaler boat, we will need a schematic diagram of the electrical power distribution system. Do you have a pointer to such a diagram? If you do, please give us the URL for that resource so we can see it.

Was the cigar lighter power socket added by a dealer or owner of the boat after it left the Boston Whaler factory?

The branch circuit that is fused at 15-Amperes, labeled "Helm", and comes from the engine itself would be expected to only supply power to the engine controls and gauges at the helm. This circuit should not be associated with the cigar lighter socket. It usually supplies power to the ignition key and to any devices wired to the ACCY circuit of the ignition key. The ACCY circuit is usually energized when the ignition key is in the RUN position.

You report that the cigar lighter power socket still has power after the 15-Ampere engine "Helm" fuse opens--that is really odd.

Check the wiring of the cigar lighter power socket very carefully. It sounds like there is something going awry with that device. Verify the actual power source for the cigar lighter power socket. It should have its own branch circuit and not be wired into the helm ignition key ACCY circuit.

[jimh]

The fuse does not blow immediately when I plug something in, but will blow within a few minutes, even if the accessory is unplugged.

I don't think you've established that the actual cause of the fuse blowing is from insertion of some accessory into the cigar lighter power socket. Are you certain the engine 15-Ampere fuse only opens when something is plugged into the power socket? You may have just observed a coincidence in this happening, and the true cause of the fuse blowing is something else.

[bobperk]

The fuse [under the engine cowling which is a 15-Ampere rating and is marked "helm"] has blown three times since I bought this (new) boat two years ago. Every time [the fuse under the engine cowling] blew was on a day that I used a portable bait tank with a plug-in aerator. [The fuse under the engine cowling] does not blow when I first plug in [the aerator for the portable bait tank], and when [the fuse under the engine cowling] did blow, the plug [from the aerator for the portable bait tank] had been unplugged. [The fuse under the engine cowling] appears weakened, and then when I try to start the engine or tilt the motor [the fuse under the engine cowling] fails. I have never used any other plug-in accessory and I have never blown this fuse outside of the three occasions mentioned.

[jimh]

If the circuitry is intact, there should be no association between the cigar lighter plug and the engine's 15-Ampere fuse under the engine cowling. Look for something that has been mis-wired or circuits that have come in contact accidentally. There is no way to resolve this without you carefully inspecting and examining all the circuits involved.

[macfam]

See folios marked 4.7 and 4.8 [pages 83 and 84 of the PDF]:

http://bostonwhaler.com.s3.amazonaws.com/resources/170-Dauntless-Owners-Manual-2014.pdf

[jimh]

Try this test: remove the fuse for the cigar lighter power socket at the dash area--not the one you refer to as "HELM" and say is under the cowling, but the one it is supposed to be wired to according to the wiring diagram that another reader researched and kindly posted the URL to it for you.

If the cigar lighter power socket is wired properly, there should be no power there when you remove that fuse. If after pulling the fuse for the cigar lighter power socket, there is still power at that socket, then there is something really haywire.

[jimh]

By the way, if you are the original owner and the boat was purchased new only two years ago, I would just call the Boston Whaler dealer and ask him to fix this problem. Boston Whaler boats are not supposed to have mysterious electrical problems where fuses in their Mercury engines fault open because an accessory is plugged into a cigar lighter power socket on the dashboard. If this is all OEM gear, seek help from the dealer under the terms of the warranty on the boat.

If they tell you that failure of the engine electrical wiring or the dashboard wiring is not covered under the Boston Whaler warranty or the coverage has elapsed, tell them that's not the deal you understood when you paid for a premium quality Boston Whaler boat.

Really, if nothing has been screwed-around with in the boat's wiring, this should not be happening and you shouldn't have to fix it on a two-year-old boat that cost you probably $40,000.

[jimh]

Here is a big hint for you about where to look for haywire. This is what I would look at first:

Since MacFarm was kind and researched the schematic diagram and gave the URL for it, look at the wiring diagram. There is a multi-contact plug-socket connector system that connects the wiring harness at the dashboard to the wiring harness from the stern of the boat. Locate this connection point.

Carefully examine the connections and wires on each side of this connection. Note the very interesting close proximity of these two circuits:

CIRCUIT 510, a RED 14-AWG conductor is on pin "S"

CIRCUIT 803C, a VIOLET (that's purple for our younger readers) 16-AWG conductor is on adjacent pin "T"

Quite interestingly, the RED conductor is associated with the cigar lighter power socket 12-Volt power. And the VIOLET conductor is associated with the engine 12-Volt power.

Make a very careful visual inspection of the two connectors. Verify that the proper conductor is in place in each connector, that is, the positions are not swapped on one side of the connection. Also, using very good lighting and a magnifying glass, examine the conductors and the connector contacts to make sure there is not some sort of a stray whisker of a wire that is connecting these circuits together.

The notion that they seem to interact and that they are carried on adjacent pins of the connector has got to be more than just coincidence.

[mag]

Several years ago I had a puzzling problem that might be similar to yours. I had a switch (mine was a float switch to the bilge pump) wired directly (thru a fuse) to one of my two batteries and the bilge pump was also wired thru to a toggle switch on the dash (powered via the battery A/B switch). Whenever the float switch actuated at the same time as the dash toggle switch while the A/B switch was on the “other battery”, there was direct short across the two + sides of the batteries. If the engine was running and charging one of the batteries at 14+ volts, then the ~1.5 volt short across the fuse would cause it to blow. Long story short, if you have two batteries and an A/B battery switch, you might want to check to see if your lighter is wired to both the A/B switch and also directly to one of the batteries. Hope that is some help. -Mike

[bobperk]

Thanks to all for the advice. I will work on these tests and get back.

Unfortunately for me, I added an hour meter, GPS, Bow mounted trolling motor, second battery and battery switch to this boat. So the warranty may not be an option for me unless I can verify the problem is not related to something I did.

[jimh]

...I added...second battery and battery switch to this boat. So the warranty may not be an option for me unless I can verify the problem is not related to something I did.

Owner-added electrical gear and wiring could be related to this problem. Sometimes electricity will follow a "sneak circuit" that is not obvious to a human. We expect things to work the way we expect them to work, but electricity just flows where its conductors allow it to flow.

Did the problem with the fuse ever occur BEFORE you made changes to the boat's factory wiring?