This summer Bill of Rhapsody and I had a discussion going about the Master Fuse for the fuse panel and the "Motor Fuse" that shows up on the wiring diagram for the Yanmar. Today I was doing some of my once every 25 year maintenance and looked for the Motor Fuse.

On the 500 series boats it is located directly behind and under the air cleaner, in a GREEN fuse holder, black taped to the wiring harness, red leads spray painted mostly motor gray. Hopefully they didn't tape it more than they have on Vee Jay. [You have to take the air cleaner off to access it]

So if some day you turn the ignition on, and the oil alarm doesn't sound, and the motor doesn't turn, but your radio still works ... it may be just possible that this fuse popped or the fuse holder cracked.

I thought it looked good enough not to have to do a close inspection and take it apart at this 25 year check up ... will look at it again in 10 years.

A different scenario on Rhapsody. There is a 30 amp inline fuse going to the DC power panel that was installed directly behind the battery disconnect switch. This is in addition to the fuse Vic describes which is shown on last page of the Yanmar Operation Manual. The fuse for the Yanmar is only for the starting solenoid, idiot lights and alarm. DC power for the starter is connected directly from the battery switch with the heavy gauge battery cable.

I was delivering the boat to be hauled for the season a couple years back and found that nothing worked electrically, except for the engine panel. It turns out that the hidden fuse socket behind the battery disconnect switch that feeds the DC power panel had corroded terminals causing a high resistance connection. The high resistance connection heated up and melted the insulation on the wire by the fuse socket. So I recommend that people check to see if you have an inline fuse similar to what Rhapsody has. I've replaced it with a spray tight inline socket, and sprayed WD40 on the terminals before installing the fuse. Moral of the story - look to see if you have a hidden fuse like this before it causes a problem.

By the way - I uploaded all the Yanmar reference material to the J/30 Class website. Go to the J/30 home page, then from the top menu mouse over "Info", "Articles of Interest", and click on "Diesel Engine Maintenance"

While we are on the master fuse/panel wiring topic:

This has happened to me twice: I have all the halogen cabin lights running, I'm washing dishes so the water pump is running.

My lights flicker a bit with the running water pump, then I either:

1) blow the fuse that Bill is talking about
2) completely melt down the fuse holder Bill is talking about, thus losing power altogether

I replaced the fuse and holder with a big 30A heavy-duty holder and fuse, but I wonder:

-if maybe my water pump is pulling too much amperage

-or maybe the house panel master wire is too small

-or maybe the boat didnt come with halogen bulbs originally which is why it cant handle all that power

or maybe all of the above!

Anyone seen similar issues?

-dan

Dan - some follow up questions..

• Have you had the problem since replacing the fuse and socket? If not, problem solved.
• Do you know the draw on the Halogen lamps? I think they are 20 Watts which equates to 1.7 amps each. If so, there are 8 lights in the cabin on Rhapsody, so that's 13.6 amps just for lighting.
• What kind of pump/motor is it, and is there a label listing current drain? I suspect it has a high current draw since the lights flicker, or you have a high resistance connection in the supply or return circuit between the DC power panel and the battery. (e.g. bad contacts on the switch, corroded terminals, poor fuse connections, wire has degraded over time in marine environment)
• Rhapsody has manual pumps in the water system, so no electrical issues.

I know my Nav lights eat up battery. When delivering Rhapsody back from Westport, I ran the nav lights for 4 hours on one battery, then had to put the battery switch on "All" to start the Yanmar and charge the battery.

I'll be at the boat this weekend and I will check the details.

I have not burned out another fuse/holder, but the lights still fluctuate quite a bit when the water runs, making me think I might be walking on a crutch right now...

-dan

When Bill told me last summer that little fuse holder hanging off the battery switch was the master fuse for the fuse panel it astounded me. It was basically a 20 amp fuse holder with what looked like a #14 wire that came off the battery switch and then was connected to a #10 wire to run to the fuse panel.

Over the years I had worked around it running separate leads for my ham radio equipment directly off the battery.

Last year I added a second #10 red and black line to the fuse panel from a third battery that i keep in the plastic settee bin aft of the fuel tank. the red goes to the load side of one of the auxiliary switch and fuse holders on the main fuse panel and through that fuse and on/off switch to the main + buss at the fuse panel. The black just goes to the main black buss screwed on the hull. This way I can switch the spare battery in when I need it. For sailing/racing/overnights we turn the main battery switch to off and click on the third battery for lights, GPS and radio ... and run it to useless. Then switch it off and put one of the main batteries on.

I used to use a #27 battery and that would last most of the night, but that is too heavy for me now. The smaller #24 battery is no where near as good.

This year I changed the original fuse holder at the battery switch to an ATC 30 amp blade holder as I was having low voltage warnings at the GPS. That didn't help ... so I ran another set of Red and Black directly from engine to the master fuse panel...I now have three sets of #10 wires feeding the master fuse panel.

I am still experimenting to get the voltage at the GPS stronger for a longer time. But three batteries is nice if you want to gobble up amps.

The line from the engine as well as the one from the battery switch have 15 amp ATC fuses which I think will both blow if I get up over 30 amps. When you start to add up amps for gps, instruments, auto helm, radio and a few lights, bilge pump, fresh water pump, CD player you can start to chew up amp hours. and as I remember these Dual Purpose batteries have just about 120 hours ... but the voltage drops continually during that time.

Surprisingly we can charge the spare battery by leaving it on when the motor is running and have not yet blown out a fuse. And if the starting battery is a little weak clicking on the fully charged spare battery easily helps start the motor.

The line from the spare battery has a 20 amp glass fuse it goes through at the master panel.

All that said there are different water pressure pumps available and you are better off with the smallest one available, which I think is a 1.9 gal flow.

Follow up on prior posts.
1.If you do attach a backup battery ala Vee Jay don't try to use it to start the engine by itself ... that will blow out the master 30 amp fuse for the fuse panel. (Inquiring minds want to know this stuff.) This "spare" battery is basically our night run battery to reserve the house batteries.
2. The Green Motor Fuse holder talked about in the original note that started this thread has a spare fuse inside the fuse holder. I rethought out the wait of ten years to check this fuse next ... the existing motor fuse and spare looked new after 25 years.

I found out this fuse existed on an overnight to Booth Bay Maine about 2am all electric shut off. It was blowing 20+ and we were screaming at about 10+ downwind wing on wing having a blast, until then. I could not for the life of me find what the issue was but I figured it must be a ground or something since everything went out at once. We could also still start the motor so I was not to worried, just curious what the issue was. It turned out to be the fuse holder came a part. I looked at it 10 times that night but thought it was to the flexible solar panel that the boat came with so I did not put it back together. I just never thought a 5A (yes mine was a small fuse) fuse would be in-line with the whole fuse panel.

Luckly I carry a battery gps and handheld VHF so we were safe accept for the running lights but I also have a battery powered spot light that we hit the sails with if we saw a fishing boat.

I replaced with a 30A blade type of fuse, but still wondered why the fuse panel was fused??? Sounds like no-one is quite sure.