Fire sinks our beloved ship

[Bob Ohler]

In point #9, from Westerbeke why do we use "wire length round trip?" The cable is only going from point A to point B... right?

[Maine Sail]

In point #9, from Westerbeke why do we use "wire length round trip?" The cable is only going from point A to point B... right?

Bob,

All DC circuits are a loop. They leave on battery + and return on battery neg. You need to count both the supply and return lengths of neg and pos wires for total circuit length..

So if it is 6 feet if wire length, not as the crow flies but length along the wire, to the starter, then it's most likely 6 feet of neg wire back to the battery. That circuit is 12' round trip...

[Mathias]

This fuse is big news. It means I will be able to sleep again on a boat.

The first couple of weeks, I had nightmares of being on a boat and not being able to sleep because I kept smelling smoke.

Thanks for the link,
-Mathias

[Maine Sail]

This fuse is big news. It means I will be able to sleep again on a boat.

The first couple of weeks, I had nightmares of being on a boat and not being able to sleep because I kept smelling smoke.

Thanks for the link,
-Mathias

They can help create piece of mind..

[Sea Hunt Video]

Assuming I understand 10%-15% of this discussion, I am ordering two (2) Blue Sea MRBF fuses for S/V Bali Ha'i.

I have two Group 27 batteries that are standard for a Cape Dory 25D. They are NOT connected in parallel except from the battery switch on the electrical panel. The negative terminals (-) of each Group 27 battery are connected together and then connected to the engine block.

I plan to install (with the assistance of an ABYC certified electrician) two (2) Blue Sea MRBF fuses - one on each battery post (+) terminal.

Am I sort of in the ballpark of "doing it right"

[Maine Sail]

Assuming I understand 10%-15% of this discussion, I am ordering two (2) Blue Sea MRBF fuses for S/V Bali Ha'i.

I have two Group 27 batteries that are standard for a Cape Dory 25D. They are NOT connected in parallel except from the battery switch on the electrical panel. The negative terminals (-) of each Group 27 battery are connected together and then connected to the engine block.

I plan to install (with the assistance of an ABYC certified electrician) two (2) Blue Sea MRBF fuses - one on each battery post (+) terminal.

Am I sort of in the ballpark of "doing it right"

Yes you're on the right path but you don't really need an electrician if you don't want one. Installing an MRBF is fairly straight forward stuff. If you let me know your engine model and battery cable size I can tell you the size fuses that could be used. MRBF's are available up to 300A, which is usually bigger than is needed on small aux engines.

[Steve Laume]

Robert, you are a man of action. It sounds like you now have your certified electrician on line and I am sure you can handle the four nut installation.

Once again I am impressed by our message board and the people who use it, Steve.

[Sea Hunt Video]

If you let me know your engine model and battery cable size I can tell you the size fuses that could be used. MRBF's are available up to 300A, which is usually bigger than is needed on small aux engines.

Thanks, Maine Sail. I will get you that info tomorrow. The engine is the original Yanmar 1GM (1982). The batteries are AC Delco Voyager Group 27. I think you had told me in an earlier thread that the load test amps rating was 270 but the normal rating capacity was 105 amps.

I am not sure of the battery cable size. I know I increased the gauge but not sure exactly what it is now. I will read it off the cable tomorrow.

On Battery #2 (the house battery) I installed the bilge pump wire directly, by-passing the electrical panel. Would you recommend that I install the MRBF Terminal Fuse Block with two posts (PN 2151) and attach the bilge pump wire to the "inside" post (the one closet to the battery post) Or use PN 5191 and attach the bilge wire onto the same battery post as the battery cable wire

[Maine Sail]

If you let me know your engine model and battery cable size I can tell you the size fuses that could be used. MRBF's are available up to 300A, which is usually bigger than is needed on small aux engines.

Thanks, Maine Sail. I will get you that info tomorrow. The engine is the original Yanmar 1GM (1982). The batteries are AC Delco Voyager Group 27. I think you had told me in an earlier thread that the load test amps rating was 270 but the normal rating capacity was 105 amps.

I am not sure of the battery cable size. I know I increased the gauge but not sure exactly what it is now. I will read it off the cable tomorrow.

On Battery #2 (the house battery) I installed the bilge pump wire directly, by-passing the electrical panel. Would you recommend that I install the MRBF Terminal Fuse Block with two posts (PN 2151) and attach the bilge pump wire to the "inside" post (the one closet to the battery post) Or use PN 5191 and attach the bilge wire onto the same battery post as the battery cable wire

Just go with an in-line fuse, ATC type, for the bilge pump. MRBF's are too big for that, smallest is 30A, and you don't need to spend that kind of money to protect the small bilge pump wire..

These are the ATC in-line holders I use. They are the two small read wires coming off the + post. On this boat one was for the VHF and one was for the bilge pump. Due to height restrictions I used ANL fuse blocks instead of MRBF's....


Your fuse size will be determined by the battery cable as your motor draws very little starting current.

This is the ABYC max ampacity chart for non-bundled wire. You need to know the jackets temp rating and teh gauge of the wire.

For example if you have 2GA wire the biggest fuse you can use is 210A at 100% of the rating for 105C jacketed wire.

However, if needed, you can go to a max or 150% of this tables rating so even a 300A fuse can work, on 2GA wire, if not inside an engine space. If much of it is inside an engine space it would get derated..

[mahalocd36]

MaineSail, your contributions to this board are invaluable.

We are going to add the fuses to Mahalo before next sailing season.

Thanks!

[Bob Ohler]

MS,

I was looking at the MRBF's at West Marine today. With the additional added height of the Blue Sea MRBF, it would be impossible to get the cover(s) back on my battery boxes. Could the MRBF's be mounted outside the boxes but in close proximity to the boxes? How would you do this?

[Maine_Buzzard]

You'd be better off mounting a typical ANL fuse, in a block with a cover. The MRBFs lack one stud for mounting.

Cost is the same, about 18 for the holder and 16 for a fuse.

Blue Seas make a MEGA fuse that will work too, but why lock yourself into a sole sourced part.

A protective cover is included on the ANL, you'd need to enclose a MRBF

[Maine Sail]

MS,

I was looking at the MRBF's at West Marine today. With the additional added height of the Blue Sea MRBF, it would be impossible to get the cover(s) back on my battery boxes. Could the MRBF's be mounted outside the boxes but in close proximity to the boxes? How would you do this?

Best to use an ANL of not mounting direct to the post. You could also use a Class T fuse but they are more $$.

Blue Sea ANL Fuses:
http://bluesea.com/category/81/22/produ ... erview/135

Blue Sea ANL Fuse Holder (5005 is what you want):
http://bluesea.com/category/81/21/productline/129

We have five ANL's on our boat. House bank, start bank, inverter feed, battery charger & alternator.

[Sea Hunt Video]

If you let me know your engine model and battery cable size I can tell you the size fuses that could be used. MRBF's are available up to 300A, which is usually bigger than is needed on small aux engines.

Maine Sail:

Sorry for the delay in getting you the information. Yesterday I was presented with a "Honey Do" list the likes of which I have not seen in years.

As I had said in an earlier post, the engine is a Yanmar 1982 1GM (7.5 hp). The starting motor is a 12V-1.0kW. The alternator (newer model) is a 12V-35A.

It was a little difficult to read the labeling on the battery wires. Here is what I have (I think):

PACER 2 AWG 600V UL OIL RESISTENT TEW 105 C.

I specifically requested 2 AWG sizing for the battery cables. This made it difficult to connect the battery cables to the electrical panel, etc. but I thought the increased size would be beneficial. I was probably wrong and it was unnecessary. But..... it is done.

In looking at the chart you posted it looks like a 201A fuse would be the correct size. Am I at least close to the correct answer

In studying the batteries and battery boxes today, I am in agreement with Bob Ohler. The MRBF's are probably "too tall" for the battery boxes and will prevent the boxes from completely encapsulating the batteries.

The ANL fuses/blocks may be a better choice. However, being the dummy that I am, I am not sure of exactly where/how I would install these fuse blocks. Looking at the blocks, it seems like they would not attach to the battery terminal.

Where would one (someone who is not a dummy like me ) install the ANL fuses and fuse block units

[Sea Hunt Video]

If you let me know your engine model and battery cable size I can tell you the size fuses that could be used.