M25XPB eng/battery fuse size

[Clydo]

There are two flat fuses bolted to "floor" of battery compartment. Battery
cables red one connected to each end of both fuses. Located next
to batteries. Ends of one of mine are corraded and need to be replaced.
Guy doing work said he thinks he can read 150 amps on them but
not sure.

Catalina factory can't give me answer. Appreciate any suggestions.

Clyde Thorington
C310 # 245
ILEAN TOO
San Jose, CA

 

[Richard19068]

I don't have an answer but might suggest that the "guy doing work" should have a pretty good idea of what you should have.

Here is some good info from Marine How To:

Bare Minimum Fuse Sizes
Let’s cut-to-the-chase on this. Below are the minimum bank fusing we prefer to see for any bank that could ever be called upon to start a motor. If your vessel has a 1/2/B switch both banks need to be capable of starting the engine.
Bare minimum fuse size for small diesel engines 8HP to 25HP = 250A
Bare minimum fuse size for medium diesel engines 25HP to 60HP = 300A
Above 60HP 75% of measured *inrush current as minimum fuse size.
*You will need a clamp meter such as a Fluke 376, or equivalent, to measure the inrush.
If you follow the above guidelines, you will not suffer “nuisance trips” if fusing your starting bank.
If your engine is too large for a fuse put the entire length of the cranking conductor in a protective conduit or protective loom! Unprotected battery cables are a fire waiting to happen!

Selecting the Proper Type of Fuse:
Battery banks larger than 255Ah should be protected with fuses not breakers. The following types of fuses are suitable for main bank protection:
ANL


CLASS T (preferred for Li-ion& large AGM Banks)


MRBF

These fuses are available from Blue Sea Systems and other reputable sellers. They should however be “Ignition Protected” fuses if installed on a gasoline boat and Blue Sea Systems is the only one I know of offering ANL fuses with ignition or spark protection for ANL’s. Class T fuses are not technically IP rated however they are fully encased in a metal body. Class T fuses have simply not been tested for IP rather than do not meet IP. In speaking with Blue Sea systems I was told they have no documented cases of an IP breach on any Class T fuses.
Remember, the main battery over current protection (OCP) or over current protection device (OCPD) is sized to protect the wire. The main bank fuse is not there to protect the down-stream equipment. Those fuses would be located after the main bank protection fuse. This is often misunderstood.
You can always go smaller with OCP than the wires ampacity rating, but ideally should not exceed the ampacity rating unless you are fusing the battery bank and the bank could potentially be called upon to crank a motor. The main bank fuses are there to prevent the wire from overheating, melting and starting a fire in a dead short situation. Generally speaking a fuse is sized to not exceed the maximum ampacity of the wire. In certain instances the ABYC allows for up to 150% of the chart below.

Battery Banks & Over Current Protection - Marine How To

Battery Banks & Over-Current Protection A 300A (MRBF)Battery Terminal Mounted Fuse by Blue Sea Systems In this article we will discuss fuse selection, fuse types, wire ampacity, Amperage Interrupt Capacity (AIC) and even potentially unsafe ABYC “exceptions to the rules”. In short,

marinehowto.com

 

[Stu Jackson]

Battery
cables red one connected to each end of both fuses. Located next
to batteries.

Clyde,

I assume you mean: Battery cables red, one connected to each end of both fuses. Located next
to batteries. [I added the comma]

C'mon, you've been around here long enough to know that our first question HAS TO BE: what is at the other end of the wires? And what size are the wires? would also help.

 

[jssailem]

Clyde
I had to redo my cables and fuses after the inundation of water in the boat occurred last August. The water reached the wiring on the engine. The fuses blew. When the batteries went under there must have been all sorts of mayhem.


I rebuilt with the same 300 amp MRBF fuses on the batteries to protect the wires running to the engine starter and the ACR for the starter battery (the ACR and starter battery were saved being located above the level of the inundation).

I have a 47HP engine. When using a 150 fuse on the starter, the fuse would blow every second or third start. After 2 failures, I upped to MaineSail’s recommended 300 amp fuse and no further problems. I noted that the original configuration when I purchased the boat did not have a fuse between the batteries and the starter motor. That was old school thinking.

 

[Tom J]

Clyde, I seem to remember the ANL fuses being 150 amp rating. One of them blew when the stater motor shorted one time, and I replaced it with the same rating. I never had a problem with a fuse blowing while starting the engine, etc. I figured if the 150 amp fuse is good enough for the factory, it's good enough for me.

 

[Clydo]

I don't have an answer but might suggest that the "guy doing work" should have a pretty good idea of what you should have.

Here is some good info from Marine How To:

Bare Minimum Fuse Sizes
Let’s cut-to-the-chase on this. Below are the minimum bank fusing we prefer to see for any bank that could ever be called upon to start a motor. If your vessel has a 1/2/B switch both banks need to be capable of starting the engine.
Bare minimum fuse size for small diesel engines 8HP to 25HP = 250A
Bare minimum fuse size for medium diesel engines 25HP to 60HP = 300A
Above 60HP 75% of measured *inrush current as minimum fuse size.
*You will need a clamp meter such as a Fluke 376, or equivalent, to measure the inrush.
If you follow the above guidelines, you will not suffer “nuisance trips” if fusing your starting bank.
If your engine is too large for a fuse put the entire length of the cranking conductor in a protective conduit or protective loom! Unprotected battery cables are a fire waiting to happen!

Selecting the Proper Type of Fuse:
Battery banks larger than 255Ah should be protected with fuses not breakers. The following types of fuses are suitable for main bank protection:
ANL


CLASS T (preferred for Li-ion& large AGM Banks)


MRBF

These fuses are available from Blue Sea Systems and other reputable sellers. They should however be “Ignition Protected” fuses if installed on a gasoline boat and Blue Sea Systems is the only one I know of offering ANL fuses with ignition or spark protection for ANL’s. Class T fuses are not technically IP rated however they are fully encased in a metal body. Class T fuses have simply not been tested for IP rather than do not meet IP. In speaking with Blue Sea systems I was told they have no documented cases of an IP breach on any Class T fuses.
Remember, the main battery over current protection (OCP) or over current protection device (OCPD) is sized to protect the wire. The main bank fuse is not there to protect the down-stream equipment. Those fuses would be located after the main bank protection fuse. This is often misunderstood.
You can always go smaller with OCP than the wires ampacity rating, but ideally should not exceed the ampacity rating unless you are fusing the battery bank and the bank could potentially be called upon to crank a motor. The main bank fuses are there to prevent the wire from overheating, melting and starting a fire in a dead short situation. Generally speaking a fuse is sized to not exceed the maximum ampacity of the wire. In certain instances the ABYC allows for up to 150% of the chart below.

Battery Banks & Over Current Protection - Marine How To

Battery Banks & Over-Current Protection A 300A (MRBF)Battery Terminal Mounted Fuse by Blue Sea Systems In this article we will discuss fuse selection, fuse types, wire ampacity, Amperage Interrupt Capacity (AIC) and even potentially unsafe ABYC “exceptions to the rules”. In short,

marinehowto.com

Thank you very much for all the information you provided. Very clear. Appreciate the time you
spent putting this together.

Clyde Thorington
C310
ILEAN TOO
San Jose, CA

 

[Clydo]

Clyde, I seem to remember the ANL fuses being 150 amp rating. One of them blew when the stater motor shorted one time, and I replaced it with the same rating. I never had a problem with a fuse blowing while starting the engine, etc. I figured if the 150 amp fuse is good enough for the factory, it's good enough for me.

Tom thank you. Have had boat for eleven years and fuse size worked for me. My boat has electric windless
and never had fuse failure during use. Think that must be original factory fuse size. This is the information
I was looking for. Thanks again.

Clyde Thorington
C310 # 245
I LEAN TOO
San Jose, CA

 

[Clydo]

Clyde,

I assume you mean: Battery cables red, one connected to each end of both fuses. Located next
to batteries. [I added the comma]

C'mon, you've been around here long enough to know that our first question HAS TO BE: what is at the other end of the wires? And what size are the wires? would also help.

Stu you are so right. After 20 plus years of Q & A on C27 - C30 - and now C31 I should know proper info
to provide to help get good information. I should have started by saying am looking for exact
replacement size and not info to establish proper fuse size. Current fuse size has worked
fine for over eleven years I have had boat . I had thought posting on list with other owners
of exact boat someone would - after looking in their own - boat provide fuse size for replacement since guy doing
work on my boat couldn't read number on fuse due to corrasion.
Mei Culpa Mei Culpa

Clyde Thorington
C310 # 245
I LEAN TOO
San Jose, CA

 

[Tom J]

Tom thank you. Have had boat for eleven years and fuse size worked for me. My boat has electric windless
and never had fuse failure during use. Think that must be original factory fuse size. This is the information
I was looking for. Thanks again.

Clyde Thorington
C310 # 245
I LEAN TOO
San Jose, CA

I looked at the owner's manual and the DC circuit schematic doesn't even show the fuses. No wonder the factory couldn't help you. Like you said, though, I had my boat for 17 years, and the stock fuses seemed fine. I wish I still had my boat so that I could double check my memory.

 

[Tom J]

I looked at the owner's manual and the DC circuit schematic doesn't even show the fuses. No wonder the factory couldn't help you. Like you said, though, I had my boat for 17 years, and the stock fuses seemed fine. I wish I still had my boat so that I could double check my memory.

I found this pic in my photo archives. Looks like my ANL fuses are actually 130A, so the 150's should b fine.

 

[Clydo]

Clyde
I had to redo my cables and fuses after the inundation of water in the boat occurred last August. The water reached the wiring on the engine. The fuses blew. When the batteries went under there must have been all sorts of mayhem.
View attachment 223757 View attachment 223758

I rebuilt with the same 300 amp MRBF fuses on the batteries to protect the wires running to the engine starter and the ACR for the starter battery (the ACR and starter battery were saved being located above the level of the inundation).

I have a 47HP engine. When using a 150 fuse on the starter, the fuse would blow every second or third start. After 2 failures, I upped to MaineSail’s recommended 300 amp fuse and no further problems. I noted that the original configuration when I purchased the boat did not have a fuse between the batteries and the starter motor. That was old school thinking.

Some one found owners manual for our Maxwell electric windless.
12 volt Normal working load 80-120 AMP
12 volt At stall 305 Amps

Page 3 in the manual

Clyde Thorington
C310 # 245
ILEAN TOO
San Jose, CA

 

[jssailem]

12 volt Normal working load 80-120 AMP
12 volt At stall 305 Amps

Most boaters will head to the nearest marine store and grab a fuse they saw on their boat before, or take the word of the shop clerk that most boaters use these fuses.

There is a lot of science that goes into a fuse. Choosing the right one can be a selection based on knowledge or grab one and try it. If it works it must be ok.

Your manual says in a stall there could be a current overload condition. This would indicate that you need to consider this issue when selecting the sizes of your wires and the fuses used to protect those wires. In a stall you might want to have enough time to shut down the windlass or maybe you want the fuse to shut it down for you.

FUSE CHARACTERISTICS: This characteristic of a fuse design refers to how rapidly it responds to various current overloads. Fuse characteristics can be classified into three general categories: very fast-acting, fast-acting, or Slo-Blo® Fuse. The distinguishing feature of Slo-Blo® fuses is that these fuses have additional thermal inertia designed to tolerate normal initial or start-up overload pulses.​

It is more convenient to avoid Nuisance openings than constantly replacing underrated fuses.

NUISANCE OPENING: Nuisance opening is most often caused by an incomplete analysis of the circuit under consideration.​

An in depth review of fuses can be found here.

https://www.tti.com/content/dam/ttiinc/manufacturers/littelfuse/doc/littelfuse-fuseology-selection-guide.pdf

 

[Clydo]

I found this pic in my photo archives. Looks like my ANL fuses are actually 130A, so the 150's should b fine.
View attachment 223794

Great picture nice clean looking installation. Four batteries easier
to handle. Easy to read fuse number. Thank you for sending.

Clyde Thorington
C310 # 245
I LEAN TOO
San Jose, CA