$150 and a Wallyworld cutting board

[OverEasy]

Hi TheLandLady!

In my engineering practice I have always made sure that every circuit is protected.
The relevant ABYC recommendation is that there be a fuse or circuit breaker within 7” of the positive battery terminal.
There are good, reasonable a well thought out reasons for that recommendation.
Generally as a result of investigations into incidents of harm and injury.

Getting away with something isn’t the same as doing it right.

The couple of bucks to get several battery terminal fuses (one for each battery and spares) is a small inconvenience vs dealing with an electrical short out on the water in a plastic boat carrying several gallons of fuel aboard.

One will not have the time nor the means to adequately handle a wiring short circuit below deck, behind panels or in all the other inaccessible locations were wiring is routed.

The wiring cables between the battery/“Perko” switch and the engine typically is routed under the interior cabin floor in the bilge areas under the aft berth on MacGregors. These areas are not readily accessed nor are they readily inspected. Water ingress, wires sitting in water, wires moving back/forth, chaffing of insulation are common. The use of non marine grade wire and insulations appropriate for resisting fuel, oil, water, salt are also unfortunately common. These aspects can/do lead to compromised wiring and potential short circuits.

A properly wired cabling to your engine WITH a properly sized fuse or circuit breaker is the only appropriate approach to protect your boat and those on board.

Unfortunately there are not firm specific legal code requirements like there are for residential and industrial facilities, but that does not replace the need to do what is right.

It’s your boat and I can only recommend and implore to have individuals to do what it takes to do what is appropriate.
My professional career has unfortunately caused me to deal with the avoidable aftermaths of things not done to code of best practices by others.

Best Regards,
Over Easy

[TheLandlady]

Hi TheLandLady!

In my engineering practice I have always made sure that every circuit is protected.
The relevant ABYC recommendation is that there be a fuse or circuit breaker within 7” of the positive battery terminal.
There are good, reasonable a well thought out reasons for that recommendation.
Generally as a result of investigations into incidents of harm and injury.

Getting away with something isn’t the same as doing it right.

The couple of bucks to get several battery terminal fuses (one for each battery and spares) is a small inconvenience vs dealing with an electrical short out on the water in a plastic boat carrying several gallons of fuel aboard.

One will not have the time nor the means to adequately handle a wiring short circuit below deck, behind panels or in all the other inaccessible locations were wiring is routed.

The wiring cables between the battery/“Perko” switch and the engine typically is routed under the interior cabin floor in the bilge areas under the aft berth on MacGregors. These areas are not readily accessed nor are they readily inspected. Water ingress, wires sitting in water, wires moving back/forth, chaffing of insulation are common. The use of non marine grade wire and insulations appropriate for resisting fuel, oil, water, salt are also unfortunately common. These aspects can/do lead to compromised wiring and potential short circuits.

A properly wired cabling to your engine WITH a properly sized fuse or circuit breaker is the only appropriate approach to protect your boat and those on board.

Unfortunately there are not firm specific legal code requirements like there are for residential and industrial facilities, but that does not replace the need to do what is right.

It’s your boat and I can only recommend and implore to have individuals to do what it takes to do what is appropriate.
My professional career has unfortunately caused me to deal with the avoidable aftermaths of things not done to code of best practices by others.

Best Regards,
Over Easy

I don’t want to burn my boat down.
I’m plannihg to put a 50a or 100a terminal fuse on the house battery, but I’m not sure about the crank battery.
The only thing I’m hung up on is fusing the crank battery to the starter. I don’t understand the arguments against doing it, but I know people say to not do it for various reasons. People also say to do it for various reasons. I’m also hesitant to put a fuse on there after hearing that ABYC specifically says that it doesn’t need a fuse, but then again the ABYC doesn’t really take a side for or against either option.

I guess my question is: how much does my starter draw? Or how much fuse will protect against a dead short and also allow me to start a 2008 merc 2stroke 50? I’m sure starter draw is variable depending on how cold the engine is. I’ve seen threads on other forums saying the only way to know is to hook up a dc load meter when you’re cranking the engine. My manual doesn’t say anything electrical other than “Battery Rating: 465 marine cranking amps (MCA) or 350 vocals cranking amps (CCA)” and “Ampere hours (Ah): 70-100”

I imagine the 70-100ah has to do with the alternator, but does the battery rating mean the starter will trip a 200a breaker? Will it blow a 50a terminal fuse if I need to start the motor on the house battery?

Should I change my setup and have the fused positive terminals from Cranker and House connected to 1 & 2 on the perko respectively, but then have another cable 4awg directly from the cranker battery positive post to the starter motor, skipping the perko completely for that circuit?

If that’s the case, my mind starts to tell me the proper spot for a big terminal fuse may be, instead, on the perko “common” post, and attached to the short cable from that post to the fuse box, and the long 4awg down the bilge to the starter motor also connected directly to the common post, thus allowing each of the batteries to start the motor without a fuse on the line, and to also keep the ability to disconnect the system completely when I’m not around. But then again that terminal fuse would be greater than 7” away.

My head is starting to spin! Maybe I should just dump the motor and electronics and install some oarlocks and hand water pump lol

Edit: this video seems to answer a few of my questions

[Be Free]

Yes, you need a fuse between the house battery and the Perko switch. Not putting a fuse on the starter battery is acceptable.

There are two things to consider when sizing the fuse on the house bank:

• The maximum load you plan to put on the circuit

• The maximum load the wire can support in case of an overload / short circuit

Overeasy gave you good advice on the first case. You want your fuse to be around 25% larger than your expected loads so that you don't get nuisance trips.

The other thing you need to consider is how much current a 6awg cable can handle. Depending on the type of wire and insulation (I'm assuming that you don't have the wire bundled with others or running through a very hot area) your 6awg wire will carry between 95 and 120 Amps. The BMS in your lithium battery should shut down before it can melt your battery cable; the fuse is there to protect the wire in case it doesn't.

You have to do the math regarding current and future loads. Size your cables for the loads you reasonably expect to have when you are done and then size your fuses accordingly.

Ok great stuff. I upgraded every 6awg to 4awg, and I think I’m going to put a 50 fuse on for now.

I think that was a wise choice. #6 would not have given you much room to add stuff (as we all do) and you will get less voltage drop on the #4.

There is no problem with putting a smaller fuse on a larger wire as long as you don't plan to exceed the capacity of the fuse. I have 60 Amp fuses on my #4 house battery cables because that is around 125% of the current I should ever see (by design).

[louiseravot]

Sounds like you tackled a massive wiring mess and turned it into a clean, functional setup—nice job! The 5A fuse should work fine; it might just blow a bit sooner than a 6A. Great work getting everything organized and safe! If you ever need to verify regional electrical standards or postal codes for your projects, this postal code lookup site is a handy resource.

[OverEasy]

Hi TheLandLady!

I’d like a video of you rowing your Mac! That would be awesome!
Could you also get it while manually doing the hand bilge pump? That would be something to see!

What is the make, model and year of your engine?
With that information it can be determined that the fuse or circuit breaker that protects the cabling to the engine will be more than what your engine should ever require for cranking.

The old timey ‘not fusing’ the engine came from an era when clods cobbled crap together with crud sacavenged from gods knows where and didn’t have the sense to properly size the circuit components or ensure they carried the relevant fuse spares. (I’ve not only seen boats wired with old discarded undersized Romex but 70 year old cotton braid wire from old knob and tube era Victorian houses along with open knife switches and open frame screw in socket fuses if they had fuses at all.) In those “dark ages” folks were concerned that having a fuse blow while out on the water would leave them “stranded”…. So the short sighted approach is to not have fuses rather than having a properly implemented circuit. The argument for not having a fuse, especially given the readily availability of resettable circuit breakers is a poor one. Same with inadequately sized and type cables. These are readily available at/from a variety of sources to virtually anyone. The phrase ‘Penny wise - Pound foolish’ is as true today as it was in pre-colonial times.

In our setup we have a Suzuki DF60AV 2022 engine that we start through a 60Amp resettable circuit breaker and marine grade #4 AWG stranded wire (it can easily handle up to 75 amps) run through flex conduit, from either or both of our onboard batteries. The circuit breaker has never tripped.




Some folks get the recommended battery size for an engine confused with the actual current draw for the engine. They are not the same.
If one was to actually ever draw the 650 cranking amp capacity of a typical marine battery to start an engine then you’ve get something seriously wrong with your engine… (plus your gonna need several parallel 0 gauge wire runs!) Typically 50 amps is more than sufficient to start even a old 90 hp motor.

IMHO If someone needs more than 60 amps to turn over their engine then something is seriously amiss and needs looking into.

Similarly when looking at the alternator output…if your alternator is ever dumping back 70-100 amps you have a serious problem that you need to sort out like an internally shorted battery or cabling short…(neither to be ignored and why it’s nice to be able to select or isolate batteries).

Our wiring has the batteries and ‘Perko’ in close proximity to each other so we run the battery positives to the ‘Perko’ and the out put from the ‘Perko’ directly to the circuit breaker. From there the output from the circuit breaker routs to the main bus bar feeding the engine and the ‘house distribution bus’.






My electrical system is all push to reset circuit breakers for each application load.
While I was at it I pre-emptively added several spares for future (as yet unspecified) use.

All that said, if I were to have my batteries further away from the ‘Perko’ than I do then I’d be putting slow blow battery terminal high capacity fuses on each of my batteries and ensure I carry several spares along with any necessary tools in a readily accessible identifiable kit in close proximity to the batteries. This would keep the battery output cables protected. I’d also be placing those battery output cables in an additional protective sheathing if I were to run them under the floor, behind panels or through the bilges. I’d still keep the same circuit breaker on the ‘Perko’ output as having a circuit breaker trip that I can reset is my preference vs having to pull and replace fuses.

Best Regards,
Over Easy

[TheLandlady]

Sounds like you tackled a massive wiring mess and turned it into a clean, functional setup—nice job! The 5A fuse should be fine; it just might blow a little sooner than a 6A. Great work getting everything sorted and safe!

Thanks! So far no blow with everything on so it should be good to go

[Russ]

In our setup we have a Suzuki DF60AV 2022 engine that we start through a 60Amp resettable circuit breaker and marine grade #4 AWG stranded wire (it can easily handle up to 75 amps) run through flex conduit, from either or both of our onboard batteries. The circuit breaker has never tripped.

That's interesting. Proves the starter motor on our outboards are very low consumption. Less than 60 amps.

I have a jumper pack onboard for emergency starting. That same pack jumped my truck when it was -10 degrees outside. So I know it will easily start my outboard easily.

[TheLandlady]

Hi TheLandLady!

I’d like a video of you rowing your Mac! That would be awesome!
Could you also get it while manually doing the hand bilge pump? That would be something to see!

What is the make, model and year of your engine?
With that information it can be determined that the fuse or circuit breaker that protects the cabling to the engine will be more than what your engine should ever require for cranking.

The old timey ‘not fusing’ the engine came from an era when clods cobbled crap together with crud sacavenged from gods knows where and didn’t have the sense to properly size the circuit components or ensure they carried the relevant fuse spares. (I’ve not only seen boats wired with old discarded undersized Romex but 70 year old cotton braid wire from old knob and tube era Victorian houses along with open knife switches and open frame screw in socket fuses if they had fuses at all.) In those “dark ages” folks were concerned that having a fuse blow while out on the water would leave them “stranded”…. So the short sighted approach is to not have fuses rather than having a properly implemented circuit. The argument for not having a fuse, especially given the readily availability of resettable circuit breakers is a poor one. Same with inadequately sized and type cables. These are readily available at/from a variety of sources to virtually anyone. The phrase ‘Penny wise - Pound foolish’ is as true today as it was in pre-colonial times.

In our setup we have a Suzuki DF60AV 2022 engine that we start through a 60Amp resettable circuit breaker and marine grade #4 AWG stranded wire (it can easily handle up to 75 amps) run through flex conduit, from either or both of our onboard batteries. The circuit breaker has never tripped.




Some folks get the recommended battery size for an engine confused with the actual current draw for the engine. They are not the same.
If one was to actually ever draw the 650 cranking amp capacity of a typical marine battery to start an engine then you’ve get something seriously wrong with your engine… (plus your gonna need several parallel 0 gauge wire runs!) Typically 50 amps is more than sufficient to start even a old 90 hp motor.

IMHO If someone needs more than 60 amps to turn over their engine then something is seriously amiss and needs looking into.

Similarly when looking at the alternator output…if your alternator is ever dumping back 70-100 amps you have a serious problem that you need to sort out like an internally shorted battery or cabling short…(neither to be ignored and why it’s nice to be able to select or isolate batteries).

Our wiring has the batteries and ‘Perko’ in close proximity to each other so we run the battery positives to the ‘Perko’ and the out put from the ‘Perko’ directly to the circuit breaker. From there the output from the circuit breaker routs to the main bus bar feeding the engine and the ‘house distribution bus’.






My electrical system is all push to reset circuit breakers for each application load.
While I was at it I pre-emptively added several spares for future (as yet unspecified) use.

All that said, if I were to have my batteries further away from the ‘Perko’ than I do then I’d be putting slow blow battery terminal high capacity fuses on each of my batteries and ensure I carry several spares along with any necessary tools in a readily accessible identifiable kit in close proximity to the batteries. This would keep the battery output cables protected. I’d also be placing those battery output cables in an additional protective sheathing if I were to run them under the floor, behind panels or through the bilges. I’d still keep the same circuit breaker on the ‘Perko’ output as having a circuit breaker trip that I can reset is my preference vs having to pull and replace fuses.

Best Regards,
Over Easy

Ok I think I’d be happy and safe with a 100a slow blow on each positive battery terminal. Again thank you for the deep analysis OE, your setup looks great!

Edit: Oops forgot to say my motor is a 2 stroke 50hp Mercury ELPTO built April 2008. Pic is the sticker. Also, I realized I never posted the pics I took when we rafted up that night in mallets bay!

[TheLandlady]

Ok following up, I finally managed to get to the boat and not leave anything at home. All the cables are now 4awg, both positives are terminal fused with 100a slow blow fuses, I added some insulation boots they were lying around and they may not fit the best but they cover the fuses. Also I kept the AC battery charger lines connected directly to the battery, but they have their own fuses. Everything seems to be working just fine.

Also I brought the stereo system back to life by replacing its 15a inline fuse, pretty slick to have music coming thru the speakers in the cabin! The two in the cockpit don’t really work but I’ll have to dig a little deeper to see why. And finally I found on FB market, after a few months of searching all over the place, a NOS Standard horizon remote handheld to replace the one with the crumbled cord that came with Seaweed, and it works great! I’m still going to try and solder a new cord onto the old one but for now I have working radio at the helm.

Thanks for the help forum friends!

[OverEasy]

Hi TheLandLady!

Thanks for the photos!
That was a great evening for both of us!
I’m glad we were able to do that!
Thank you!

Glad you were able to get all that done!
Fantastic!
There should be rightly earned great sense of accomplishment and peace of mind with what you’ve done!
Kudos to you!

MacGregor says ‘Hi!’ to your wife and little girl too!


Best Regards,
Over Easy