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Battery Fuse Help

rudyengrudyeng Posts: 546 Officer
My boat blew this Eaton 50A battery fuse and did not charge the battery. Had to call sea tow $ 900.  I want to upgrade the fuse system to make it idiot proof.  I could not tell the fuse was blown but got a low battery indication then an hour later both motors died.  I was 40 miles away from land. This is what i found when i got home. The top fuse was the 5 A motor clean power and bottom was the battery fuse. Not sure if that came form the isolator or switch. I blew 4 of the 50 amps trying to get the motors started and messing with the settings. I think they are undersized because the 300 V8 Verados provide much more than 50 A

Any help would be greatly appreciated




  • MelbourneMarkMelbourneMark Posts: 3,843 Captain
    Man, thats a lot of amps to blow.   I would look up your motor manual and see what it recommends. 
  • larrywittlarrywitt Posts: 2,924 Moderator
    Is this on your brand new ride, if it is some thing not right with the rigging. 
  • The Cat's EyeThe Cat's Eye Posts: 1,741 Captain
    edited May 2021 #4

    It seems you have been running that boat for a while now without blowing any fuses so I don’t think the problem has anything to do with the size of the fuses. Something else is amiss. Have you recently installed any major electronics?  Try disconnecting some of your electronic devices and see if the fuses don’t blow.  Another thing to consider is if you have installed several electronic components that all draw say 15-20 amps onto one single circuit to the battery that could explain why you are blowing the 50 amp fuse. If that is the case you need to add another circuit directly to the battery to divide the load. The smaller 15-20 amp fuses for electronic components will probably not blow since the current being drawn by a single component might not be the problem.

     I think it might be time for you to take it to a professional to check out the output from the rectifiers and voltage regulators if the problem is NOT too many electronic components on the one 50 amp circuit.

    I would also have a second battery installed and get a contract with Boat US Towing After you determine the problem.

  • rudyengrudyeng Posts: 546 Officer
    edited May 2021 #5
    I found the Merc wiring diagram and it actually shows the alternator on the new 300 V-8 Verado at WOT puts out 115 Amps but the net amps is a little less. I'm guessing 80 amps max. That's why it's blowing a 50 amp fuse. I looked up the part number  for my motors with my local Merc service guy and he cross referenced a Merc 90 Amp fuse. That makes more sense.  It's crazy that the builder used a 80 amp fuse for the stereo and a 50 amp fuse of the boats alternator.

    The Merc wiring diagram calls for a 150 amp fuse but thats crazy.

  • conchydongconchydong Posts: 15,488 AG
    That sucks. I hate to say it but I’m becoming less and less impressed with your builder. Lotta folks can turn out a nice piece of fiberglass with the mold but the other half is rigging up properly.

    “Everyone behaves badly--given the chance.”
    ― Ernest Hemingway

  • rudyengrudyeng Posts: 546 Officer
    Found the Merc Alternator output for my motor. The 300 V-8 Verado puts out 115 Amps but the battery will probably see about 80 Amps at WOT.  That explains how i blew the 50 Amp fuses.  This was the first trip that i opened it up all the way WOT.  Hence the overload and blown fuses.

    I purchased a clamp on amp meter online. I will follow up with actual numbers at idle,cruise & WOT

  • Tony RomaTony Roma Posts: 4,710 Captain
    A brand spanking new build leaves you stranded 40 miles offshore? You are a patient man. 
  • 4WARD4WARD Posts: 3,185 Captain
    Tony Roma said:
    A brand spanking new build leaves you stranded 40 miles offshore? You are a patient man. 
    That was polite 😉.
    Rudy, If you don’t blow a lot more than a fuse soon. I am going to have to stop reading your posts.
    "I hate graveyards and old pawn shops
    For they always bring me tears
    I can't forgive the way they rob me
    Of my childhood souvenirs"... John Prine
  • rudyengrudyeng Posts: 546 Officer
    The original Verado alternator put out 70 amps. The New V-8 300's puts out 115 Amps.  Someone did not catch that during the rigging. The wire size is rated for 150 Amps so it's just a fuse issue.

    Yeah not happy about blowing my family vacation and being stranded 40 miles away.  I asked the boat manufacturer to reimburse me for the towing expenses. That's the very least they can do.

  • rock_fishrock_fish Posts: 12,224 AG
    edited May 2021 #11
    no tow insurance?

    Proud supporter of the anti fishing, terroristic (lol what?) movement known as Greenpeace.
  • cortrcortr Posts: 538 Officer
    You might need to have a professional inspection by certified marine surveyor. You need to be confident that there are not other issues there are not easily detected. 
    Agree with 4Ward. You have been too nice to the builder
  • rudyengrudyeng Posts: 546 Officer
    I could not believe how many Amps the new V-8 Verado puts out. This pic is at idle 29.9 Amps. As i extrapolated the amp readings at 1200 rpm's it is very clear that the motors are easily putting out over 100 amps at (WOT) Boat is on a trailer so i did not want to rev it to get a reading.

    Yes i do have tow insurance but do not wish to place a claim. It's very hard to bind a high value boat in Miami Dade County.  When you do get a policy the cost is sky high. I don't want to risk losing coverage or an increase in cost. I'm asking the builder to pay for the tow and we are currently negotiating

  • polliwogpolliwog Posts: 355 Deckhand
    Boat insurance isn't the same as Tow insurance.  That tow insurance is bgt to solve being stuck and needing a tow in. I would always call the problem in and expect it to be taken care of.
  • CapnSkipCapnSkip Posts: 58 Deckhand
    Most boat insurance policies only cover up to about $500 for towing which doesn't amount to much depending on how far you need to be towed. You may want to look into Boat US or Sea Tow for towing. $150 a year is well worth it.
  • FletchFletch Posts: 2,580 Moderator
    I've used something similar to this in past with good results. Auto-resetting thermal breaker...
    "Ninety percent I'll spend on good times, women and Irish whiskey. The other ten percent, I'll probably waste..."
    -- Tug McGraw on getting a raise

    Get Down Fishing Charters - Port Canaveral, Florida
  • gogittumgogittum Posts: 4,237 Captain
    edited May 2021 #17
    Fletch said:
    I've used something similar to this in past with good results. Auto-resetting thermal breaker...
    I used a similar self-resetting breaker on the boat trailer winch connection at the battery in my van.  It worked well for momentary surges.  Not sure how it'd be for a direct short.
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