Fusible Link keeps blowing!

[Jutty]

Hi all,

First time here. I have a 2012 Manitou Oasis VP pontoon with a Merc Optimax Pro XS two-stroke 150. My fusible link keeps blowing. The 100 amp inline off the alternator. I replaced it with an inline 100 amp waterproof circuit breaker because the original fuse is sealed and they are 70.00 a piece for a new one. I haven't messed with any other wiring anywhere. It will pop for no reason and then might work fine for 5-6 hours without popping. It has done this since almost new in 2012. The motor runs fine and all electrical systems (very simple stuff, no major amp draws) work as they should. The boat has a factory installed two battery (a, b, a+b, off) system. I realize the fusible link should pop when there is a reverse polarity situation but the thing is, it doesn't pop all the time, but pretty much once or twice on a day outing. It's pretty strange to me.
Anyone have any guesses as to why this is happening in such a manner? Thanks ahead of time!

[Savage]

The fusible link blows when the polarity is crossed at the battery, like when wiring connections and battery chargers are connected with crossed polarity.

[Jutty]

Yes, I had researched and read that it blows when a reverse polarity occurs as I mentioned in my post. But it happens to my motor randomly and not all the time. I would assume if something was wired backwards it would continously/immediately blow. It doesn't do that. Which is why I can't figure it out. I'm not a mechanic, but my situation occurs when there are no chargers or anything connected. It happens on the water while running. But not all the time. How could the polarity reverse when it's not being touched?

[g352nv]

Wire grounding out? Alternator going bad?

[Savage]

Connect the motor to one battery and eliminate the battery switch for testing purposes.

[billnorman1]

Probably a short. See if it is associated with turning the steering wheel. Since the boat is metal, any where that wire contacts the hull will short it if it is bare. (insulation damaged)

[EuropeanAM]

Please take a moment to Review the Announcements at the top of the Forum, and be sure to provide the REQUIRED info when posting. Thanks!

Technically the fusible link protects the alternator and other expensive electrical components from being damaged due to OVERCURRENT. This can be due to reverse polarity OR due to a dead-short in the high-amperage cables.

Given the situation, pull the entire battery cable set and inspect every inch for damage. Isolate the engine to ONE battery, directly connected.

Also inspect the Fusible Link Harness for chafing or shorting to ground. Strongly recommend going back to the OEM Fusible Link Harness.

Moving thread to the 2.5L Forum for you.

[Jutty]

Thanks guys!

[Jasay]

Jutty, did you ever get this figured out. I'm thinking about doing the circuit breaker instead of fusible link.

[lpugh]

Seen the cables shorted in the rigging tube several times..

[SilverFox579]

Jutty, did you ever get this figured out. I'm thinking about doing the circuit breaker instead of fusible link.

Jutty has not logged in here since Aug 2020...

[styler]

For me I always like to read these forums and see the recommended advice giving. Its a plus when we see the advise taken and the issue resolved. I wish guys would post the results instead of asking a few questions and disappearing.

[JOE54]

^^^ +1