Fuse blows when engine starts

[apallo1]

I have an 08 Tahoe with a 4.3L mercruiser engine. Boat started on its own last year in my driveway but didn't run long. my neighbor saw it and turned key on and off, it still ran. Disconnected negative battery lead and it still ran. Disconnected positive terminal and it finally died. Very strange. We decided to mess with it next year. So 2 weeks ago we dove into it. Had dreaded starter click. Pulled starter and had it rebuilt. With starter back in, I went to start it and after 2 tries it kicked over and died. At this point I lost all power to ignition switch. Still had power and good fuses at panel under the dash. traced main ingnition wire back behind carburetor and found 15amp mini fuse (also discussed in this thread) https://forums.iboats.com/forum/eng...hidden-fuse-on-4-3-tahoe-q4-please-help/page5
I replaced the fuse and the boat again would go to start but the minute the engine catches and is kicking over, fuse blows and it dies. I even replaced the ignition switch for grins. Im guessing I have a short somewhere but I don't know where. Ive checked all the wires against the motor and none are melted. Ive checked and cleaned battery leads and terminals. just hoping someone has had this issue before and can help out. Ive got a 5yr little girl who tells me every time she see's me, daddy I want boat!

 

[Bondo]

Boat started on its own last year in my driveway but didn't run long. my neighbor saw it and turned key on and off, it still ran.

Ayuh,..... Welcome Aboard,..... What happened with the boat, the very last time,.... Before this happened,..??

 

[apallo1]

I wish I had a good story but nothing really. Took it out July of last year, business as usual, parked it in driveway. 2-3 months later it starts on its own one day.

 

[bman440440]

could you possibly have rats/mice chewing things in your boat?

 

[TimTJR]

I just blew the same 15 amp fuse yesterday in my 4.3. I also found another blown 20 amp fuse in the wiring that is on top of the carburetor. It took me awhile to find these fuses. All I did was turned the key to the on position without starting it up to make sure I got power back to my dash. After reading this I am going to start the engine tomorrow and see if it blows the fuses again.

 

[GA_Boater]

When you fix the fuse problem or even before, replace the missing impeller and other damaged water pump parts. Dry running eats impellers.

 

[apallo1]

could you possibly have rats/mice chewing things in your boat?

It’s always possible but I’ve seen no damaged wires or rat droppings.

 

[apallo1]

When you fix the fuse problem or even before, replace the missing impeller and other damaged water pump parts. Dry running eats impellers.

Good to know, thank you.

 

[TimTJR]

I started my engine today after changing the fuses and it ran good. I just can't figure out why they blew in the first place.

 

[apallo1]

I started my engine today after changing the fuses and it ran good. I just can't figure out why they blew in the first place.

I’ve blown 6 fuses so far trying different solutions. Obviously none of them worked. Good to know at least one of us has a working boat.

 

[scoflaw]

As a last ditch effort, I will wrap the fuse in tin foil, run the motor for a minute or so then start feeling around for what is getting hot.

 

[apallo1]

I put a 20amp fuse in today. Blew that too. So I disconnected everything from the battery except the 2 large main cables, added 15amp fuse. Blew it. So far I’m up to 8 fuses.... and that doesn’t count the 2 I dropped cause I didn’t wanna set my beer down.....

 

[TurtleTamer]

Try disconnecting the alternator. Bad voltage regulator might do it.

 

[apallo1]

Yesterday I disconnected the 2 purple wires from the ignition switch and tried them individually. First time I lost the audible chime when key is turned, still blew the fuse when it started. Disconnected that wire and connected the other, fuse didn’t burn up, boat starts then dies. My guess is whatever this wire is connected to is responsible for keeping the engine going. Does anyone know? Im thinking there is either a break in the wire and it’s grounding out or whatever it’s feeding power to at the other end of the wire is bad.

 

[Bondo]

Well, for starters,.... What's the serial number of the motor,..??

All we know is it's a 4.3l from '08,.....

Did ya try TT's tip, disconnect the alternator,..??

If that fails,... Does the carb have an electric choke,..?? unplug it, 'n try again,.....
Electric fuel pump,..?? Test it,.....
Disconnect gray wires from the coil, 'n try,....

Yer chasin' a electrical gremlin, yer gonna go through some fuses,....
There's always the shake, wiggle, 'n tug test too,.....

 

[apallo1]

Well, for starters,.... What's the serial number of the motor,..??

All we know is it's a 4.3l from '08,.....

1A057519
Yes, I forgot to post I disconnected alternator, didn’t help. Same with carb and fuel pump. Checked continuity on coil as well the wires from ignition up to this fuse. All shows good.

 

[apallo1]

I just tied into fuse wire and ran a temporary wire to ignition, this also bypasses the run/stop switch on throttle, and the fuse didn’t blow, but the engine tries to start but won’t turn over. Does something in the 10pin connector also rely on power from this when I bypassed it?

 

[apallo1]

Ok, here’s something straight out of the twilight zone. So I run a temporary wire from fuse to ignition like yesterday. I also unplugged the fuel pump and shoved the leads from my tester into it to make sure I was getting 12v. I turned the key to start position and I don’t know why but I held it and the damn boat stayed running?!?!?! No active fuel source and holding the key in start and it ran for 5 sec until I let go and it died. Is it possible the 2 minor wires on the starter are backwards???? And how the hell is it running without gas?!?!?

 

[AShipShow]

Probably just enough gas in the bowl to run for a few seconds..

 

[apallo1]

Flipped wires on starter, starter spun backwards... so that wasn’t the problem. Boat will still run if I hold key in start position and run jumper wire from fuse to ignition bypassing 10pin connector and kill switch on throttle. I’m at my wits end....