Blowing Ignition Fuse When Rev'd

[jsmaeb1215]

Hey all, our first day of our 2nd season of boating didn't go so well.

At the end of the year last year the boat was having some idling issues. Figured it was the carb, so I ended up picking up a reman from fly fishing carbs and swapped them out. Boat is now running much better and idles just like it should.

We took it out for our first day today and the boat was running great. Cruised for a bit at 25 mph and all seemed well. Put the throttle to the floor and it started to build up them boom boat dies and the 10amp ignition fuse is blown. Put in another turn the ignition and instantly blows. We ended up having to get towed in which is a bummer.

Get it backed into the garage, throw another fuse in, turn the ignition, and it doesn't blow. So I hook the boat up to the muffs to start her up and she fires up no issues. Let her run for 5 minutes or so and all seemed well. Gave her a rev and it blew another fuse as right around 3k rpms. I am stumped at this point and looking for any suggestions or experience. Never had a issue like this before the carb and I my gut tells me its a completely different issue, but at this point I am unsure.

I appreciate the input.

 

[GA_Boater]

And your motor and serial number is............................

 

[jsmaeb1215]

And your motor and serial number is............................

Ooops, was a long day.

96 Stingray 556zp is the boat
3.0 Merc
0F753377

Also want to make sure I am ok revving the boat up to 3k or so while on muffs for testing?

Found that the purple wire going to the alternator had a very very tiny bit of wire exposed which could have been shorting something out. I am unsure on this as the amount of wire showing is very small, but figured it was worth mentioning.

 

[Fun Times]

Try with the engine off, key on, put the throttle to wide open and see if it still blows the fuse. The cable may be rubbing on a power wire someplace or the power wire behind the throttle control handle may be frayed blowing the fuse.

What color wire is going to the fuse that's blowing out?

 

[jsmaeb1215]

Try with the engine off, key on, put the throttle to wide open and see if it still blows the fuse. The cable may be rubbing on a power wire someplace or the power wire behind the throttle control handle may be frayed blowing the fuse.

What color wire is going to the fuse that's blowing out?

The wire coming from the #1 fuse is red with a blue stripe. It says Ign 10A.

I repaired the purple wire going to the alternator. I am unable to reproduce the issue with the boat off. Although I am now unable to reproduce the issue when the boat is on. Need to find someone with a boat that could come out on the water with me just incase. Flagging people down is a bummer.

 

[Bt Doctur]

purple is the ign feed and nothing should be added to the ign circuit such as radios, amps, etc. Purple wire powers the ign module, the pressure senders, the choke,and the alt. Try unhooking the alt leads and retest.

 

[jsmaeb1215]

purple is the ign feed and nothing should be added to the ign circuit such as radios, amps, etc. Purple wire powers the ign module, the pressure senders, the choke,and the alt. Try unhooking the alt leads and retest.

Interesting, so by the sounds of it, the small bit of the purple wire could have been my issue.

The boat does have a radio and a fish finder. Both of which are wired to the fuse box but use their own fuse, is this considered separate from the ign circuit?

 

[Bt Doctur]

And the power feed for this fuse box comes from..........................................................

 

[jsmaeb1215]

And the power feed for this fuse box comes from.............................................. ............

I would imagine the battery, I am new to electrical issues so I am a bit ignorant on the subject. I have been digging and reading though, learning bits and pieces.

Not quite sure what you are getting at.

 

[Bt Doctur]

if you pulled the power from the ign side ,that would be adding a load to the ign circuit and blowing the fuse, if it has its own wire running back to the battery for ok.

 

[jsmaeb1215]

if you pulled the power from the ign side ,that would be adding a load to the ign circuit and blowing the fuse, if it has its own wire running back to the battery for ok.

We put close to 50 hours on the boat last season with this same configuration. I would think if its what your describing I would have come across it long ago.

Like I said the only thing which changed was a new carb which also came with a new choke.

I tried again today to reproduce the issue and I am unable to. As much as I don't believe it, the small issue with the purple wire might have been my root cause.

I want to take it back on he water soon to see if I can reproduce. I am open to any suggestions or ideas that might assist if the issue happens again out on the water. Disconnect the alternator, choke, anything riding on circuit?

I also tested my batteries are at 12.4v when shut off, and 14.4 when the boat is running, so my alternator seems to be doing its job.

 

[bspeth]

no do not rev it to 3k on muffs. The most I go is 15oo and only for s short time