Electrical Issues after replacing trim switch/sensor 7.4 EFI/MPI

[shsmith5595]

My trim up hasn't been working so I jumped the hurdle yesterday of replacing the trim switch on the motor. Trim sensor was working but I replaced it as well while I was in there. Everything worked good, trim and gauge were both functioning properly. Fired her up and went for a spin, came back and noticed a funky burning smell coming from the compartment. Tried to fire up the blower and it wouldn't come on. Turned the key back on and got a rapid beeping alarm. Still no blower. Turned back off and back on to no beep. Turned off the batteries at the perko and let it sit overnight to cool and went back down this morning. Blower still wouldn't work, first key to on turn had a faint beeping then nothing.

Checked the blower breaker at the dash and it was tripped. Reset it but still no blower. Gauges on the dash also appear to be inaccurate now--no battery voltage, gas gauge isn't where it should be, trim gauge partially works but isn't accurate. Motor won't crank at all. My guess is that a wire got moved into a hot spot and melted after I replaced the trim switch and sensor. Looked all through the motor and couldn't see anything obviously melted or out of place. Checked all the fuses by the 50A and they were good. Tried to press the 50A breaker on the motor but it wouldn't budge.

Any suggestions on what I might have messed up? I've got a voltmeter but I'm not sure where to start to begin tracing back to locate what the issue is. Motor is a Mercruiser Gen V 7.4LX Bravo 454 MPI/EFI on a 1996 Searay 28BR.

 

[shsmith5595]

My trim up hasn't been working so I jumped the hurdle yesterday of replacing the trim switch on the motor. Trim sensor was working but I replaced it as well while I was in there. Everything worked good, trim and gauge were both functioning properly. Fired her up and went for a spin, came back and noticed a funky burning smell coming from the compartment. Tried to fire up the blower and it wouldn't come on. Turned the key back on and got a rapid beeping alarm. Still no blower. Turned back off and back on to no beep. Turned off the batteries at the perko and let it sit overnight to cool and went back down this morning. Blower still wouldn't work, first key to on turn had a faint beeping then nothing.

Checked the blower breaker at the dash and it was tripped. Reset it but still no blower. Gauges on the dash also appear to be inaccurate now--no battery voltage, gas gauge isn't where it should be, trim gauge partially works but isn't accurate. Motor won't crank at all. My guess is that a wire got moved into a hot spot and melted after I replaced the trim switch and sensor. Looked all through the motor and couldn't see anything obviously melted or out of place. Checked all the fuses by the 50A and they were good. Tried to press the 50A breaker on the motor but it wouldn't budge.

Any suggestions on what I might have messed up? I've got a voltmeter but I'm not sure where to start to begin tracing back to locate what the issue is. Motor is a Mercruiser Gen V 7.4LX Bravo 454 MPI/EFI on a 1996 Searay 28BR.

After some more tracing it looks like the 90A fuse is melted to hell which I think explains the symptoms I’m having. Now just trying to trace the source. Guessing something got moved yesterday that is causing a short. Any suggestions on what would be likely around the trim sensor or switch wires that would be causing this? Seemingly whatever it is isn’t essential to running since I made it back to the dock fine, but I could have just gotten lucky. I’m doubtful it’s anything with the trim itself causing this but I could be wrong.

 

[alldodge]

To melt the 90 amp and not have it just blow, wonder if someone prior replaced the fuse with a washer.

Just keep looking and its most likely back by the starter

 

[nola mike]

Which 90a? Alternator or trim pump?

 

[shsmith5595]

Which 90a? Alternator or trim pump?

Alternator

 

[shsmith5595]

Still no luck finding the source. Added some pictures of the fuse. I peeled back the wire loom on the alternator wires and they aren’t crispy which surprised me. The loom is melted in a few spots on the outside I’m guessing from the engine.

 

[alldodge]

It looks like both the ALT feed and motor feed are melted? If that's the case then it shouldn't happen unless the battery cable was installed to bypass the fuse

 

[shsmith5595]

When I took it off it had the big battery cable coming off the perko going onto the starter motor and the fuse, and then the other side of the fuse had the orange ALT wire and the smaller red wire coming off. Yellow/red going to slave was attached to smaller bolt on the starter. I think that’s how it’s supposed to be? At this point I’m thinking I will check and clean my grounds and then reloom the alternator run and make sure it’s clear of the engine and then cross my fingers that it’s fixed.

 

[nola mike]

Yeah that's correct. What did the wire on the other side of the fuse look like? It looks like your current came from the alt going backwards.

 

[shsmith5595]

Yeah that's correct. What did the wire on the other side of the fuse look like? It looks like your current came from the alt going backwards.

It was in good shape

 

[alldodge]

Its wired correctly but there must not have been a fuse inside the fuse holder

 

[nola mike]

Its wired correctly but there must not have been a fuse inside the fuse holder
View attachment 365492

IDK, I would have expected the starter side to be melted as well. Wondering if full fat battery power from the trim circuit found its way back to the alt. Although it still should have made it back to the 50a breaker as well I think.

 

[shsmith5595]

IDK, I would have expected the starter side to be melted as well. Wondering if full fat battery power from the trim circuit found its way back to the alt. Although it still should have made it back to the 50a breaker as well I think.

Yeah since it started after I replaced the trim sensor and switch I've wondered if the issues are somehow connected other than coincidentally moving something else around that made contact or loosened a wire. My trim is wired independently of the perko direct to the battery, though, so I would have thought if I was getting some kind of flow from the trim circuit I would have continued to see things frying after I killed the main power.

 

[alldodge]

My trim is wired independently of the perko direct to the battery

You sure, most have a lead from the starter post to the trim

 

[shsmith5595]

I’ll double check this evening but I’m pretty certain it’s wired separate and I can trim with the perko off.

 

[shsmith5595]

Yes, pretty sure it’s wired independently. Was able to trim still with perko off and disconnected from motor. Appears to have its own red and black to the battery.

 

[shsmith5595]

Went ahead and replaced the fuse. Checked all the wiring I could and added more loom in some spots that looked iffy. Gauges are all back to working and the motor turned over and idled but the blower still is kaput. I reset the blower breaker and the light on the switch was good, but then it tripped again after being on for a few seconds while I tried to check the voltage at the blower. Going to have to bring a helper down to check if maybe the blower is out. The key chirp was about a continuous 3 second beep whereas usually it’s 2 beeps back to back, so I’m thinking I’m not quite out of the woods yet. Was dark when I got everything situated so I didn’t get a chance to take it out of the dock (also still a little hesitant to trust it at this point).

 

[alldodge]

Seeing the automotive battery terminals was wonder what the brand of boat you have?

A 3 second beep isn't good. Have a motor serial number?

 

[shsmith5595]

It’s a SeaRay 280BR. The motor serial is 0F602631

 

[alldodge]

Thanks, MEFI 1 with VST
The MEFI 1 is not very smart, but could be a voltage issue. Check with it running to see if your getting 14.5V from the ALT with motor above 1500 or so rpm.

Can scan for codes using a 12V resistor LED or multimeter with a tone function. Insert paper clip, turn key ON and count flashes or tones