Ignition? Wires heating up during engine operation

[Matts5150]

Merc will mail that to you just call and ask 920-929-5040

Great to know thanks I'll give them a shout

 

[Thornton69]

Thanks mine is different it's newer I think than the older ones I found a similar wiring diagram and it doesn't match mine mine definitely has a bank of four fuses and when you look up the parts using my engine serial number it shows you 20 amp fuses so I'm correct on the fuses I just wish I could find the actual wiring diagram for my engine I'm sure if something's are similar but I really need the exact one to trace out these wires and see if there's a broken connection somewhere on the runs and clean each terminal they terminate at

Keep in mind, although resistance from bad connections will make heat and even melt things in the close vicinity, they will reduce current which will not blow the fuses or trip breakers. If you are having problems with fuses or breakers popping, you need to look for shorts. A short does not have to be directly to ground. It can simply just be a shorter path to ground in the failed windings of a relay or fuel pump for example. That's where your Ohm meter is handy if you know the correct spec of the component. You can also use Ohm's law for a general reference. The voltage is equal to the current multiplied by the resistance or I=V/R.

 

[km1125]

Thanks mine is different it's newer I think than the older ones I found a similar wiring diagram and it doesn't match mine mine definitely has a bank of four fuses and when you look up the parts using my engine serial number it shows you 20 amp fuses so I'm correct on the fuses I just wish I could find the actual wiring diagram for my engine I'm sure if something's are similar but I really need the exact one to trace out these wires and see if there's a broken connection somewhere on the runs and clean each terminal they terminate at

Early in the thread you wrote "Keep in mind those pink wires are thin possibly 18 gauge." Is it possible they're much larger? 18 GA would be too small for 20A circuits, especially if there's a bundle of wires (meaning more than ONE).

 

[Matts5150]

Early in the thread you wrote "Keep in mind those pink wires are thin possibly 18 gauge." Is it possible they're much larger? 18 GA would be too small for 20A circuits, especially if there's a bundle of wires (meaning more than ONE).

That's a good point they are definitely roughly around 18 gauge and when looking at the manuals it was showing 20 amp fuses. I still have not figured out the problem yet I went a whole season melting several fuses. I really want to get down and replace that 90 AMP fuse on the starter and clean those connections but man there is no room to get down there without taking off the manifold and riser which I don't really want to do because that means draining 5 gallons of antifreeze because I have a closed circuit system and it's still going to be a pain because there's no room to work on the starboard side of the engine even with manifold off. I might just have to bite the bullet and pay someone to get down in there. If there is continuous power by that 90 AMP fuse it is a good possibility that is where my problem lies. I would like to just turn the ignition on without starting the engine and leave it for several minutes that way and see if the wire heats up without engine running but I believe it has to be running for this to happen but I need to confirm

 

[ttmott]

It looks as there is a bad wire termination on that fuse holder. Common cause of high heat.
Replace the fuse holder and get your fuses and circuit breakers back in order.
Now, after getting the deficiencies corrected and you are blowing fuses or tripping circuit breakers then that is something else.

 

[scoflaw]

No need to drain anything, pull the hose off the bottom of the manifold and plug it then remove it

 

[Matts5150]

It looks as there is a bad wire termination on that fuse holder. Common cause of high heat.
Replace the fuse holder and get your fuses and circuit breakers back in order.
Now, after getting the deficiencies corrected and you are blowing fuses or tripping circuit breakers then that is something else.

That's a brand new blade fuse Marine grade holder that I installed and it's still melted the factory one was a mini blade fuse that came with a bank of four. So I don't believe it's the fuse holder the wires heat up as well got to be something else somewhere.

 

[Matts5150]

I thought of something else that could potentially be my problem but I doubt the factory would have misspined the wires. So the original fuse block the two wires came out of that melted where from a bank of four fuses I'm wondering if the wires out of the bank of four we're not matched up properly. I would need to find someone with the exact year motor and boat if they could take a picture of their fuse holder I could see the wires and see if mine matches up exactly.

Anyone have a 2007 or also have a bank of 4 mini fuse terminal on top of the engine that's near the port side manifold close to the riser? If anyone has the same configuration would be very helpful if they can snap a picture of the bottom of that bank of four fuse terminal. I forget what all fuses are for but I believe at least one of them is for the fuel pump they should be all 20 amp mini blade fuses in there.

 

[Matts5150]

Here is a picture of the blade fuse holder that I installed a year ago. I will also attach a picture of the original OEM Bank of four fuse holder that's still in use you'll see that it's melted as well

 

[scoflaw]

I would think you need to drain because once you pull manifold off the coolant that's sitting in the block will pour out and may risk coolant draining into the oil passages definitely not a good idea. Especially when you loosen the manifold when it starts to separate from the block the coolant that's in the passageways is going to start to find its way fast and right next to the coolant passageway is the exhaust passage

There is no coolant behind the exhaust manifold. It travels from the bottom of the manifold up and out from the riser back to the engine.

 

[Matts5150]

Bank of 4 mini fuse I removed two of the 4 because I noticed one of the other fuses we're getting warm as well so I installed two new fuse holders for those two that are separate now I'm just wondering if the original factory the wires were crossed.

 

[Matts5150]

There is no coolant behind the exhaust manifold. It travels from the bottom of the manifold up and out from the riser back to the engine.

Oh yes you are correct I totally forgot about that not sure what I was thinking and that's good to know I don't have to drain the system. Thanks for the reminder

 

[ttmott]

That's a brand new blade fuse Marine grade holder that I installed and it's still melted the factory one was a mini blade fuse that came with a bank of four. So I don't believe it's the fuse holder the wires heat up as well got to be something else somewhere.

Still, the fuse should let go before anything heated up. Fuses protect the wiring not the devices. So, either the wrong size fuse for the wire and connector or you still have a wire termination issue causing high current resistance.

 

[Matts5150]

Still, the fuse should let go before anything heated up. Fuses protect the wiring not the devices. So, either the wrong size fuse for the wire and connector or you still have a wire termination issue causing high current resistance.

The fuse does sometimes let go but the wires are always getting warm. Are you saying to put a lesser fuse in there instead of a 20 like a 10 or 15 I don't think that would stop it from heating up if anything the fuse would just pop quicker I could try that. When I get home today I'm going to turn the ignition on and leave it for a few minutes without starting I want to see if the wires heat up without engine running just with the ignition on hopefully that doesn't damage anything by doing that

 

[ttmott]

The fuse does sometimes let go but the wires are always getting warm. Are you saying to put a lesser fuse in there instead of a 20 like a 10 or 15 I don't think that would stop it from heating up if anything the fuse would just pop quicker I could try that. When I get home today I'm going to turn the ignition on and leave it for a few minutes without starting I want to see if the wires heat up without engine running just with the ignition on hopefully that doesn't damage anything by doing that

Yea, but rather a "lesser fuse" the correct fuse for the wiring. What should the correct one be?
Now, if you have the correctly rated fuse and the system blows the fuse then there are other things going on that need attention.

 

[Matts5150]

So I went down and I tested turning the ignition on all the way without starting the wires stayed cool it was until I started it up they started to warm up this time they didn't get so hot but they were warm I also noticed the same red with purple stripe wire goes to several locations I'm not sure if the red with purple stripe is a main wire like a power feed to several points. I also noticed by the 50 amp breaker the red with purple stripe wire leads to that as well and the wires connected to the 50 amp breaker on top of the engine was getting warm also while engine running I replaced that 50 amp breaker couple of years ago to rule that out so I doubt it's the breaker I'm wondering if that same red with purple stripe wire goes down to the starter. I also noticed the same red wire with purple stripe also leads to one of the three relays that sit on top of the engine those are not getting warm. I guess I really need to take that starboard manifold off and get down to the starter and replace that 90 amp fuse and while I'm down there cut all the wires and put new wire rings on them and while I'm at it I should just replace the starter assembly since it's original from 2007 and that it's a pain to get down in there might as well just rule all that out. Extremely tight in my bilge especially starboard side there's no room to get in there I have to lay on top of the engine and lean upside down that's not going to be fun LOL

 

[km1125]

Bottom line is that if those are really 18GA wires and you have a 20A fuse "protecting" the circuit something is WRONG. If you're believing that the documents show it should be a 20A fuse, then do you have any info on the documents that show what the wire size(s) should be?? They would NOT be 18GA for a 20A circuit.

 

[km1125]

Having access to a clamp-on DC ammeter would surely help isolate this issue.

 

[Matts5150]

If I were to purchase one of these what would I need to do to isolate the problem with one of them?

 

[Bill Curtis]

If I were to purchase one of these what would I need to do to isolate the problem with one of them?

Find out which circuits are indeed drawing too much current / or over fused considering actual circuit load.

A digital multi meter (some good clamp on ammeters functions as a DVM, also) will detect a bad connection / bad wire when used to measure voltage drop.

PS: for a 10 amp circuit, you need a 16 gauge wire. For a 20, a 12 gauge wire.
a 20 amp fuse on an 18 gauge wire is an invitation for at the least some melted wire /melted connectors (as you see in the pics), or for a fire.

Either learn proper marine wiring techniques, or leave it to a professional.