Engine Produced Hot Smell

[joc1212]

Q1: what causes my 2016 Mercury 150-HP FOURSTROKE engine to emit an order of "hot" after a six-mile run at an engine speed of never more than 3,200-RPM during which there was good water flow from the overboard confidence stream nozzle, good water pressure indicated on an electronic Smartcraft cooling water pressure gauges, and good oil pressure.?

The odor smelled like hot wiring. Note: the engine alternator was just replaced before this run because the original engine alternator failed after 245-hours of engine run time, and the cause has never been determined.

The engine is charging two batteries: one GROUP 27 flooded cell lead-acid deep-cycle battery, and one GROUP 24 sealed absorbed glass mat cranking battery.

The voltmeter function on the SmartCraft gauges shows battery voltage is 14.5-Volts.

I have no idea why the original alternator failed. I did not take off the engine cowling due to time constraints. While flushing the engine I smelled the "hot wiring" odor

Could having an AGM and a flooded cell be part of any of the electrical malfunction?

These two batteries were in the boat when I bought it.

[jimh]

Q2: Is the engine perpetually trying to charge two large Ampere-hour storage capacity 12-Volt lead-acid batteries wired in parallel?

The load of two batteries with very large capacity to store electrical energy that are wired in parallel can be too much for the alternator on an outboard engine as a continual operating load.

Is the alternator on your engine a separate assembly, driven by a belt and pulley arrangement from the engine crankshaft?

Q3: are there any other loads on the engine electrical output that could be consuming a lot of electrical power?

[jimh]

Q1: what causes my 2016 Mercury 150-HP FOURSTROKE engine to emit an order of "hot"...?

Generally the odor of hot electrical components is caused by those components becoming too warm. In electrical circuits, the more current flowing in the circuit, the more voltage drop that occurs. The voltage drop in Volts multiplied by the current flow in Amperes produces a dissipation of electrical energy in Watts in the form of heat. Well designed electrical circuits anticipate some heating due to voltage drop across their internal resistances, but when current flow is very large, more heat will be produced than anticipated, leading to more heating of the electrical components.

The electrical characteristic of the odor is probably from wire insulation getting too warm.

The human nose can be a good investigative tool. The next time the odor of hot electrical components is detected, remove the engine cowling and sniff around for the source. Be careful: don't burn your nose.

Also, a non-contact infrared thermometer can be an excellent tool to locate hot electrical components. Such a thermometer will have many additional uses, and buying one for about $50 or less will be a good investment in a very useful tool to supplement your nose or your finger in finding excessive heat sources.

[jimh]

Q4: surely with all the instrumentation available from Smartcraft, you must have an engine temperature gauge; what was the engine temperature when you smelled the odor of hot electrical components?

[Phil T]

ASIDE:I note from a prior post you have a newly acquired 2016 Outrage 190.
[Moderator note: the OP may have mentioned a specific boat, and I probably deleted that information, as the engine and battery interaction really do not depend on the boat brand.]

(Note from author to Moderator: The battery information "probably deleted" is actually relevant as you can see below as there appears to be a modification from the factory supplied battery management system. Given your probable deletion, I had to ask questions that may have possibly been answered in the undeleted post. You should not be deleting what members post regardless. Otherwise what the hell are we doing here?)

Have you reviewed the owners manual for battery management?

See section 4:
https://www.bostonwhaler.com/content/dam/boston-whaler/technical/resources/190-Outrage-Owners-Manual-2016.pdf

The standard feature is a single starting battery (AGM Group 27) with an OFF-ON battery switch.

Q5: why was a second battery added?

Q6: what is wired to the second battery?

Q7: isn't it proper to charge one battery at a time?

Q8: is it not the recommendation to have the battery selector to both only for "emergency" starting?

To me you may be damaging your electrical system running with the selector in "both."

Jim is the electrical engineer and can validate theses statements.

[jimh]

As PHIL T mentions, operating the boat with two batteries and connected them in parallel by using a typical OFF-1-BOTH-2 battery switch set to the BOTH position all the time is not the proper method to manage battery use.

If a previous owner modified the primary battery power distribution wiring to add an OFF-1-BOTH-2 battery switch and adding a second battery, thus replacing the OEM configuration with a single battery and an OFF-ON battery switch, there is no guarantee the wiring was done properly. Maybe the "hot electrical smell" is due to the wire size that was used being too small to handle the current.

There are many outstanding questions to the OP, so I will await his reply.