Alternator smoking

[Fishstalker001]

2014 mercury four stroke sn 2B077716.

Had the boat boat out fishing and engine would not turn over (dead battery) put boat on
trailer and connected on board charger. Charger indicated an error as battery not detected.
Moved charger leads over from other bank and error followed. Installed new battery and
here is where the issue began. Walked away from the boat for a few and when I got back
smoke was coming out of the cowling. Turned battery switch off and removed cowling, the
alternator was super hot. Checked all the connections to ensure they was correct and they where.
Turned on battery switch to see what was going on and sure enough the alternator started getting
hot.

Has anyone heard of this happening before? I disconnected the lead to the alternator and turned
on battery switch and it no longer heats up.

The new battery was almost completely drained with in a few minutes. It was down to 30%
according to the charger.

Right now now looking at getting the alternator rebuilt at a local shop. Just want to be sure prior
to installing and potentially frying another alternator.

Thanks in advance.

[bassbama]

Is this a Mercury 150 4/S

[Fishstalker001]

Yes sorry. 150 4/S

[bassbama]

I have the same issue this may be a concern with this model engine and whoever the supplier to Mercury was for these alternators hard to say I have read a few instances on this site of alternator problems . My motor is seven years old so don't know if these are isolated problems or widespread. I know they are expensive to replace but they are not like or built the same as car alternators at 5500 rpm this thing is spinning at 16.5K so take that into consideration when making your rebuild or replace decision.

[bassbama]

Also if you launch the Mercury parts catalog and look up the part# for a replacement it has a superseded number hopefully the new model is of better quality.

[Fishstalker001]

I seen there was a superseded part number. At this point, I think it’s better to fry a rebuilt
one verses a new $300 one. Seems to be a lot of 150 alternator issues out there.

[bassbama]

I just talked with Mercury customer service and they said there was not a service bulletin out on that alternator for the 150-4S.

[ScottOz]

I know they are expensive to replace but they are not like or built the same as car alternators at 5500 rpm this thing is spinning at 16.5K so take that into consideration when making your rebuild or replace decision.

They are built the same as a car one. The issue most people see is they buy a "new aftermarket" (china) compared to the OEM.

[bassbama]

They are built the same as a car one. The issue most people see is they buy a "new aftermarket" (china) compared to the OEM.

Marine Alternator Features

Marine Alternators In order to meet these demands, alternators built for marine use have features not found in automotive-grade units:
Spark screens that meet U.S. Coast Guard standards to eliminate the alternator as an ignition source
Double-insulation to eliminate electrical shock in wet conditions and prevent sparks
Dual fans and large heat sinks for self-cooling under high, continuous loads
Stainless steel bearings, corrosion-resistant metals and heavy-duty coatings
High output at low RPMs to match marine diesel engine operating conditions
Battery sensing regulators for high-efficiency battery charging and detection of battery cell failure

[EuropeanAM]

They are built the same as a car one...

False statement, unfortunately. The "Car One" isn't built or intended to spin at 15,000 RPM's for extended periods of time.

I would strongly recommend sticking with the OEM (Mercury) Replacement unit.

[DQM]

Had the same issue. 2013 150 4S.

Had as a local,shop quote me to rebuild it, but when he was sourcing parts his supplier had a new one exact P/N available. $150 and had it the same day.

Always worth checking with local shops and seeing what they can do, often times cheaper than buying online.

if you are getting quotes for rebuilding it, or having it rebuilt, make sure they know it is a marine alternator and the shop does marine alternators.

[Fishstalker001]

I dropped it off at the shop for rebuild yesterday. Guy wasn’t sure if he could do it or not
but they are familiar with marine parts. I live on the Florida gulf coast so marine repairs are common.

Should hear something today. Buying a new one isn’t an issue, just rather fry a rebuilt one
instead, in case the problem originated elsewhere.

[Fishstalker001]

Just to update. Alternator shop could not repair the old one. Claimed they could not find
parts. Ordered new one, installed and op check good.

Thanks for for all the help