Help ID what's screeching on my Merc 3.0?

OR Boater

Recruit
Joined
Mar 21, 2014
Messages
3
Used the boat for a bit the other day, the engine was warm, no problems. Shut it down for a few minutes, started up again, and noticed something odd: The charging voltage was low, as was the oil pressure. I opened the throttle a bit, in gear, and a horrible screeching noise comes from the engine. Not quite a belt sound, but something like it. Put it in neutral, opened the throttle again, same sound. Headed back to the marina at idle, with no noise. Once I was sitting just off the dock, I opened the throttle up again, engine sounds fine at any RPM. Oil pressure & voltage are fine. Shut it down for awhile, started it back up, noticed the same low voltage/pressure issue, opening the throttle causes screeching again, my son sticks his head in and says it sounds like it's coming from near the starter. I was thinking water pump based on the sound, but I guess the water pump on this is actually in the lower unit?

A couple facts that may be completely unrelated:

1) Earlier that day, my son had accidentally turned the key to start while the engine was already running.
2) I seem to have some water leak which I have not yet located, I think it is coolant water since it seems to be warm water collecting in the bilge, and I don't have many thru-holes to suspect.

Any tips to lead me in the right direction? Sorry, I'm pretty new to boat engines.

Kelly
 

thumpar

Admiral
Joined
Jun 21, 2007
Messages
6,138
There is a water pump in the drive and on the engine. The one is the drive is the sea water pump and the one on the engine circulates within the engine. To me is sounds like the engine circulating pump but you will need to find out where it is leaking.
 

flipbro

Master Chief Petty Officer
Joined
Feb 8, 2013
Messages
830
My guess is alternator. Check belt tensions they will make that noise when belt loose or when going bad.
 

fishrdan

Admiral
Joined
Jan 25, 2008
Messages
6,989
Also, remove the belt and spin the alternator to see if it spins freely with no rough feel/sound, same thing for the engine's water pump.

A mechanics stethoscope can help pin-point the noise, or a 3' section of heater hose held up to your ear and pointed at suspect points on the engine. I've even used a loooong screw driver as a poorman's stethoscope before, hold the handle against your ear and touch the tip against various points on the engine (no hair or appendages by fast rotating parts......)
 

tkat1000

Cadet
Joined
May 10, 2015
Messages
25
sounds like the starter drive gear could be hanging up on the flywheel. aka) starter solenoid is stuck
 
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