Starboard engine problems/screaming

Was backing the boat out of boathouse today and the engine quit. With wind and outgoing current we managed to get her back to the slip with a few expletives to accompany our re-entry adventure. Predeparture checks were good..fluids, belts etc. Both engines were producing water after start. Once we got her back into the slip we opened up the hatch to see if we were spraying fuel or if there were any obvious signs as to why the engine stopped. Nothing was evident so I climbed down into the hatch and examined the belt again. No obvious signs of carnage. I asked my wife to attempt to start the engine. The noise that came with the cranking was hideous..like a loid scream.. All of the pulleys were spinning except the lower left pulley. I removed the belt and tried to spin it by hand. Got about a half inch of play but it wasn't going beyond that. Is that the water pump and is it a big deal to change?? This boat has been on the hard for 4 months and got new belts and hoses. Ran fine the day before but am perplexed as to why this would happen out of the blue?? Any thoughts or advice would be greatly appreciated!!!!

That is your raw water pump. It is difficult to spin the pulley, as the rubber impeller has a lot of resistance, but it should spin with some effort.

So either the serpentine belt is too loose and not providing enough tension to spin the pulley or the impeller is damaged and physically preventing the pulley from spinning.

I'd like to add to Espos4's comment.

The raw water pump has two bearings that also go bad. That would explain the screaming sound.

Thanks to both of you for your replies. Do you suggest replacing both so I don't go thru this again or just r/r the pump and belt so we can get on the water!!! Do you have any suggestions on best type of pump to put in?? Not impressed with MerCruiser products. Spent 14k+ on the hard two weeks ago and then this happens. Just want to get in the water already..lol!!

Normally these pumps are Jabsco pumps. They can also be rebuilt, so don't throw the old one away. You must have the capability to press the new bearing on

Something with the above theories isn't working for me. For it to "scream" as you say is something else, i.e. belt slipping. I would put belt on and start the engine again. Try to diagnose from there while you can actually see things turning or not. Have never heard of a raw water pump seizing up and a bearing going would give you notice. Especially since you had it running the day before and didn't notice anything at that point. Please report back as to solution. $14K on maintenance????? Ouch!

At idle it’s possible that a seized raw water pump could cause an engine to stall. I’d slack the belt and see if it starts and runs for a 10 seconds or so. If so, the engine is likely fine.

As has been stated, it’s likely a seized bearing in the pump. If the housing isn’t damaged or badly scored by abrasives, it can be rebuilt.

Me, I’d buy a new one and a pulley, install it, and have the failed one rebuilt for spare.

remember. If it has tires, tits, tracks, or trim tabs, it’s trouble.

The belt theory is easy to test. Start the motor and run some hard wax on the turning belt. It's a old trick. If it's the belt the sound will go away as the belt turns on the pulleys.

Don't run the engine to long, if that is the problem the bearing could seize. You also don't want to score the shaft or the pump. If that happens then the pump may have to be replaced. When mine failed I did buy a new pump and a rebuild kit as well. Good luck with it and keep us informed.

Thanks to everyone for the information. Had mechanic check it and it was the raw water pump. It had seized and the belt was screeching around the pulley. Old pumps were the mercruiser types. Pulled and replaced both pumps with the rebuildable, stainless steel ones I purchased from Fisheries. Working good now!!!