Broken serpentine belt

[Dcdesign]

New boat owner. 2004 Monterey 248 passed down from father in law. It has the 350 mag MPI bravo 1 engine. He always had the yearly service done and it was just completed in February and I believe the belts were put on (they look new too), no cracks or wear. We’ve taken in out a dozen times in the last 3 months with zero issues...until today. Fired it up and had a bad squeal and then smoke and burning rubber. The belt had melted in half. All the pulleys seem to freely turn except the seawater pulley. I’m not sure if it should spin or not. Could the belt have bound up or got stuck on something??? I don’t think a pulley is bad. Any ideas and/or help is welcomed.

 

[achris]

Take the belt to a car parts shop and buy a Gates belt to replace it. No point paying Merc's 'marine tax' for something that you can get at a car shop.

The water pump will be stiff to turn, but you should be able to turn it by hand. If you can't, time for a service.

Chris.......

 

[Fun Times]

Check to see if the seawater pulley "Shaft" assembly moves in/out or side to side in any/all directions as the shaft should not Move Around besides turning the pulley in the normal turning direction when engine is running...Sometimes the pump assembly can come apart internally causing issues.

Another thought would be belt/pulley alignment...The following link info shouldn't be for your engine model but it's more of an how too reference for you if needed,
http://mercruiserparts.com/bulletins/001/04//2003/EN_04.PDF

What is the part number on the belt?

 

[Dcdesign]

The only thing I see on the belt is 57-865615-003

 

[Lou C]

Get an accurate straight edge like a level and lay it across the faces of the pulleys to check for proper alignment, make sure none of the brackets are bent.

 

[nola mike]

Get an accurate straight edge like a level and lay it across the faces of the pulleys to check for proper alignment, make sure none of the brackets are bent.

Melted rather than shredded. Guessing the water pump is your culprit.

 

[Fun Times]

The only thing I see on the belt is 57-865615-003

Model	CID / Cylinders	Year Range	Serial No. Range	Type of belt	Alternator / Water Pump Belt	Belt Length	Power Steering Belt	Belt Length	Sea Water Pump Belt	Belt Length

350 Mag BRAVO (RWC w / P / S)

350 / V-8

2002 - 2008

0M600000 & up

Serpentine

57-865615Q03 #18 #21 #23

2704 mm to inches = 106.456693

#'s
18 For engines with power steering.
21 For engines with standard cooling.
23 For engines with high mounted alternator.

• Length: 106.25"
• Width: 13/16"
• Gates # 6PK2705
• https://forums.iboats.com/threads/replacement-belt-size.744209/post-5660234

 

[Searay205]

my buddy had the same thing happen once. Not saying this is your issue but his alternator accumulated rust between the stator and rotor and siezed it.

 

[Dcdesign]

Melted rather than shredded. Guessing the water pump is your culprit.

That’s what I was thinking. But wouldn’t the pulley be locked up?

 

[Dcdesign]

Get an accurate straight edge like a level and lay it across the faces of the pulleys to check for proper alignment, make sure none of the brackets are bent.

I will for sure check that. Thanks for that

 

[nola mike]

That’s what I was thinking. But wouldn’t the pulley be locked up?

Yes. "All the pulleys seem to freely turn except the seawater pulley. "

 

[Dcdesign]

Yes. "All the pulleys seem to freely turn except the seawater pulley. "

It turned a quarter of a turn and then stopped. Not sure if it’s seized or if I didn’t turn it hard enough to spin impeller. But I don’t know that much about a seawater pump. From the diagram I found, it seems that motor has a seawater and water circ pump. So...trying to figure it out without having the call mechanic.

 

[Lou C]

Also wondering if the bearing for your seawater pump could be starting to seize up. The natural resistance of the impeller blades could mask that I guess.

 

[achris]

That’s what I was thinking. But wouldn’t the pulley be locked up?

Doesn't have to be 'locked up'. A high enough load can stress the belt to the point of breaking. And remember that the load increases as the speed increases...

 

[Dcdesign]

Also wondering if the bearing for your seawater pump could be starting to seize up. The natural resistance of the impeller blades could mask that I guess.

Someone else suggested that to me. It’s a really good point. Any idea how to determine?