Shredded serpentine belt...again

msballin

msballin

Member
May 30, 2008
259
Islip Terrace, Long Island
Boat Info
2000 340 Sundancer
Engines
Twin 7.4L Horizons w/ Hurth V-Drives
So...here we go again. While just underway and throttlin up to 3200 rpms I smell rubber burning and hear a "roar". I look back and see white smoke from my port exhaust. Immediately shut engine down as the needle on the temp guage hit 225. Water was flowing fine from side exhaust while warming up prior to departure, coolant level was perfect (I never leave the dock without checking all fluids). Arrived back on starboard engine and discovered serpentine belt shredded. Upon inspecting this morning (engine way to hot to get near yesterday) all pulleys seem fine. Raw water pump replaced two years ago and had only 60 hrs on it. Mind you, this happened just two years ago and the culprit was the plastic tensioner pulley. New pulley was installed along with belt and alternator. Kinda stumped here as to what may have happened. Mechanic to visit this Thursday. Though my curiosity has me spinning. Any thoughts? Thanks as always
 
might want to check the bolts that secure the pulley to the harmonic balancer....sometime they work loose and let the pulley wobble while the engine is running which can eat belts.....also rust on the pulleys will abrade the belt over time....if there is rust take a steel wire brush and remove the rust....a light coat of paint on the pulley once the rust is removed would not hurt....

cliff
 
CliffA said:
might want to check the bolts that secure the pulley to the harmonic balancer....sometime they work loose and let the pulley wobble while the engine is running which can eat belts.....also rust on the pulleys will abrade the belt over time....if there is rust take a steel wire brush and remove the rust....a light coat of paint on the pulley once the rust is removed would not hurt....

cliff
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Thank you. Will check. As I'm not an engine guy (though I do understand a bit about them) I'm thinking the harmonic balancer is connected directly to the main engine shaft? If so, I'm also thinking it's not common to be able to move this pulley as it is "spun" by the engine running. Thanks for your reply. Much appreciated.
 
Ididntdoit said:
is the circulating pump or alternator siezed
Click to expand...
If you're referring to the raw water pump, its pulley is turning. Alternator pulley turning as well. Both were changed October 2015. Recently had work done on the starboard engine to include barnacle buster treatment to the cooling system. What's the likelihood some of this solution would up on the port belt and ate into it? Thanks for your help thus far. Greatly appreciated.
 
Ididntdoit said:
correct - attached directly to crankshaft - you wont be able to move it by hand
Click to expand...
Thx. That's reassuring. I'm able to move the pulley attached to the main water pump on the engine and can hear coolant inside the housing. All other pulleys are moveable as well. I mentioned in a response to "Ididntdoit"...
"If you're referring to the raw water pump, its pulley is turning. Alternator pulley turning as well. Both were changed October 2015. Recently had work done on the starboard engine to include barnacle buster treatment to the cooling system. What's the likelihood some of this solution would up on the port belt and ate into it? Thanks for your help thus far. Greatly appreciated." Your thoughts? Thx.
 
msballin said:
Thx. That's reassuring. I'm able to move the pulley attached to the main water pump on the engine and can hear coolant inside the housing. All other pulleys are moveable as well. I mentioned in a response to "Ididntdoit"...
"If you're referring to the raw water pump, its pulley is turning. Alternator pulley turning as well. Both were changed October 2015. Recently had work done on the starboard engine to include barnacle buster treatment to the cooling system. What's the likelihood some of this solution would up on the port belt and ate into it? Thanks for your help thus far. Greatly appreciated." Your thoughts? Thx.
Click to expand...
...correction to prior response..."wound up on the port belt..."
 
msballin said:
If you're referring to the raw water pump, its pulley is turning. Alternator pulley turning as well. Both were changed October 2015. Recently had work done on the starboard engine to include barnacle buster treatment to the cooling system. What's the likelihood some of this solution would up on the port belt and ate into it? Thanks for your help thus far. Greatly appreciated.
Click to expand...

There are two pumps. There is a sea/raw water pump and there is a circulating pump.
 
If everything is moving freely it is most likely caused by a pulley that is either wobbling or out of alignment.
 
Yes..both pulleys are turning freely...can hear coolant moving around while turning the pully on the circulating pump. Thx
 
Check that plastic pulley that was just replaced. Maybe on backwards or forgot the spacer
 
Just checked pulleys again. Idler pulley has approx. 1/16" wobble and spins freely. Alternator and circulator pump pulleys spin freely. Raw water pump pulley does not spin freely, though I am able to turn it with some force while feeling some resistance. Is this normal? Thx.
 
Should be no wobble. If you have wobble, then you may well have found your problem.
Idler, circulator, and alternator all have little internal resistance and should feel like they are spinning freely.
The impeller in the raw water pump is a very tight fit so it will be tight to spin that pulley.
 
JVM225 said:
Should be no wobble. If you have wobble, then you may well have found your problem.
Idler, circulator, and alternator all have little internal resistance and should feel like they are spinning freely.
The impeller in the raw water pump is a very tight fit so it will be tight to spin that pulley.
Click to expand...
Excellent! Thx very much. Will report back after mechanic visits tomorrow evening. Greatly appreciate all of the input!
 
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