350 Mag Belt Slipping - 320 Sundancer V Drive

[skolbe]

History: The first season I had my boat I went for a cruise to a neighboring marina and bought fuel. Went to start the boat and the belt started squealing. The marina sent a mechanic down and tightened it for me. Great service. The water pump is the mercruiser bronze pump and the impeller has been replaced a few times.

The last 2 weekends when I start the boat after anchoring and the generator has been running for an hour or so, the belt starts squealing. It only seems to happen when the bilge is good and warm and sat for an hour, when I got back to the slip, I restarted the boat immediately and it was fine. Do you think it is the belt stretching and I should replace it or the water pump locking up? It eventually starts turning after I wrestled with the belt for a second (Engine Off).

 

[jason78]

It eventually starts turning after I wrestled with the belt for a second (Engine Off).

Do you mean to say the belt does not turn when the engine is first started?

Does the belt seem to be tight enough? Could be the belt or another belt driven device has a pulley bearing starting to go out causing the belt to rub on the inner edge of one of the pulleys.

 

[skolbe]

The belt does not turn, so you get squealing as it slips. Yet the belt seems plenty tight. Always happens when the generator has been running and heat has built up in the bilge while anchored. I do have the blower running with the generator running. Starts up cold just fine.

 

[jason78]

Strange. Sounds to me like a bad belt. Possibly before it was tightened it slipped too much and glazed the belt surface causing it not to grab the crank shaft pulley when it heats up?? When it runs, does it run true? If it does not wobble or vibrate and to don't have any weird bearing sounds, a new belt may be the way to go. You could always swap belts to test.

 

[skolbe]

It runs fine normally and everything is straight and no wobbling and or noises. I will replace the belt and start there.

 

[HUMPH]

So, I had the same issue with my 320DA but only when it was in escrow (she was pissed at me!). Once in a while, for that engine model, the last 1/2 revolution when shut off is backwards. That causes the impeller to turn the wrong way. Sounds strange but it does just that. I loosened the belt and verified I could not turn the pulley the correct direction but could the reverse direction. Simply grab the pulley (I wore gloves) and force it to turn the correct direction. There is not enough contact between the belt & the pulley for the engine to do this on its own. Snug the pulley back up and on you go.

 

[jetpartner]

History: The first season I had my boat I went for a cruise to a neighboring marina and bought fuel. Went to start the boat and the belt started squealing. The marina sent a mechanic down and tightened it for me. Great service. The water pump is the mercruiser bronze pump and the impeller has been replaced a few times.

The last 2 weekends when I start the boat after anchoring and the generator has been running for an hour or so, the belt starts squealing. It only seems to happen when the bilge is good and warm and sat for an hour, when I got back to the slip, I restarted the boat immediately and it was fine. Do you think it is the belt stretching and I should replace it or the water pump locking up? It eventually starts turning after I wrestled with the belt for a second (Engine Off).

The bearings in the seawater pump are going bad. Trust me I know it happened on both of my engines. They will seize and break the belt while under way. The engine will overheat very fast. Dont mess around anymore replace both pumps. This happened to me with same engine set up.

 

[Quint4]

Just to add to the conversation, there is a Mercury Marine Bulletin concerning misaligned pulleys and belt trouble on some Merc inboard engines.

http://www.mercruiserparts.com/bulletins/001/04/2003/EN_04.PDF

 

[skolbe]

I know Admin Scott had a similar issue at the beginning of each season with his 320 with his Port motor.