Bama

I am seeing belt dust and I am thinking about changing belt. Probably the original belt on my 2003 496 mag ho W/200 hours that I purchased a year ago.

Does anybody really use that ridiculously expensive belt tension tool that mercruiser says must be used when installing a new belt?

When I got the boat there was a lot of belt dust in the flame arrestor and on the bulkhead in front of the motor. I replaced the impellor last fall and just tightened the belt till it felt right.

BUP

iTrader: (9)

Belt dust thru the flame arrestor is very hard on the piston rings as the flame arrestor is not an air filter, they suppress spark and or flame and do a very poor job of filtering incoming air into the throttle body and internally the motor. Also belt dust can clog the IAC muffler cavity as well. A lot of belt dust can be signs from rusted pulleys - belt adjustment too tight or belt alignment off or of course all 3.

Its wise to make sure you do not have a problem for the cause of excessive belt dust as it will lead into other problems over time. The biggest one also is breaking the belt and then you loose all cooling of the motor in a very short order. At one time mercruiser had 496 engines in the field that had misalignment of the pullys for the serpentine belt. They thought they had them corrected before they entered the market but did not as some miss the correction.

Sydwayz

iTrader: (1)

No. Just replace the belt and go with 1 finger width of deflection. If it's too loose, your water pressure is going to suffer as it's going to slip. (That's the hardest resistance pulley.) If it's too tight, it's going to jump off. You will find that out on the first outing.


FWIW, the later model 496s have automatic spring tensioners. You could convert it you wanted to.

Before you mess with the bolt tensioner on the alternator on your 496, make sure you use some penetrant on that tensioner unit. I have siezed and snapped that bolt off before. You are SOL until you get a new part at that point, and I don't know how many of those are still available anymore. GM and Mercury have EOL'd the original Camshaft Position Sensors on those early models. (To replace a Cam sensor, you have to change the whole front of the motor now.) Same could happen for other parts now that the original 496s are 12+ years old, and GM hasn't made 496 blocks in at least 4-5 years.

Bama

Thanks guys. no rust on pulleys. I gave the boat a thorough going over after I bought it and saw excessive belt dust. I cleaned the flame arrestor and I found an idler pulley with the bolt backed off almost all the way, could have been the cause of the excessive dust. Now after 50 hours since I corrected these problems I am seeing some belt dust but not nearly as much as when I first got the boat. I will try a new belt and see what happens.

BUP

iTrader: (9)

Mercruiser spec for Serpentine belts are to check deflection. The belt deflection should be measured on the belt that has the longest distance between 2 pulleys. the tool they recommend is from Kent Moore called the tension gauge. Of course others make them as well including gates, goodyear, dayton and so on.

Anyways if you do not have the tool - again checking from belt distance the longest between 2 pulleys should be with one figure in downward pressure on the belt with proper deflection of 1/4 inch or 6 mm. After tightening the belt the motor should be ran for a short period 10 to 15 mins and it is important to recheck the belt adjustment. Anyways the jist as how Merc teaches it.

fountain27ho496

Mine had what looked like belt dust the whole time I owned it. Think it may be common on 496. 12 years 800 hours original belt.