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496 ho serpentine belt

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badmedicine

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"My previous problem that stil

"My previous problem that still exists is with an alarm and guardian mode at 3500 rpms w no gauge action. i have noticed that the serpentine belt seems loose and there is black dust from it in the surrounding area. can a loose belt that is slipping affect that alarm as well as other things? if so does anyone have a schematic or know how to get one on the correct routing of the belt, what the individual pulleys are, what the tension should be on the belt? is it and adjustable tensioner and where that is. any help would help. thanks again carl"
 
"Do you have good battery volt

"Do you have good battery voltage, is your circulating pump or alternator siezing up? There should be a pulley with a nut and a smaller bolt head to adjust your belt, the belt should be pretty tight. My 383 would shut down to an idle when the fuel filter was plugged, have you checked yours?"
 
"Carl...

How loose is loose

"Carl...

How loose is loose? Is your belt so loose that the water pump isn't spinning fast enough and you're overheating? I know you said that the guage isn't going up, but maybe it's not accurate either. The belt should have about 1/4 to 3/8 inch deflection midway between 2 pulleys.

Wrench"
 
The only weak spot w/a serpent

The only weak spot w/a serpentine belt is the tensioner. They wear out by the spring weakening and losing some tension. Some fine belt dust is normal. If it is tensioned enough you should not be able to turn anything w/2 hands.
 
"Not to take issue; but normal

"Not to take issue; but normally there is no spring tensioner on marine serpentine belts. The tension is adjusted by an adjustable idler pulley normally located port side top.

The belt should be tight enough that you can't deflect it more than 1/2" at the longest run with moderate thumb pressure. If you can get more, it needs tightening.

Rod"
 
"Thanks for the clarification

"Thanks for the clarification Rod. Now everyone knows I own an "old" boat.
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"
 
"Well, Mercruiser does not use

"Well, Mercruiser does not use spring tensioners for serpentine belts, but Volvo does.

Anyway, Carl your problem has one possible tell tale, that is the fact that Gaurdian Mode takes place at exactly 3500 RPM. This typically means that the Shift Switch is misadjusted or faulty (the PCM thinks your in neutral). The PCM has a neutral overspeed function that is set for 3500RPM, and if it exceeds this RPM, you get an alarm and Gaurdian Mode. You should be able to check this by disconnecting the shift Switch, which opens the circuit and tells the PCM your in gear."
 
"Rod:

I did change the base

"Rod:

I did change the base gasket on my 4.3L and set the carb accel. pump on max. volume. Will be on the water today or next. Old gasket was postcard thickness; new one is 1/4 inch. Am I repeating myself? Better check myself in to the nuthouse for a checkup.
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"
 
"seems to me, depending on the

"seems to me, depending on the year of the motor, 'cruiser used a threaded rod on the alternator to tension the belt. it was on the earlier motors as i recall, as i'm not seeing them on the late model product. and clean the flame arrestor and check the iac muffler if equipped or you'll be dealing with iac issues before long"
 
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