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Correct Belt Tension

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BroJames

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2014 Mercruiser 5.7 350 MAG Bravo, single serpintine belt: how do you know when you have the correct tension, is it by feel, sound, or do you take a measurement? Appreciate the help, I am an amateur mechanic
 
Doesn't it have a self tensioner? Spring loaded idler pulley? If not you should find an area on the belt that is a straight shot for at least 12 inches, and move it with your fingers up and down. It should have 1/2" play.
 
From service manual

Proper tension - 15-19 mm (5/8-3/4 in.) deflection, with moderate thumb pressure, on
the belt at the location that has the longest distance between 2 pulleys.
 
The absolute best way is with a belt tension gauge!

I dont think they specify it in ounces or pounds of deflection only in mm/inches
 
timguy said:
Doesn't it have a self tensioner? Spring loaded idler pulley? If not you should find an area on the belt that is a straight shot for at least 12 inches, and move it with your fingers up and down. It should have 1/2" play.
Click to expand...

Why don't you know if it has a spring loaded tensioner like Automotive?

Shouldn't you have Mercruiser service manuals at the ready?
 
....Per manual..........
 

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There is not a spring loaded pulley. There is a pulley with a little cog/gear that sets the tension, sorry I have omitted that. The belt is too tight now
 
Right, Jack. I don't work on these as much as you, I am just suggesting that self tensioners could find a good application in Marine. That way we would always be assured proper tension. It's likely already been applied on some IO's that I haven't had my hands on yet.
 
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