I have now learned that the belt on the sewater pump on my new 3YM30 Yanmar engine and other maufactured by Yanmar is 20" and is too long to be able to have enough tension to run the pump and the engine will overheat as a result. Anyone with a new Hunter boat with a Yanmar engine should be advised to check the tension on this belt and determine whether the correct belt was installed by Yanmar. Yanmar says that the replacement will be covered by the warranty. (I would hope so!)
3YM30 Yanmar factory defect
- Thread starter JohnEh
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John, I saw your other post about the your bad
belt tension. Honestly, and with all due respect,,,, this is 'shade tree', 'behind the barn', 'do it blindfolded' stuff. That spec you were given is the belt deflection at the center of the belt after it was tensioned. Knock on a Buddy's hull, who knows about this stuff and ask him to show you how to do it. And don't forget, this is an 'engine off' check. You need to learn this stuff otherwise the tow services will get rich on you.
belt tension. Honestly, and with all due respect,,,, this is 'shade tree', 'behind the barn', 'do it blindfolded' stuff. That spec you were given is the belt deflection at the center of the belt after it was tensioned. Knock on a Buddy's hull, who knows about this stuff and ask him to show you how to do it. And don't forget, this is an 'engine off' check. You need to learn this stuff otherwise the tow services will get rich on you.
Belt tension
Regarding belt tension: my opinion would be that both the alternator and the raw-water pump belts are just your ordinary everyday V-belts, just like on a car. So you just do them up as tight as you can get them without hurting anything, and don't worry any more about it. I used to have (really my Dad had, and I borrowed many times) a belt jack, which is a device you put between 2 pulleys to push (screw) them apart until you get the right belt tension. The idea is that you can then tighten down the adjustment bolt, with no time pressure, or worry about the tension changing. At some point, I decided I had to have one of these, since I loved doing it the "right way". So I was chatting with an auto mechanic about this, and asked him how he did it. His answer was: just stick a broom handle through the hole in the alternator bracket and pry the alternator up while you tighten the bolt. He never used a belt tension gauge, and I'd bet most mechanics don't either. I never could find a belt jack of my own, and I've just been using a broom stick ever since. So I think the answer is: it's just a V-belt, so get it pretty tight, tighten the adjusting bolt, and ... don't exactly forget it, but check it periodically to see if it seems reasonable. But don't stress about what the perfect tension is. Without a belt jack and a gauge, there's probably no way in the world to get the tension perfect. And I can tell you that the belt jack my Dad had would never fit between the 2 pulleys for the raw-water pump. If you could find one. Which I never did. (BTW: the marine diesel mechanic here in Annapolis who worked on our new 306 / 2GM20F said "Just try to turn the alternator pulley by hand. If you can't turn it, it's tight enough.") Jay
Regarding belt tension: my opinion would be that both the alternator and the raw-water pump belts are just your ordinary everyday V-belts, just like on a car. So you just do them up as tight as you can get them without hurting anything, and don't worry any more about it. I used to have (really my Dad had, and I borrowed many times) a belt jack, which is a device you put between 2 pulleys to push (screw) them apart until you get the right belt tension. The idea is that you can then tighten down the adjustment bolt, with no time pressure, or worry about the tension changing. At some point, I decided I had to have one of these, since I loved doing it the "right way". So I was chatting with an auto mechanic about this, and asked him how he did it. His answer was: just stick a broom handle through the hole in the alternator bracket and pry the alternator up while you tighten the bolt. He never used a belt tension gauge, and I'd bet most mechanics don't either. I never could find a belt jack of my own, and I've just been using a broom stick ever since. So I think the answer is: it's just a V-belt, so get it pretty tight, tighten the adjusting bolt, and ... don't exactly forget it, but check it periodically to see if it seems reasonable. But don't stress about what the perfect tension is. Without a belt jack and a gauge, there's probably no way in the world to get the tension perfect. And I can tell you that the belt jack my Dad had would never fit between the 2 pulleys for the raw-water pump. If you could find one. Which I never did. (BTW: the marine diesel mechanic here in Annapolis who worked on our new 306 / 2GM20F said "Just try to turn the alternator pulley by hand. If you can't turn it, it's tight enough.") Jay
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