Ok, I have a 96 Merc 7.4, with Bravo III drive. Unknown service records as I bought this boat used, one year ago.
I have a rattling sound with a slight vibration coming from the drive. I have replaced the gimble bearing twice, but the sound is steadily getting worse, so it's not the bearing. My u-joints look and feel absolutley perfect. I've tried getting them to show any sign of play in any direction, but nothing. They are free moving with no roughness. There is no leaks in the bellows to have allowed water to reach the gimble bearing or u-joints. There is absolutely no rust on anything inside the bellows. Could the u-joints still be the problem?
When on the water this rattling sound can be heard idleing in gear while turning full port or starboard, and when trimmed as high as the trim limit and higher. With the drive straight with the keel, I only notice it when fully tucked under for takeoff, or when trimmed up high for bow lift to run at speed. If the drive is in neutral, the sound is still there with sharp turning, just not as noticeable.
Also, while I have had the drive off, I turned the props and noticed I can move the props a little in each direction before the input shaft/u-joints start to move. Is this normal? Are the gears inside the drive meshed tightly to allow no free play, or should there be a bit of play between the props and input shaft?
I'm planning to go on and put new u-joints in this weekend as I have already spent the $$$ on the gimble bearing, I might as well throw a little more money into the u-joints, and have them for peace of mind if nothing else.
I'm just looking for other opinions or ideas as to what I might look for as far as other unseen problems. At this point, I am assuming it is the u-joints, even though I can't obviously tell that they are bad. After new u-joints this weekend, and another test run, I guess I'll know a little more. If the u-joints don't fix it, it's going straight to a Merc dealer because entering the drive, is above my knowledge. Even if I had a truck load of manuals, and a wheel barrow full of specialty tools, I wouldn't be confident of putting everything back together right! :%
I have a rattling sound with a slight vibration coming from the drive. I have replaced the gimble bearing twice, but the sound is steadily getting worse, so it's not the bearing. My u-joints look and feel absolutley perfect. I've tried getting them to show any sign of play in any direction, but nothing. They are free moving with no roughness. There is no leaks in the bellows to have allowed water to reach the gimble bearing or u-joints. There is absolutely no rust on anything inside the bellows. Could the u-joints still be the problem?
When on the water this rattling sound can be heard idleing in gear while turning full port or starboard, and when trimmed as high as the trim limit and higher. With the drive straight with the keel, I only notice it when fully tucked under for takeoff, or when trimmed up high for bow lift to run at speed. If the drive is in neutral, the sound is still there with sharp turning, just not as noticeable.
Also, while I have had the drive off, I turned the props and noticed I can move the props a little in each direction before the input shaft/u-joints start to move. Is this normal? Are the gears inside the drive meshed tightly to allow no free play, or should there be a bit of play between the props and input shaft?
I'm planning to go on and put new u-joints in this weekend as I have already spent the $$$ on the gimble bearing, I might as well throw a little more money into the u-joints, and have them for peace of mind if nothing else.
I'm just looking for other opinions or ideas as to what I might look for as far as other unseen problems. At this point, I am assuming it is the u-joints, even though I can't obviously tell that they are bad. After new u-joints this weekend, and another test run, I guess I'll know a little more. If the u-joints don't fix it, it's going straight to a Merc dealer because entering the drive, is above my knowledge. Even if I had a truck load of manuals, and a wheel barrow full of specialty tools, I wouldn't be confident of putting everything back together right! :%
