Bore measurement Bravo bearing hole (vibrations/loose bearing)
06-04-2021 | 04:11 AM
#1
Thread Starter
Registered
Joined: Nov 2013
Posts: 34
Likes: 7
Bore measurement Bravo bearing hole (vibrations/loose bearing)
A lot of text coming, bare with me! I tried to keep it concise on the point.
I have a humming sound and vibrations when turning so I thought I start out by replacing the gimbal bearing. When I had punched it in (with the original tool) and was in the process of aligning, the bearing came loose by just cocking the alignment tool. I thought, that's not right! But circumstances forced me to go ahead with the install so I punched it back in. After reading a few threads with similar problems of loose bearings in the transom shield, I thought I would measure the hole in which the bearing sits. Does anyone know the bore or have ha new shield to measure? Measuring up/down/left/right (12/3/6/9 o'clock) should give a good average reading? I think it would be a good reference for the forum aswell, since the problem doesn't appear to be unique.
And some backstory to adress the original problem with the humming and vibrating: I just bought the boat with this fault, the previous owner says it's been like this for at least 4 years. He had the drive coupler replaced "a couple of years ago" and that eliminated the problem temporarily but now it has returned and he didn't want to deal with it.
- I can tell the transom assembly has been replaced not long ago, it's in really good condition visually (whereas the drive is a total mess, one of the worst corrosion cases I've seen)
- The hole in which the bearing sits had som scoring on the bottom entry. I felt it when the new bearing was in place, so I don't know if there are any other irragularities further in causing the bearing to sit loose. Will check this off-season when I can take it apart again.
- When putting the alignment tool in Without the bearing in place, I measured the difference of the gap between the alignment tool and transom hole with a flat en screwdriver, and it's off-center sideways. On one side the screwdriver went in and through, but on the other side I couldn't even get it in the gap. My guess is that the correction would need to be about 3/16" / 0.19685" / 5 mm.
- With the alignment tool sitting in the coupler without the bearing in place, I can rock the tool up/down/sideways quite a bit, but my friend who was with me said that the tool don't, and shouldn't, sit snuggly in the coupler but should have some play. I could rock/wiggle it around about 0.4" / 10 mm at the end of the tool where the handle is. Hard to explain, hope someone undertands
.
- According to previous owner, there's no vibrations or sounds when going straight (I will know Monday when I launch it and take it for a spin)
- The front engine mounts one each side are bolted down with the adjustable oval holes one the mounts both placed backwards. Is this really correct? Shouldn't the oval holes be placed on the opposite sides of each other to allow for the engine to be moved a little from side to side? (I could be totally wrong, I can't seem to work my head around the fysics ). Like it is now, the engine's sideways position is fixed because the non-adjustable round holes on the mounts on each side are bolted faceing forward. Plus, the bolts sits in the outer position of the oval holes on each side so there's no way of moving the engine sideways like it is now.
One of my guesses is that the problem is caused by a sideways misaligned engine and/or a loose sitting gimbal bearing. If the bearing hole actually is damaged/worn, it might be the engine misalignment causing imbalance on the bearing, which then creates excessive wear in the hole. Any thoughts on that theory, or any suggestions where to start? :/ (I made good pictures to illustrate the above problems but can't figure how to attach, I've tried both JPG and PNG)
I have a humming sound and vibrations when turning so I thought I start out by replacing the gimbal bearing. When I had punched it in (with the original tool) and was in the process of aligning, the bearing came loose by just cocking the alignment tool. I thought, that's not right! But circumstances forced me to go ahead with the install so I punched it back in. After reading a few threads with similar problems of loose bearings in the transom shield, I thought I would measure the hole in which the bearing sits. Does anyone know the bore or have ha new shield to measure? Measuring up/down/left/right (12/3/6/9 o'clock) should give a good average reading? I think it would be a good reference for the forum aswell, since the problem doesn't appear to be unique.
And some backstory to adress the original problem with the humming and vibrating: I just bought the boat with this fault, the previous owner says it's been like this for at least 4 years. He had the drive coupler replaced "a couple of years ago" and that eliminated the problem temporarily but now it has returned and he didn't want to deal with it.
- I can tell the transom assembly has been replaced not long ago, it's in really good condition visually (whereas the drive is a total mess, one of the worst corrosion cases I've seen)
- The hole in which the bearing sits had som scoring on the bottom entry. I felt it when the new bearing was in place, so I don't know if there are any other irragularities further in causing the bearing to sit loose. Will check this off-season when I can take it apart again.
- When putting the alignment tool in Without the bearing in place, I measured the difference of the gap between the alignment tool and transom hole with a flat en screwdriver, and it's off-center sideways. On one side the screwdriver went in and through, but on the other side I couldn't even get it in the gap. My guess is that the correction would need to be about 3/16" / 0.19685" / 5 mm.
- With the alignment tool sitting in the coupler without the bearing in place, I can rock the tool up/down/sideways quite a bit, but my friend who was with me said that the tool don't, and shouldn't, sit snuggly in the coupler but should have some play. I could rock/wiggle it around about 0.4" / 10 mm at the end of the tool where the handle is. Hard to explain, hope someone undertands
.- According to previous owner, there's no vibrations or sounds when going straight (I will know Monday when I launch it and take it for a spin)
- The front engine mounts one each side are bolted down with the adjustable oval holes one the mounts both placed backwards. Is this really correct? Shouldn't the oval holes be placed on the opposite sides of each other to allow for the engine to be moved a little from side to side? (I could be totally wrong, I can't seem to work my head around the fysics
). Like it is now, the engine's sideways position is fixed because the non-adjustable round holes on the mounts on each side are bolted faceing forward. Plus, the bolts sits in the outer position of the oval holes on each side so there's no way of moving the engine sideways like it is now.One of my guesses is that the problem is caused by a sideways misaligned engine and/or a loose sitting gimbal bearing. If the bearing hole actually is damaged/worn, it might be the engine misalignment causing imbalance on the bearing, which then creates excessive wear in the hole. Any thoughts on that theory, or any suggestions where to start? :/ (I made good pictures to illustrate the above problems but can't figure how to attach, I've tried both JPG and PNG)
Last edited by rokj; 06-04-2021 at 04:19 AM.
06-04-2021 | 06:12 AM
#2
Thread Starter
Registered
Joined: Nov 2013
Posts: 34
Likes: 7
Skimming through the Mercruiser owners manual for fun, I actually found a section for the engine mounts. The slotted holes should be facing forwards to allow sideways adjustment of the motor. Makes sense, it allows the motor to kinda rotate around its own centre with the fixed rear holes of the mounts still being fastened. So that answers that, but would still like some input on the the other thoughts!
