Hi All,
I have a vibration when driving my boat (2001 4.3L carb engine, alpha 1 gen 2 outdrive, 2001 21ft aluminum hull deck boat), that I'm trying to chase down, or determine that it is just "normal". This is my first i/o. This is my second summer with the boat, so I'm still getting used to it. I've never driven another sterndrive, so I don't have a baseline. (anyone live nearby Madison, WI?
). I can't recall if I noticed the vibration last summer, but it is really bugging me this year.
I feel like I've checked everything with the engine, so now I'm most curious about the rest of the driveline. Is there anything downstream from the flywheel that could be causing a vibration this that i should have inspected?
The vibration is most noticeable between 1000 - 1500 RPM, gets less noticeable as RPM increase, and seems to go away by 3000 rpm. I THINK the vibration is there at idle in neutral, but hard to tell, definitely worse under load, especially just off idle very noticeable. It feels to me like a dropped cylinder, but I think I've ruled that out. It is a very regular steady vibration. At low RPM, like 1200, the frequency of the vibration is almost the same as when a helicopter is flying over, and has a similar quality to it. If I have a fishing poll leaning over the side of the boat, the pole tip is definitely sharking with this vibration if I'm in gear just off idle.
I sat in a lot of GM cars with carbed 4.3 motors, and they were smooth as butter, no helicopter vibrations at low rpm. Of course this is a boat with solid engine mounts to an aluminum hull, without all the insulation engineering in to a car, so maybe this is just normal? If an experienced i/o owner told me it was normal, it would be annoying, but I'd believe it. It is right in the grey area of concern. However if I felt this much vibration in a car, it would NOT be normal, I can confidently say that.
Here are the technical background details:
Any and all ideas appreciated!
I have a vibration when driving my boat (2001 4.3L carb engine, alpha 1 gen 2 outdrive, 2001 21ft aluminum hull deck boat), that I'm trying to chase down, or determine that it is just "normal". This is my first i/o. This is my second summer with the boat, so I'm still getting used to it. I've never driven another sterndrive, so I don't have a baseline. (anyone live nearby Madison, WI?
). I can't recall if I noticed the vibration last summer, but it is really bugging me this year. I feel like I've checked everything with the engine, so now I'm most curious about the rest of the driveline. Is there anything downstream from the flywheel that could be causing a vibration this that i should have inspected?
The vibration is most noticeable between 1000 - 1500 RPM, gets less noticeable as RPM increase, and seems to go away by 3000 rpm. I THINK the vibration is there at idle in neutral, but hard to tell, definitely worse under load, especially just off idle very noticeable. It feels to me like a dropped cylinder, but I think I've ruled that out. It is a very regular steady vibration. At low RPM, like 1200, the frequency of the vibration is almost the same as when a helicopter is flying over, and has a similar quality to it. If I have a fishing poll leaning over the side of the boat, the pole tip is definitely sharking with this vibration if I'm in gear just off idle.
I sat in a lot of GM cars with carbed 4.3 motors, and they were smooth as butter, no helicopter vibrations at low rpm. Of course this is a boat with solid engine mounts to an aluminum hull, without all the insulation engineering in to a car, so maybe this is just normal? If an experienced i/o owner told me it was normal, it would be annoying, but I'd believe it. It is right in the grey area of concern. However if I felt this much vibration in a car, it would NOT be normal, I can confidently say that.
Here are the technical background details:
- Starts great
- Idles great and steady
- Good compression 150-152 all cylinders
- New plugs
- New wires
- verified spark at all cylinders (using timing gun to clamp each wire to check for strobe)
- Checked base timing is good
- Has the new version of ignition sensor under the cap
- Has new gimble bearing, replaced last summer
- 3500 pound deck boat, tops out around 40mph with just me in it. (I thinkt his seems right)
Any and all ideas appreciated!
