Vibration on a drivetrain between 1100 and 1600rpm

[jean-marc tardif]

I just bought a 2004 42ft with twin 6cta, zf 2801-v transmissions.

I have launch the boat yesterday and I can feel a vibration. Between 1100 and 1600 rpm,

When the rpm is in the vibration range I can see the engine shacking a little bit more than the other side. Before launch I haven’t took measurement of the shaft but the Prop look good, no bend or dent.

Is there a pro here that could help me how to diagnose this?

Boat is in the water presently, would like to do all can be done in the water before hauling out

Thanks

Topic

[jean-marc tardif]

It’s shaped like a rust mushroom, exhaust was leaking sea water right on it. I’ll replace both on my next trip to the boat

[Rob Schepis]

jean-marc tardif wrote:

The gear stick

So it’s normal? Not because the breather is rusted stuck?

What is normal is to have a working breather vent to vent the pressure from the hot gear and then when it cools down you get the slight vacuum affect. Is your vent rusted or “rusted shut” ?

[jean-marc tardif]

Yes it’s a thru-hull exhaust but it’s not the case, port is normal and starboard get a vibration.

[glenn111]

Is it thru-hull exhaust. Can cause some vibrations being felt as it gets up on plane.

[jean-marc tardif]

The gear stick

So it’s normal? Not because the breather is rusted stuck?

[Rob Schepis]

Dipstick on the gear or on the engine? The gear stick will give a pressure noise but it’s actually vacuum.

[jean-marc tardif]

I bought a repo during winter, couldn’t test it, I took a chance. And frankly, it was a good one, the rest of the boat is awesome.

I haven’t disconnected the driveline yet to check for alignment, will do the next time I’m back at the boat. Will also bring the tools to test the engine mount. ( i live 1000 miles from where the boat is presently, not easy to bring a 4 foot prybar?

Just a thought, I have pulled the dipstick to check the quality of the oil and there was a lot of pressure, the breather is rusted shut. Can this cause the vibration?

[Rob Schepis]

Check the alignment at the coupler – being in the water now is the time.

Check the engine mounts that they are structurally sound and nothing is loose. Get good eyes on them and do a backdown test too.

Post some pics of the engines, the mounts and the driveline.

That’s a start…

You “just bought” the boat ? ….. Wasn’t it just surveyed and sea trialed ?

[Author]

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