Buzz vibration throughout rev range

[Oddy]

Hi guys new to forum, I have a 2000 mod 23 Caribbean running a 5lt mercriuser with alpha 1 gen 2 Drive. Originally the gimble went and then the rear mounts, I replaced the rear mounts with new superseded ones and also used genuine gimble bearing, the engine line up is 99% perfect as my line up tool practically falls in, I am a HD fitter by trade and have purchased all the correct tooling to carry out these jobs but ever since I have done these jobs I have had a buzz style of vibration throughout the boat, I have even gone as far as fitting my mates alpha drive but to no avail. Have also fitted brand new Drive coupling geniune,Has anyone else had this issue.

Possibilities: Although the front mounts look fine have they failed
I did remove the flywheel and thought it only went back in one position could I have gotten that wrong
Harmonic balancer looks fine could this be an issue
With the new rear mounts the fibre washers do have slight interference between the belhousing and mount
base
Are the new mounts a harder compound than the old ones.
Any ideas would be appreciated, thanks in advance

 

[alldodge]

If the alignment bar goes in and out with 2 fingers then your aligned. To ensure the coupler is not misaligned, need to rotate the motor 90 degrees and insert the alignment bar again.

If this checks out, then need to make sure the issue is not the drive or prop. Remove drive and attach hose to thermostat housing to see if the vibration shows up. Without the drive on you can increase rpms without issue

 

[GA_Boater]

It could be something other than the motor, too. Putting it all together after yankin' the motor and outdrive, something could be vibrating like a seat or doghouse, maybe a hose touching something.

Check the tin flywheel shield between the oil pan and bell housing for loose bolts - That one will drive you up a wall.

 

[achris]

Hi Oddy and :welcome: to iboats.

Is that a 23' Crusader?

I suspect you're local... Any chance you would like a personal visit?

Chris...
(have MPI computer diagnostics)

 

[QBhoy]

What’s the prop like ? Although this would normally only cause a vibration at 2 stages in the Rev range. A vibration right through it would suggest it’s not a rotational issue or source.

 

[Oddy]

Hi guys thanks for the reply’s. I reside in Perth Western Australia, my Caribbean was a fly ridge model but I removed the fly bridge and then raised the roof 215mm this allowed me to put another fuel tank down in the galley floor we do big miles over hear and now with 320 litres on board I have a good range, the prop is a brand new 16 pitch stainless PT prop from the US but I have tried other Ali props as well to no avail it sounds almost like a gudgen knock but a lot finer, I have removed the sump and checked the mains and big ends they are all fine my oil pressure is approx 45 to 50 psi on the run and 25 at idle so no real issues there, I can’t get it to do it in Nutral only in gear, the Gudgen thing keeps coming back to me, I’m not sure if the 305 Chevy was prone to this or not, all other points that have been raised have been checked.

 

[Rick Stephens]

I've heard buzz noises from gimbal bearings and u-joints. those would be my first suspects.

 

[alldodge]

Alignment bar went in/out with 2 fingers
Rotated 90 degrees and alignment bar in/out with 2 fingers

Unless you have loose motor mounts I have no ideas left, hope someone else has one

 

[achris]

Hi guys thanks for the reply’s. I reside in Perth Western Australia, ....

Me too.