Prop vibration

[madhatter1]

Long story short. Bought boat in 2018. 2019 have new (and qualified) mechanic on board. Says I have a bad vibration on port side. Check cutlass. I do. Cutlass bearings needed and all replaced. Much smoother. Seems good to me. FF to this year. Haul out. Recondition props. PM. Splash. Trip home with same mechanic on board. Says the racors are shaking violently (they are). To me same old feeling on the bridge.

Haul out. Send shaft, coupling, and a spare shaft I was given out. Comes back spare machined to mate to coupling labeled as main, original reconditioned but labeled as spare due to wear around log area. Install with new cutlass bearings. Some vibration but need to wait to do new alignment for a week or so to settle. Did alignment and we actually dropped the engine front and rear 1/4”. Alignment to within 4 thousands.

Now you would think we would be good at this point. Still have vibration. I can feel it most standing over the strut in the cockpit. If I run higher RPM the racors stop shaking. Like at that RPM the vibration harmonic is lessened up at the transmission.

Which brings me to this question. Is the prop bad? Running 3 blade 28x25 pitch that started out square. I thought when reconditioned they would be balanced. Is the reduction in pitch from square too far? Am I better off with a new set of 4 blades? I want to fix this.

[osprey]

Vibrations suck. I only check / do my engine / shaft alignment in the water after a haul out.

Hope you solve your issue soon.

P