Engine Alignment Problems

[HenryTully]

Sir,

I am working with a boat yard with highly professional staff at a top yard trying to figure out why I have excessive vibration from my engine/shaft/prop when I reach about 7,500 rpm and above. I have a 2003 Sabre 402 with a Yanmar 4JH3E engine with a maxi prop. The engine was aligned to specifications (ie .003) and tested but no luck. I then had the boat pulled and the the prop cleaned and re-installed. The shaft was examined and was found to be ok. But I'm still experiencing excessive vibration after being put back inthe water. (The mechanic rechecked the alignment after the disappointing in water testing and found the alignment was acceptable.

Any advice on what can be the problem?

HTully

[theartfuldodger]

Just a thought but check the motor mounts I had a time when I mixed up the mounts and had a vibration, becuase I had put the wrongs ones in the wrong place. After I corrected it the vibration went away. Well you might say how is that, they are rated differently.

[capngregg]

Isn't this engine only rated for 3700 RPM max. continuous and 3800 max. crank speed? Unless you're running a 2:1 transmission that must be a typo at 7500 RPM.

Is it a saildrive unit or does it have a trans with a prop shaft/shaft log? I would suspect the shaft log is worn or if this is a folding /feathering prop, one of the blades is not un-folding or out of track.

The mounts are a strong possibility as well.

[HenryTully]

capng,

You're right. It's a typo. The engine starts the excessive vibration at 2,750 and up. The mounts are brand new and installed according to Yanmar's specifications. That is, 200 on the torque side and 150 on the other side. It's a frustrating problem to say the least.

Hank T

[HenryTully]

Artful Dodger,

The mounts are new and installed according to Yanmar specifications. It's frustrating to say the least.

Hank T

[Freesail99]

Is the prop new? Has it been changed ?

[HenryTully]

Freesail,

No, the maxiprop is 5 years old. It was removed from the boat, cleaned, inspected and reinstalled. The mechanic said it was in good condition.

HT

[capngregg]

I would take the prop to a prop shop and have them check the prop pitch, feathering mechanism and balance if you're sure the shaft is straight and the log is not worn out.

One blade at 1/2 of a degree off from the other blades will set up an unbelievable vibration.

[SEMIJim]

HenryTully,

We just went through the same ordeal with our 1976 Pearson 30, Atomic 4 engine and Martec folding prop. After much experimentation (and not a little gnashing of teeth!), I determined it had to be the prop. That was the consensus here on Sailnet, too. So we had the boat hauled, had the Martec folder swapped-out for the original Michigan Wheel fixed two-blade prop, and voila`: Problem solved!

If your engine/shaft alignment is good, prop shaft runout is good, and cutlass bearing is good, I would suspect the prop.

Good luck,
Jim

[fullkeel7]

I would agree with SEMIJim, it does sound like a prop problem. After visiting the maxiprop website and seeing all those blade indexing teeth, I seem to remember on the older props, it was quite easy to get a tooth off. Did the vib problem arise after the rebuild?