ALIGNING ENGINE TO PROPELLER SHAFT
avatar

It is recommended to check the alignment once/year as the rubber in the engine feet ages.  Another reason for misalignment can  be that the locking nuts came loose.

Signs of misalignment :

  • Vibrations
  • Wear on cutlass bearing’
  • Leaking stuffing box
  • Loose bolts in shaft coupling

Center the shaft in the stern tube:

Engine should be aligned to the shaft.  Not the opposite!  To do that you need to fix the propeller shaft in the center of the stern tube.

A common way fixing the shaft  is with the use of 4 small wedges.  On an HR 43 it is not easy to get down to the shaft tube with both hands.  Holding 4 wedges in place and at the same time moving the shaft back and forth takes more than two hands.  Two persons in the engine room is not an option.

I had a workshop do a fixing tool in delrin.    (Drawing Shaft plug)

Fixing tool

Fixing tool

Shaft fixed in the stern tube.

Shaft fixed in the stern tube.

With the tool, it was easy to center the shaft in the shaft tube.  Even if you are not considering doing the alignment yourself,  I recommend that you carry the tool onboard.  The mechanic will most probably not have the tool, and try to do the job  anyway.  If the shaft is not fixed and centered, it is a risk that the shaft will be aligned to the engine instead of the opposite.

Align engine to the shaft!

Make sure you have the necessary tools to loosen the nuts on the engine mounts.  A crowbar can be handy when you have to move 200 kg engine sideways.

You can start with just eye baling the alignment.  Move the engine around until it looks good.  

When it looks O.K., it is time to measure.  Turn the shaft coupling around and  measure the distance up and down and on both sides between coupling and flange for gearbox with a feeler gauge. When it is whit-in 0.005 mm it is O.K.

Centaflex is a flexible coupling.  In the documentation it is said to be able to take up two degrees misalignment.  The local Centaflex dealer did not agree about that statement, and recommended to do the alignment as good as possible.

If you end up to high on the bolt for the engine mount, there will be more vibrations and load on the bolt.  It is recommended that you can see at least 5 mm thread on top of the locking nut.  If not you should put shims or pads between the mounts and the engine foundation.

Need to install a higher aluminum block under the engine mount. On the to do list.

Need to install a higher aluminum block under the engine mount. On the to do list.

If your boat has an Aqua-Drive unit it is important to know that you should not have perfect alignment.  With an Aqua-Drive you should have app. 2 degrees misalignment!  If not the bearings will not be lubricated and will wear out.

 


Comments

ALIGNING ENGINE TO PROPELLER SHAFT — 3 Comments

  1. Roland,
    Is your fixing tool only for hr43 or also compatible with hr40 ?
    I see you enjoy your Greece trip 😉
    Our plan is Croatia then Greece in the next years, for the time being we continue to stay in Côte d’Azur and Corsica !
    Laurent
    HR40-112

    • Hi Laurent,

      Yes, I´m sure the 43 & 40 have the same diameter shaft and the same diameter shaft logg.

      We are leaving Greece in August and are going to spend time around the Aeolian islands before we head to Malta for the winter.

      Have a good summer

      Roland

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.