Engine: one adjusting bolt is loose

[Pavel24]

Hello,

I found out past weekend that one bolt for adjustment of the engine was lose .

The bolt is is the front starboard side. There 4 engine mounts in total.

Engine is Volvo MD7A ( no sail drive)

Boat is in the water

how am i best to proceed ? i guess the bolt need to be adjusted correctly with the shaft .

i will continue my research on this subject .

[Pavel24]

i will just go and buy feeler gauge and adjust the shaft

[a64pilot]

Feeler gauges are nice, but not needed really. A butter knife, hacksaw blade etc will work fine. You adjust to get it as close as you can. A set of feeler gauges will just put a number on it, but if it’s as close as you can get it, then it’s as good as you can make it.
You need a set of gauges anyway to adjust valves, I recommend a set of “go-no go” gauges, they don’t require as much experience to use.

Just know that it can be done without feeler gauges.
Apology if you already know this
https://www.wonkeedonkeetools.co.uk/...-feeler-gauge/

[Pavel24]

thank you, i didnt purchase the tool yeat.

I found this https://www.yachtsurvey.com/Alignment2.htm

what i am thinking is :

3 of 4 adjusting bolts are still in place
my cutless bearing isnt new ( in good shape)
the motor mounts look to be in good condition

what i am trying to understand if i adjust the loose bolt under the motor and just tight it will it be much worst then trying to adjust the motor to the shaft in a tight space with used cutless bearing

[Lepke]

Don't be lazy, do it right. I do my alignments within .002". I've seen all kinds of damage from people assuming their alignment was ok. Including ruining a transmission, or shaft and strut damage, etc.

[a64pilot]

I think you need to tighten the nut and check alignment.
Your linked article is actually correct, but it’s not just vertical and horizontal alignment, it’s actually angular alignment that is most important. If I’m saying that correctly, the system cannot self align to compensate for that.
By that I mean it’s important to ensure the engine isn’t cocked off to one side as in say the front of the engine has shifted left a little or the front is too high or low.
Think of the coupling connection being your wrist, your wrist has to be straight it can’t be bent.
The system cannot correct for that. Only a CV joint or similar can account for that.
I sort of gave up, because in truth the only way the systems can truly work is of the engine is solidly mounted, and you don’t want that due to vibration and noise.
I installed a Brunton’s Sigma drive. Not to take anything away from it, but it’s simply a Rzeppa joint, which has been around for a very long time, a Rzeppa joint differs from a regular universal joint in that it is actually a constant velocity joint and nearly vibration free, and accomplishes that in a single unit.
With the Sigma drive the engine should be allowed to float around a little alignment wise without inputting any stress into the system.
Alignment should no longer be an issue.

In truth and I’m sure I’m going to get some argument on this, but for a long unsupported shaft to actually run true with no vibration, it needs some bend.
Long tail rotor driveshafts on Bell 206 helicopters have a bow in them, you can stretch a string to prove that.

Take a long piece of steel wire like a long gas welding rod and chuck it in a drill and spin it the end in your fingers of course you’ll see it whip, put a little bow on it and it will run true.
The 206 had “Thomas couplings” or disk assemblies to allow misalignment, I believe the Sigma drive will do the same.

[Pavel24]

Thank you , i will do it right . I just didn't grasp how to adjust the right angle of the shaft to motor but if i understand correctly, it should already be aligned and all i have to do is adjust the angle of motor in alignment with the shaft (i don't touch the shaft) .

[Q Xopa]

Originally Posted by Pavel24

Thank you , i will do it right . I just didn't grasp how to adjust the right angle of the shaft to motor but if i understand correctly, it should already be aligned and all i have to do is adjust the angle of motor in alignment with the shaft (i don't touch the shaft) .

Correct, you align, ie move the adjustable mounts, under the motor to the propeller shaft. The Propeller shaft is your 'reference' you are moving the engine to.

The angular alignment A64 is referring to is what is measured with feeler gauges. Or as has been mentioned a hacksaw blade etc. The object is to get an even distance between the coupling faces top to bottom and left to right. This should get you shafts parallel.

But your feeler gauges dont actually measure if the shafts are parallel but not on the same axis (co axial), shaft eccentricity. Hopefully your coupling bolts and holes keep this close enough.

However the feeler gauge method wont correct for an eccentric or angular misaligned couplings, or a bent shaft. So there is scope for error there.

The article linked was quite good. However the author is obviously not a fan of dial gauges. He was saying that a precession surface table and V blocks was the correct way they need to be used. This is correct if you are trying to measure a singular shaft as you need that accurate referance.

However when we have two shafts we simply connect our dials to the opposite shaft. It is a common industrial, aviation etc method.

IMNSHO it is far easier, quicker and more accurate. You can also see shaft eccentricity, shaft bend, coupling eccentricity or coupling angular misalignment. These reading take a little moving around of the indicators. Honestly only usually done if suspected issues. It never gets done with the regular feeler gauge method.

You also only need 3 readings, usually top and sides. Bottom not required like feeler gauge method. The bottom is usually the most difficult to access.

The readings are also 'live' so you can see how far to adjust as you are making the adjustment. So you just wind the mount to correct number on your dial (mid point of your reading). Ie set dial to 0, wind shaft 180 deg. Say your reading is 0.020", simply wind your mount to 0.010" for lateral. Go back to 12 o/c halve that reading for vertical. Do it in the near near (ie adjust nearest mounts (aft) looking at nearest (fwd) Dial), far far sequence and your done.

As opposed to adjust, check, readjust, recheck etc.

But thats just me, I know feeler gauges are the way it is mostly done. Thats fine, Im not trying to tell anyone how they should do anything. Obviously feeler gauges are cheaper than Dial gauges and shaft clamps. Most guys I mention DTIs to roll their eyes. But the guys that have done it with me are always amazed why everyone is not doing it.

Just my 2c.