Saildrives and loose bolts

[MattS]

Looking for views from others on the following:

I have a question about engines with a saildrive and in particular Volvo Penta. The saildrive is connected to the engine using a number of bolts.

Has anyone ever heard of these bolts coming undone of their own accord?

If you have a saildrive, do you check them regularly or as part of your regular servicing?

I’ve heard about someone whose engine nearly suffered a catastrophic failure as a result of these bolts coming loose without him realising. The engine was fitted new in 2018 by a professional firm. They are now blaming the owner for not regularly checking the bolts! One of the bolts severed and half of it was found inside the engine!

 

[Slowtack]

No... But I am struggling to release the saildrive oil drain screw... Last opened about 3 years ago...

 

[Martin_J]

I didn't want to damage the slot on the drain plug.. Blocked the screwdriver up from underneath so it couldn't slip..

 

[Martin_J]

I read the OPs story somewhere else.

Hard to understand how a sheared bolt could even get to be inside the engine.

A severed bolt sounds like the result of overtightening anyway, so how would checking for loose bolts have found that?

 

[William_H]

I read the OPs story somewhere else.

Hard to understand how a sheared bolt could even get to be inside the engine.

A severed bolt sounds like the result of overtightening anyway, so how would checking for loose bolts have found that?

No can't understand how any part of bolt could get in to engine. However any loose bolt can give more load on other bolts allowing movement and fatigue. Had a similar thing with wheel nuts on trailer wheel. One nut loose leads to failure of studs. ol'will

 

[MattS]

Thanks @Martin_J @William_H - I have asked the same question on some other forums too, so you may have seen it there. Agree it's a bit mind-boggling!

Would you consider checking the bolts for looseness to be a regular task on an annual service etc.? I've certainly never checked those attaching my traditional gearbox to my engine...

 

[Tranona]

Simple answer to their claim is to point to the section of the workshop manual that gives the torque for the bolts and then the section on maintenance that makes not mention of any requirement for regular checks of the bolts.

This will be a claim under the Consumer Rights Act which requires the claimant to show that the defect was there at the time the engine was installed. Just within the normal time limit of 6 years and such cases usually end up with 2 sets of experts facing each other (metaphorically). So your friend needs to get his expert to examine the failure and produce a report arguing that the failure was due to either defective design (unlikely), materials (possibly) or workmanship. The claim is against the installer in the first instance so easier to get workmanship as defective material will require some involvement with Volvo.

Obviously there may well be more issues but this is based on the limited information available.

 

[vyv_cox]

By far the most common cause of failure in bolts is fatigue due to undertightening. The fracture is commonly at right angles to the axis of the bolt, which will not be deformed otherwise.
Overtightening may lead to plastic deformation, giving the bolt a waisted appearance each side of the fracture

 

[Martin_J]

Although for one bolt to shear at right angles, wouldn't that only happen if all the others were loose and allowed the two engine parts to move?

As to a bit found in the engine... Do these threaded holes go all the way through into the engine interior, or are they blind?

 

[Daydream believer]

On the Volvo D1-30 they go right through to the flywheel. If bolts are 5mm too long they will jam the flywheel & prevent rotation. So do not use the old bolts from your md 2020 in your brand new d1-30 . So when the man from Volspec comes to commission the engine that you installed yourself, he will find that it will not turn over as locked solid by the bolts. This will take a couple of hours to solve & cost you another £250 for an extra visit with the correct new bolts all 5 mm shorter.
Experience is a. Wonderful thing
I assume all the similar sized Volvo engines are drilled right through as well

 

[vyv_cox]

Although for one bolt to shear at right angles, wouldn't that only happen if all the others were loose and allowed the two engine parts to move?

As to a bit found in the engine... Do these threaded holes go all the way through into the engine interior, or are they blind?

View attachment 166682

Yes, it would be unusual for only one loose bolt to fail with all the others tight. But if they are all a little loose in this case the one with the higher cyclic stress due to being slightly looser would fail first and the others may be on their way.

 

[penberth3]

....Would you consider checking the bolts for looseness to be a regular task on an annual service etc.? I've certainly never checked those attaching my traditional gearbox to my engine...

I'd say weekly not annual, checking for loose bolts should be a regular task. It's basic preventive maintenance. I'd hope you do a bit more than dip the oil and press the button?

 

[MattS]

I'd say weekly not annual, checking for loose bolts should be a regular task. It's basic preventive maintenance. I'd hope you do a bit more than dip the oil and press the button?

Well I don’t have a saildrive, but no I don’t check the bolts holding my engine together regularly and no one I know has ever suggested I should! (Or mentioned that they do it themselves…)

 

[Thistle]

I spend half an hour checking the engine and drive of my car for loose bolts every time I nip to the shops - not! It's very rare for something that has been put together properly with the correct washers, thread sealant, etc to become loose let alone fail. If it does happen my first point of call is whoever worked on it last.

 

[vic008]

There are other bolts on boats besides on engines. Are they prone to also loosening? Engine vibrates, but wood to wood doesn't. Or perhaps everytime you use a bolt you should use a springwasher?

 

[Slowtack]

I didn't want to damage the slot on the drain plug.. Blocked the screwdriver up from underneath so it couldn't slip..

View attachment 166669

Thanks for the reply... I ended up using a bottle jack to keep the bit from slipping out of the screw head... A Phillips head would be a whole lot better in this application..

 

[Daydream believer]

Thanks for the reply... I ended up using a bottle jack to keep the bit from slipping out of the screw head... A Phillips head would be a whole lot better in this application..

I suspect part of the trouble was too small a screwdriver. Mine fills the entire slot & because the head is in a recess there is nowhere for the screwdriver to slide to. A slot is much easier to clean the old paint out. In addition one would have to obtain a larger headed philips screwdriver as a standard one would be too small.
But if alternative wanted, perhaps buy a 10mm socket headed bolt so you can use an allen key.

 

[ChathamSailor]

I'd say weekly not annual, checking for loose bolts should be a regular task. It's basic preventive maintenance. I'd hope you do a bit more than dip the oil and press the button?

There are a large tranche of boat owners who work full time and do not have the luxury of living near their boats, in yester year an employee or boat club staff might be available for such weekly checks, sadly this is no longer the case and such a regulatory of checking may be desirable but impractical.

 

[Beneteau381]

I'd say weekly not annual, checking for loose bolts should be a regular task. It's basic preventive maintenance. I'd hope you do a bit more than dip the oil and press the button?

That sounds like an ex forces regime! A story making the rounds was about such a thing, they used to do stuff like this ( not necessary by the way) and they used to wear the heads of the bolts and eventually overtighten them because the torque wrench operators always went a touch further than necessary.

 

[ChathamSailor]

I guess if you are on an MOD vessel you aboard every day, the wear and tear is very high, and the MOD pays for replacements, very different if you have to foot your own bills and work full time to pay for it all. I guess it’s all about safety within a sensible protocol.