Bukh dv 24 flywheel bolt fail
- Thread starter europe172
- Start date
Boater Sam
Well-known member
Sorry, but as an engineer I would not use that flywheel or crank and I am amazed that anyone with engineering knowledge would.
I do not see how they could accept the elongated holes, the torn threads or the damaged mating surfaces and centre locating spigot damage.
Does the flywheel run true?
I do not see how they could accept the elongated holes, the torn threads or the damaged mating surfaces and centre locating spigot damage.
Does the flywheel run true?
RivalRedwing
Well-known member
europe172
Active member
Measured at 4 places a gap to a fixed point are 18thou, 22thou, 36thou and 29 thou
So not sure what to make of that
Boater Sam
Well-known member
If that is face run out on the crank end its appalling. But with that surface damage I cannot see how you could measure anything at all.
ean_p
Well-known member
If you accept that your current bolts are the correct spec, that they are metric and assuming that they are not 'specials' then you should find a number stamped into the rim around the socket on the top of the bolt. This is indicative of the tensile strength and the yield point of the material.
This should enable you to order the bolts you need ( bearing in mind that if HT then often the thread is a finer pitch than standard metric bolts) I've just had a quick look and 'Unbrako' brand bolts at 12.9 for M12 x 45mm are around 80 pence from a place like this...... Unbrako Socket Head Cap Screws – Metric Self Colour Grade 12.9 | Product categories | Bolt World | Page 4
If your bolts are unmarked or of a lesser tensile rating then don't be tempted to 'up' the rating as the level of tensile strength is a matter of calculation and in some cases more is not always better then less in some applications.
Blueboatman
Well-known member
If the thing fails again the boat will be out of the water anyway
I would return it
Period
I would return it
Period
europe172
Active member
That is the run out at the Flywheel face about 70% of the radius
Boater Sam
Well-known member
I hate to upset another boater, but its all scrap sir.
Get it replaced under guarantee.
europe172
Active member
The value of the forum is that you get a range of advice , all food for thought
europe172
Active member
The replacement bolts I used are Umbrako made to DIN 912 standard
Blueboatman
Well-known member
I wonder if this motor has been back before ?? 
europe172
Active member
As an update, the engine has run for 15 hours with no problems, the engine supplier has agreed a replacement engine should one be required as a result of the flywheel bolt fail. We have agreed to review options in three months and between us take a decision as to the best course of action.
Many thanks to everyone who contributed
Many thanks to everyone who contributed
penfold
Well-known member
Without knowing what the usual run-out is at that point on an undamaged engine the measurement doesn't reveal much, there's no particular need to have a flywheel precisely machined as long as it is dynamically balanced, probably along with the crank. 18 thou is a bit less than half a millimetre.
Last edited:
Blueboatman
Well-known member
Well that all sounds both fair and responsible doesn’t it ?
Let’s hope you get trouble free sailing (and motoring ! ) from here on in.