Optimax 150 Alternator bolt sheared

brucehawsker · 21 February 2009, 10:07

The bolt (?s) attaching the alternator to my engine have sheared after 320 hours - 4.5 years. Should I be surprised? Given the bolts attaching the compressor failed last year, this says something about design - or am I being unfair given the strains and stresses on these parts in bad seas?

Ribshop · 21 February 2009, 10:29

Hi Bruce

This is a common problem and I have seen it a few times. There must be a manufacturing problem somewhere but as far as I am aware there is no recommended fix to stop it happening again. I would be interested to find out if anyone has come up with a long term solution.

Nasher · 21 February 2009, 10:29

Bruce hi.

I don't think you are being unfair at all, I honestly don't think it should be happening.

Is this something other Opti owners have experianced?
Because if so I think I'll avoid them in the future.

Nasher.

outboardtech · 21 February 2009, 10:46

thats interesting ? have you got the serial number at hand ?

jwalker · 21 February 2009, 10:48

It's not uncommon for alternator bolts to fracture. The cause is usually some out of balance force causing vibration of the alternator. It is not obvious because alternators are fixed pretty firmly so the vibration isn't noticeable. The two places to check are runout of the pulleys (including wear or unevenness of the belt surfaces) and unevenness/wear of the belt. If the belt isn't even in dimensions over its length, it will induce a cyclic vibration into the surfaces it is running over.

You might imagine an alternator would be made very accurately but I've personal experience of a new alternator with 17thou runout of it's main shaft! How it came to be it anyones guess.

It goes without saying that the alternator fixings should be tight. If the bolts are stainless steel, change them for normal high tensile ones. Stainless steel is poor at handling cyclic loading.

Edit: I thought I'd better mention; I've seen alternators fitted with superiour fastenings only to have their mounting brackets fracture because the source of the vibration was not addressed.

codprawn · 21 February 2009, 14:00

I have seen this problem cured on hotrods by using thick rubber washers to absorb the vibration. Sometimes too tight a bolt can be a problem!!!

brucehawsker · 23 February 2009, 20:21

Sorry dont have serial number accessible. Was new in autumn 2004. Dave Crawford reckons it was our driving and wave jumping! He is sorting it out - presumably drilling out the bolts and repalcing them....

Should I complain to Barrus?

Dirk Diggler · 23 February 2009, 20:26

Yeh, Tim Bennett is the man to speak to.

outboardtech · 23 February 2009, 22:05

the prob is how many years warranty did you get with that Opti . I think then in 2004 it was only two years or even three . Not sure if timmy B will warranty it for you . have a chat with him he is very helpful

tim griffin · 24 February 2009, 07:52

Hi Bruce
Had the same happen to me replaced the bolt and the bracket as that was also worn due to vibration , dont think its your driving think its just a common fault that could be addressed . Am changing engine at the moment to Mariner Opti 150 hp Longshaft so still have faith in the engines just will make it part of the service to check for wear and tear in this area .
Tim