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Author Topic:   135 optimax alternator bolt keeps breaking
skydude posted 06-08-2005 05:56 PM ET (US)   Profile for skydude   Send Email to skydude  
I have a 2001 135 optimax on a Dauntless and the bolt that attaches the alternator to the power head has sheared off 3 times already in the last 10 hours. Has anybody been having this problem, any solution? Thanks.
bsmotril posted 06-09-2005 07:49 AM ET (US)     Profile for bsmotril  Send Email to bsmotril     
There was an update on early model small block optis to replace the alternator mount bracket with a new design bracket. I'm not sure if your model yr engine already has it, or not. Best to check with a Merc dealer by providing him your motor serial number to see if the update is applicable to your motor. Barring that, I'd check the tightness of all the bolts on the bracket to be sure that the one bolt is not taking all the loading by itself and being over stressed in the process. BillS
skydude posted 06-09-2005 08:56 PM ET (US)     Profile for skydude  Send Email to skydude     
Thanks, the Merc dealer said he had checked the tightness of all the bolts and the tension on the belt..after the second bolt snapped after an hour of use.., he told me he installed a thicker bolt and it should hold. He said that it wasnt a Merc approve fix, but that he had done it a few times and that it had broke after 3 hours of use...btw, my 2001 135 Optimax has 550 hour of use..Thanks for the responce.
bsmotril posted 06-09-2005 09:08 PM ET (US)     Profile for bsmotril  Send Email to bsmotril     
Did they use the same grade/hardness of bolt as the original? Rather than going up in thickness, going to a higher grade bolt like ones used for cylinder heads (Grade 8 I think) might to the trick. I would also look very carefully at the hole in the bracket where that bolt passes through. Check for burrs, or ridges on the hole edges. Might even help to slightly bevel the edge. Any roughness in the bracket could set up a stress point in the bolt. Also make sure it is torqued to factory spec, and not over tightened which can weaken it. Something is wrong here as this is the first instance of this problem I've heard of after reading everything I can about Optis on the net over the past 8 yrs. BillS
Chuck Tribolet posted 06-09-2005 11:58 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
Here's a thread Google found:


skydude posted 06-21-2005 08:12 PM ET (US)     Profile for skydude  Send Email to skydude     
Thanks for the far I haven't had much luck, so far 2 mechanics refused to work on my engine, and a third wants to tear out my alternator have that checked and wants to open up my compresor....stay tune.
Chuck Tribolet posted 06-21-2005 08:16 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
Compressor????? Optimaxs have a compressor?????


bsmotril posted 06-21-2005 11:16 PM ET (US)     Profile for bsmotril  Send Email to bsmotril     
Yup,Optis have a compressor. It is made from the block, piston,and crank from one of the small Merc outboards with a different head with reed valves inside. It is belt driven off the flywheel and supplies the air pressure to blow the charge into the cylinder. Optis fuel injectors inject fuel into the air rail where a separate injector opens to let it into the cylinder. I think they run around 90 PSI. BillS
bluewaterpirate posted 06-21-2005 11:46 PM ET (US)     Profile for bluewaterpirate  Send Email to bluewaterpirate     
Ur right on the Opti PSI figure ...... That's where the difference is between the HPDI & Opti .... the HPDI fuel is drawn through the fuel pump and vapor separator, then pressurized by the twin high-speed fuel pumps to 1,000 psi in 250/300hp HPDI. The smaller block HPDI's fuel is pressurized to 900 psi.


oliviergomez posted 05-13-2007 04:55 AM ET (US)     Profile for oliviergomez  Send Email to oliviergomez     

I am located in Europe, my 135 Merc is also having the same issue. The bolt keeps breaking. Any final solution to that headache.Thanks in advance. Oliver

contender posted 05-13-2007 11:23 PM ET (US)     Profile for contender  Send Email to contender     
Check the number on lines on the bolt head the more lines the stronger the bolt, Go to a good hardware and ask for grade eight bolt try this...good luck
highanddry posted 05-14-2007 01:28 AM ET (US)     Profile for highanddry  Send Email to highanddry     
I suggest AN hardware. If you cannot find any let me know the grip, length and diameter and I will get you one if I have any.
jamesmylesmcp posted 06-24-2010 08:23 PM ET (US)     Profile for jamesmylesmcp  Send Email to jamesmylesmcp     
Had an issue like that last year.

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