Alternator bolts snapping

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unforgiven11B
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Alternator bolts snapping

Postby unforgiven11B » Sat May 12, 2018 6:19 pm

Third time in 2 months, (21.6 hrs) since last time. Engine is a 2007 Pleasure Craft Marine 6.0L. Based off an LQ4. Belt tension is good not to tight I can twist belt with two fingers. Grade 8.8 bolts last time they had two bolts holding alternator on and bolt keep snapping. Only tightening to 35-40ft lbs due to them going in the aluminum head. Last 2 times they snapped off clean with the head. This time only one broke before I noticed it and it broke off with 1/4” of threads sticking out. Alt spends free and smooth and don’t sqeak thought maybe bearings were seizing up and causing it but it seems just fine. Any of y’all know what’s going on? I am planning on getting a belt 3/4” longer and seeing if maybe it’s too much tension still. Any ideas on stronger bolts? Last ones were 8.8, maybe they are too hard? Bolts are not bottoming out either they have 1/8-1/4” of depth left once bolts are tight.
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Re: Alternator bolts snapping

Postby hdsadey » Sat May 12, 2018 6:53 pm

8.8 metric are like Grade 5 SAE. Next step up is 10.9, more like Grade 8 in standard. Might cure your problem.
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unforgiven11B
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Re: Alternator bolts snapping

Postby unforgiven11B » Sat May 12, 2018 7:03 pm

Have one 10.9 here will pick other up Monday. thank you for the info on that. Had no idea there was a difference.
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Re: Alternator bolts snapping

Postby skinnypockets » Sat May 12, 2018 9:25 pm

Curtis, Is there any kind of brace or support on the back side of that alternator? I'm not familiar with that engine but it seems to me there should be more support than just those bolts.

My phone died and I lost your number so give me a call when you get time. Rich

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unforgiven11B
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Re: Alternator bolts snapping

Postby unforgiven11B » Sat May 12, 2018 9:51 pm

Rich, I do apologize for the photos. There is a “C” Shaped cast bracket that the left lower bolt goes through and bolts to head. The higher right side bolt is longer and goes through alternator then bracket then into head. alternator has second bolt at top of C bracket to keep it secure . Bad design as both mounting bolts are lower than the center of the tension on the alternator pulley.
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Re: Alternator bolts snapping

Postby ladyblackwater » Sat May 12, 2018 10:20 pm

This is a VERY common trait with their motors. You need to call Pleasure craft and ask them for the support brace that cradles the alternator. I don't care what grade bolt you put in they will keep snapping. I've had to fix plenty of them.
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unforgiven11B
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Re: Alternator bolts snapping

Postby unforgiven11B » Sat May 12, 2018 10:33 pm

LadyBlackwater, the fist time it happened after going to Diamondback and speaking with one of the guys he told me it was a known issue as well and to call PCM, I did spoke with fellow who acknowledged the issue and asked for the SN on my engine gave it to him and he said that my engine model was not one of the problem engines with the bracket they changed. No idea what his computer was telling him, Obviously it’s a problem. Do you happen to know a part number? Would like to FIX the issue permanently not patch it till it breaks again.
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Re: Alternator bolts snapping

Postby unforgiven11B » Sun May 13, 2018 11:15 am

Through parts catalogs was able to determine the bracket used on my Engine year model was R090269. Have not found the other type yet. IIRC when speaking with PCM I want to say he said they used 2 brackets. I will give I call to them tomorrow and order the other bracket. LBW will this change the belt route or is it just a more stable bracket? Thanks for all the help
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Re: Alternator bolts snapping

Postby ladyblackwater » Sun May 13, 2018 12:51 pm

Unforgiven it will use the same bolt pattern on the alternator but gives it move stability (bracing) of the alternater. I have one in my shop but it's for the 8.1 (496). If they don't help you than get ahold of me and I'll help you out the best I can.
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Re: Alternator bolts snapping

Postby unforgiven11B » Mon May 14, 2018 10:30 am

Apparently PCM no longer has tech or customer support to help the product owners ....called twice today to speak with someone and the damn receptionist said they will only talk with a dealer now no public sales or service and she would Be Happy to give me a number to a dealer. Back in March I spoke with a guy there no problems.
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Re: Alternator bolts snapping

Postby ladyblackwater » Mon May 14, 2018 1:50 pm

That's some bull crap. My question is why do they go to shows trying to sell their product when you have to go through a dealer for their motors? Nothing pisses me off more than having a product of someone's and you have to go through a 3rd party when there is a problem.
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unforgiven11B
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Re: Alternator bolts snapping

Postby unforgiven11B » Mon May 14, 2018 4:09 pm

I took the boat to a pcm dealer/airboat manufacturer, they have never seen my pulley set up. I did see the new way it is braced and hoping he can order that if its available. Did say the belt is too tight so I will get a new belt 1-2” longer. I’m wondering if I can change this entire pulley system or alt bracket to something more available? Would a kit from summit or jegs work? I know I can’t go to a low mount alt like new engines my block is not taped is one location. I can’t see
Why any LS alternator bracket won’t work unless I’m missing something?PCM and dealer states it’s just a LQ4 long block.
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Re: Alternator bolts snapping

Postby ladyblackwater » Mon May 14, 2018 9:05 pm

Yes you can use different mounting brackets if they fit. If I'm not mistaken the high pressure pump is on the same side as the alternater. If it is you might have a problem using a different bracket set-up. Can you post a picture of what you have so I can maybe help you out on what you can do?
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Re: Alternator bolts snapping

Postby unforgiven11B » Mon May 14, 2018 9:52 pm

In the picture from the parts list my mount is identical however there is in idler pulley in place of the raw water pump. As I cannot find anything else close to my set up as well. I will get front cage off tomorrow and get better pictures if needed. You are correct the low pressure and fuel control cell are on that side and may prevent me from using an after market kit.
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Re: Alternator bolts snapping

Postby One Eyed Gator » Tue May 15, 2018 7:25 am

Curtis have you tried stainless bolts? They are softer tend bend some before they break. My old caddy was breaking grade 8 bolts went to a softer bolt and it would at least bend before it broke. also make sure the mount doesn't have a bur or something not allowing the mount to sit flush.

Do you know what spacing the accessories are - Truck, Fbody or Y-body
Kind of looks like truck spacing, but your pump has different inlet and outlet locations. If it is, one option would be to set it up like stock truck.

Or look at the https://sites.google.com/site/sloppywik ... alternator
I have done 4 motors this way and never had a problem. Also made a brace from head to back of F-body alt. mount.

If it is corvette/y-body spacing Smuggler on here sells the bolt and alternator kit. It is cheap if you already have the alt.

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Re: Alternator bolts snapping

Postby unforgiven11B » Tue May 15, 2018 2:07 pm

Mike, My apologies for not calling you back got busy and forgot, To answer your question no I have not used a softer bolt yet. Today went and got grade 12.9 socket cap bolts and a belt 1-1/2'' Longer in circumference going to give them a try. It had a belt 72-3/4'' on it and tensioner was maxed out and had no flex. Now Alt seems to have a lot less side pressure on it. I will run as is and keep close eye on it when or if this arises again I will drill and tap block fir Low mount option. I believe PCM told me it was truck spacing as its a LQ4 truck base and was never used in a car.
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Re: Alternator bolts snapping

Postby ringneck » Mon May 21, 2018 11:54 am

Common issue with PCM alt. bracket bolts.
Fixed mine (350 hrs.ago) . Only problem I ever had.

My bracket had a spare hole near the fuel control cell.
Surprised to find an UNTAPPED corresponding hole behind it into the aluminum head .

Tapped head, installed new bolt, problem solved.

Now I've got four bolts holding the alternator and it no longer has the leverage to stress /break the original three.

Sorry I didn't post my fix sooner. Hopefully others may consider this application as a preventative measure.
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