Promax 300's snapping alternators off..

[waterboy222]

Had an issue last weekend that I thought was just a fluke..

I ran the boat all weekend with no issues, but when I got it home I pulled the hood of the starboard motor and the alternator was laying on top of the engine along with a lot of metal shavings and belt dust..

I cleaned everything up and was able to extract the broken bolt and put everything back together. I decided to check the Port motor and the SAME thing had happened..

So I chalked it up to maybe some repair work hadnt been tightened back down and went boating..

Ran all weekend this weekend and I noticed the SB motor miss a few times so I pulled into the dock and yanked the hood up.. SAME PROBLEM again.. SB motor sheared off the bolt and the Port motors bolt is bent enough that it would break on the next run..

Its the bolt that plays the part of the hinge, the adjuster bolts are fine. I replaced the bolts with 1/2" longer bolts becuase the others were REALLY shallow.

What am I missing here? Theres not a way to align it because they lay down horizontally instead of vertically.

Any ideas or experience with these situations? Heavier grade bolts? I dont want to put 8's in there and mess up the head..

[HighVelocity]

It's sounds like your missing something in this senario... Why all of a sudden is this happening...?? I mean if the bolts loosened up sure they can snap, but both sides...?

Is the boat drawing more current to cause this type of torque load?? I would make sure you don't have a short somewhere...

Are the bearings in the alternators locking up during a heat cycle???

Just throwing ideas at you....this is a strange one.

Ed

Ohhh last thought,,,how tight are your belts...because the newer motors have tensioners...I didn't think of that...don't over tighten the belts.

[NICE PAIR]

Are you running your belts to tight? I just use hand pressure to tension them. No prybars. :thumbsup:

[waterboy222]

I cant speak for the first episode of the problem, I just bought the boat and hadnt ever checked the alternator belt tightness.. But when I put them back on, I didnt prybar them in, I got them as tight as I could by pulling on them.. But even with that, it was still a pretty loose belt. I thought the first time was because the bolts were too shallow. They were shiney like they were new and had been recently replaced. Maybe I need to put a lock washer on there to keep them from backing out from the vibration, getting loose and snapping them? I didnt see it in the manual as having a lock washer on there though.

[waterboy222]

Mine dont have automatic tensioners on them, you just pull them in place and tighten the adjuster bolt down. And they ran 14v all day with no issue, i dont ever remember seeing it drop below that unless we were idling.. Its confusing..

[HighVelocity]

Mine dont have automatic tensioners on them, you just pull them in place and tighten the adjuster bolt down. And they ran 14v all day with no issue, i dont ever remember seeing it drop below that unless we were idling.. Its confusing..


If it's a new boat to you all bets are off... You can't really say what the last person did is correct. So, my advice would be to try and bring everything back to manufactures specifications...Bolts/hardware, Torque Spec on bolts etc. I would also use some BLUE locktite. I would also hope you are getting at laest 5 turns in on the bolts.

[waterboy222]

I may need to go to a tad longer bolt then.. I bought some locktite this morning so thats the next step...

[Gorilla0178]

I dont know if its a Merc issue or not, but i have a friend I boat with, and he called me up yesterday to take a look at his motor. Its a merc optimax 150, i know its not the same as the 300, but it had the same issue, broken alternator bolt and torn up belt, broke for no apparent reason, snapped clean off, alt. still turns freely so does the compressor. Now I work with a guy and he has opti's and he had the compressor lock up on him and it broke the mounting points right off the block, merc had to replace the block to repair it. I'll be sure to keep up with this thread.

[M. HARDEE]

May wanna go to a better grade bolt

[Gorilla0178]

I went to the Merc. Mech today to get a replacement bolt and belt for a friend, the guy behind the counter said that they had "fatigue issues" with the original bolts. They have a new one to replace it.

[M. HARDEE]

I went to the Merc. Mech today to get a replacement bolt and belt for a friend, the guy behind the counter said that they had "fatigue issues" with the original bolts. They have a new one to replace it.:eek::D:thumbsup: BETTER GRADE BOLT !!!!!!!!!

[waterboy222]

Sooo maybe i should upgrade to a 7 or 8 bolt instead of a 5.. I just dont want to mess up the threads! Im gonna try lock tight and a lock washer with a #5 this weekend and see what happens..

[WATERWINGS]

subscribed

[M. HARDEE]

Sooo maybe i should upgrade to a 7 or 8 bolt instead of a 5.. I just dont want to mess up the threads! Im gonna try lock tight and a lock washer with a #5 this weekend and see what happens.. WELL --- CALL ME A DUM-ASS--- BUT EVERYTIME U BREAK AND TRY ANOTHER BOLT YOUR WORKING THE THREADS OVER AND OVER ----THE quailty # of the bolt has nothing to do with the threads other than taking care of the problem. You ruin the threads by repeating the same mistake over and over .. WHY DON'T YOU JUST PUT THE BEST BOLT YOU CAN GET IN IT WITH WASHERS AND LOCTITE AND BE FINISHED. BEFORE YOU RUIN THE THREADS AND ALT OUR SOMETHING ELSE. -- not to mention broke down in the middle of the lake - AGAIN----- JMO. Mitch:cheers::thumbsup: PS ---ABOVE ALL ---PLEASE DON'T TRY YOUR THEORY WHEN INSTALLING THE STEERING BOLT , HELOCOPTER ROTOR BOLTS, WHEEL LUG BOLTS ,AIRPLANE WING BRACKETS , OR BRACKET HOLDING WIFES MOTHERS FAVORITE CHINA PLATE :eek::D

[waterboy222]

Merc part is a Grade 5 bolt. Thats where my theory of upgrading the bolt came from. I just have some concern about a $.10 bolt destroying a VERY expensive head. How are the threads getting hurt if its the top portion of the bolt thats snapping off?

[Gorilla0178]

Well I dont know where you got the .10$ bolt. Merc charges like 15$ for the bolt, talk about import fees from China.

[Gorilla0178]

Well i have another thought. The guy I work with at the boat shop has 175 opti's, I dont know what failed on his, but when it did it actually broke the alternator mounts off the powerhead, merc had to replace the whole block. I thought it was the compressor mounts, but it was the alternator mounts.

[M. HARDEE]

merc part is a grade 5 bolt. Thats where my theory of upgrading the bolt came from. I just have some concern about a $.10 bolt destroying a very expensive head. How are the threads getting hurt if its the top portion of the bolt thats snapping off?EVERYTIME you have to screw another bolt in those threads and tighten it over and over is what will take out the threads -- i would be putting ------------------------------------------------------------- A BRACE ON THE OTHER END OF THAT BOLT ----- if it was mine . But sounds like you got it figure out . Cheers

[lpugh]

The problem is not the threads or grade of bolt! The problem lies in that the bolt needs to be supported by another bracket at he head of the bolt that will not allow the bolt to be pulled sideways under load. Another words the bolt needs to go thru a support bracket, then the alternator and in to the block. The bolt will not break if it has the proper support.

[M. HARDEE]

The problem is not the threads or grade of bolt! The problem lies in that the bolt needs to be supported by another bracket at he head of the bolt that will not allow the bolt to be pulled sideways under load. Another words the bolt needs to go thru a support bracket, then the alternator and in to the block. The bolt will not break if it has the proper support.:iagree::cheers:

[gfinch]

The problem is not the threads or grade of bolt! The problem lies in that the bolt needs to be supported by another bracket at he head of the bolt that will not allow the bolt to be pulled sideways under load. Another words the bolt needs to go thru a support bracket, then the alternator and in to the block. The bolt will not break if it has the proper support.

I also agree! In worn threaded holes I like Time Serts

[Chaz]

It's called being placed in double shear ... ;)

My vote for best quote of the thread has to be .... >




OR BRACKET HOLDING WIFES MOTHERS FAVORITE CHINA PLATE :eek::D

[waterboy222]

Alright, I follered everyones advice and got the Merc bolt. Followed it with some blue locktite and a lock washer. Im not sure i follow the "needs a bracket" statement, I can't for the life of me figure out what bracket youre speaking of. It doesnt show anything like that in the manual.. Unfortunately we are in flood stage now here in Oklahoma so boating is shut down for the next couple of weekends while the debris clears out so i wont have an update as to if this fixed the issue or not..

[M. HARDEE]

you need to look in the MAKE A BRACE ---manual