Alternator Keeps Seizing!

[Allmand]

Hello again,

I have a 1968 GM 250ci 160hp l6 with Mercruiser M drive. I keep having issues with the alternator seizing up, getting the belt hot, causing it to burn the rubber which in turns is causing the belt to slip and the water circulation pump to not circulate which ultimately leads to overheating the hell out of my inline 6. Thank god for cast iron. If it were an aluminum block I would be looking for a new motor. Heated it up pretty bad, but still runs good.

The first time, I ran the engine hot twice after realizing it was the alternator completely seized. I put a new alternator on and all was good for a few boat trips. Overheated again last weekend with lots of burnt rubber smoke. I was afraid it was the coupler but I started with the belt. Took the belt off and the water pump moves freely, went to the alternator and again, frozen. Turns if you put your back into it but you can tell the bearing are gone.

I am NOT using marine grade alternators. I know I know. But they want so damn much for them. I am using the oreilly auto parts store alternator. Could this be the problem? Even if its not marine grade, shouldn't it last longer than a month? Could I be tightening the tension on the belt too much causing too much tension on the alternator pulley? Also, there is a large amount of black powder on the alt pulley, I assume from the burning belt.

 

[jopes]

Re: Alternator Keeps Seizing!

oreily = junk rebuilds. In fact not many rebuild shops build a good one these days.

Go on ebay, look for your alternator, bet you can get a marine version for not much more than what you paid for your one you have now.

btw, your risking your boat and life with that auto alt and not the proper marine version.

 

[Technorunner]

Re: Alternator Keeps Seizing!

its not impossible that you tightening the belt to much. on longest part of the belt you should be able to twist it about 90 degres. So if you twist the belt towards you, you should be able to get the small teeth towards you.

 

[Allmand]

Re: Alternator Keeps Seizing!

oreily = junk rebuilds. In fact not many rebuild shops build a good one these days.

Go on ebay, look for your alternator, bet you can get a marine version for not much more than what you paid for your one you have now.

btw, your risking your boat and life with that auto alt and not the proper marine version.

Yeah, you are right. I will spring for the marine one. I just hope that the only rubber that was burning and not the coulpler. God I would hate to have to go through that. Thanks for reply.

 

[Fordiesel69]

Re: Alternator Keeps Seizing!

The orielys,autozone, advanced auto, etc rebuilds are not even rebuilds. Just cleaned and resold with a nice warranty. I refuse to buy them anymore for anything good that I own.

Plain and simple the bearings were bad to begin with.

 

[fishrdan]

Re: Alternator Keeps Seizing!

You shouldn't be seizing multiple alternators, so I would look closely at how tight you have the belt tensioned. I used an automotive alternator on my 140 before I knew better and it worked fine, though I did replace the front bearing every couple of years as it was getting noisy.

You can get an inexpensive (China knock-off) marine alternator from DBelectric for $60-70. I've been running one for 1-2 years now and it works fine. I'm sure it's not the quality of a true Delco marine alternator, you get what you pay for....

Do you still have your old marine alternator? You could run it down to a local rebuilder and have them repair it. If it's just locked up you could pop it open and replace the front bearing, about $5-10 for that bearing.

 

[Fordiesel69]

Re: Alternator Keeps Seizing!

I always rebuild my marine starters and alternators and if necessary use automotive components only where they are NOT marine specific. Example: a rotor or bendix assembly.

 

[NetDoc]

Re: Alternator Keeps Seizing!

If the alternator is seizing, why not just put in a pair of high quality sealed bearings on the shaft? If my memory serves, there are only three for GM alternators of that era: 200, 202 or 303. Add an "SS" after any of them to get the stainless sealed versions of each. It might take 20 minutes to change the bearings once the alternator is off and then you KNOW what's in it. BTW, replace the brushes and integrated reg while you're in it.

 

[Fishermark]

Re: Alternator Keeps Seizing!

I certainly echo what everyone has said about the need for the marine alternator.

But you also should check and make sure your pulleys are all aligned correctly. I don't know if the alignment would cause the alternator to seize... but with the problems you are having, it would be wise to check.

 

[Allmand]

Re: Alternator Keeps Seizing!

Thanks for the replies. I think you are all correct. I tightened the hell out of the belt when I put the new crappy alternator on, so maybe too tight on that, on top of it not being marine grade. I am buying a rebuilt marine alternator on ebay for about the same amount I paid for this one...so hopefully this solves my overheating and burnt rubber smell......


thanks again.

 

[generator12]

Re: Alternator Keeps Seizing!

Hey bud, everything the guys said about using marine grade stuff on this thread is true. But your problem is belt tension. Marine grade or not, the bearings should not seize - even with pulley misalignment - with proper belt tension. Is this a flat belt, or a vee?

If it's a vee, adjust that tension for about 1/4 inch of play per 1 foot of belt length between the two farthest apart pulleys. If it squeals, tighten it up a bit, but only until you have the minimum needed to quiet it down.

 

[stackz]

Re: Alternator Keeps Seizing!

Thanks for the replies. I think you are all correct. I tightened the hell out of the belt when I put the new crappy alternator on, so maybe too tight on that, on top of it not being marine grade. I am buying a rebuilt marine alternator on ebay for about the same amount I paid for this one...so hopefully this solves my overheating and burnt rubber smell......


thanks again.

sounds like you answered your own question with the belt tension. too much side pull on the pulley will end that front bearing quickly.

though, depending on how "universal" you went with the alternator, it might not have an internal voltage regulator and if you are setup with an external voltage regulator on that old 1968 setup, it could be bad and the voltage isnt being regulated properly from the alternator causing it to spike more than less and overheating it and causing failure. might be something to look into.

 

[Silvertip]

Re: Alternator Keeps Seizing!

And since you have overheated the engine on more than one occasion, why not make sure your temp gauge and alarm are working properly and perhaps take a peak at them periodically. That simple process may save you an engine rebuild.

 

[Allmand]

Re: Alternator Keeps Seizing!

Hey bud, everything the guys said about using marine grade stuff on this thread is true. But your problem is belt tension. Marine grade or not, the bearings should not seize - even with pulley misalignment - with proper belt tension. Is this a flat belt, or a vee?

If it's a vee, adjust that tension for about 1/4 inch of play per 1 foot of belt length between the two farthest apart pulleys. If it squeals, tighten it up a bit, but only until you have the minimum needed to quiet it down.

Its a vee....and when I tightened it, I tightened so hard I used a long open end wrench to wedge between the engine block and the alternator to tighten it as much as possible. I always thought the tighter the better, although that statement still hold true for other situations (winkwink) I see it does not on a belt. So this time I wlll make sure I have that 1/4 inch of play. And use a marine grade. Thanks!

 

[Allmand]

Re: Alternator Keeps Seizing!

And since you have overheated the engine on more than one occasion, why not make sure your temp gauge and alarm are working properly and perhaps take a peak at them periodically. That simple process may save you an engine rebuild.

Yeah, I have rewired most of the stuff on the boat, but there has been so many re-wirings and old un-used wires left in place its like a rats nest. I know I should pull all wiring and start over. But I have replaced all of the main wiring and went through the main wiring harness to check and make any repairs needed. I think I have a grounding issue withthe instrument panel...so I have been using one of those laser thermometers to keep check on temp. But eventually I will rewire the entire panel. Always something to re-do.

 

[cr2k]

Re: Alternator Keeps Seizing!

Too tight on the belt will not only ruin your alt but your circulation pump brg as well. Also look for a short or some sort of load problem causing your alt to overheat trying to produce too much current. If you are using a 38 amp alt that will not be hard to overload. Should use at least a 55a of higher.

 

[Allmand]

Re: Alternator Keeps Seizing!

Too tight on the belt will not only ruin your alt but your circulation pump brg as well. Also look for a short or some sort of load problem causing your alt to overheat trying to produce too much current. If you are using a 38 amp alt that will not be hard to overload. Should use at least a 55a of higher.

Sorry, but what is "brg"?

 

[NetDoc]

Re: Alternator Keeps Seizing!

Sorry, but what is "brg"?

bearing.

 

[littlebookworm]

Re: Alternator Keeps Seizing!

You've indicated tht you're going to deal with two of the problems correctly - using a marine alternator and tightening the belt properly - but you haven't indicated that you'll deal with the third problem - the rat's nest of wires and possible short causing your alternator to try to over-charge and overheat. Boat wiring of that vintage is fairly straight forward and any service manual will give you a general wiring diagram along with proper color coding and wire sizing. Why not take the time in the off-season to do some rewiring. It's not an overly expensive or complex activity and will get all your circuits working correctly and looking good. That will save you a great deal of trouble next season on the water. And please, NEVER use auto parts for fuel or electrical systems when marine parts are required. You're setting yourself up for an explosion when you do. Hy

 

[Allmand]

Re: Alternator Keeps Seizing!

True,
I will be re-doing the wiring in the boat. The rats nest is mainly wires that are no longer connected to anything. They have been bypassed with new wire by past boat owners and the old wire just left un-connected. So it looks like a rats nest. But I have followed each and every wire from the instrument panel to the engine harness and most is good. I just need to find out what wire is there for no reason and pull it so I can have a better view of what I am dealing with. This is my first boat, and I must say, I have done a lot of work to it not knowing much about boats. Getting much of my instruction from here. Learned how to completely go through the outdrive and do repairs, replaced the manifold, and many other parts, learned about wiring, replacing steering, throttle, and shift cables (lower and upper) Gimbal bearing, bellows, etc and just about everything else that deals with operating and repairing a boat. Of course I still have lots to learn, but even though this old boat has been out of the water being worked more often than being in the water enjoying it, I couldnt have asked for a better first boat. By the time I am done with this boat, and move on to a new or newer boat, I will be able to rebuild that thing in the water if needed. So a bright side to everything I suppose. And she's a very unique boat.