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merc 140 alternator problem???

H

hrhvt

New member
Hi,
I'm a fairly new boat owner with a 1984 sea ray, it has a mercruiser 140. The other day we were out, doing fine, all of a sudden the engine died.
Restarted, but battery seemed to be struggling to turn it over. Put a portable jumper on it, and it started, but could not give it too much gas or it would die again, so we limped back to the dock.
Also noticed when i went to put the engine up or down at the dock, it died, seems anything with too much electrical caused it to stall out.
I am thinking alternator or loose (stretched) belt and will change the belt this weekend, just in case. I took the alternator off and am hoping to go to the auto store to have them check it.

Am I on the right track or could it be something else.

Thanks for any help

Kevin
 
Marine batteries are seldom taken care of adequately. When left in a SOD for any length of time, it takes it's tole on them.

You may want to pull the battery and take it in to a Battery/Starter/Alternator shop, and have it load tested.
If questionable.... replace it!


.
 
RicardoMarine said:
Marine batteries are seldom taken care of adequately. When left in a SOD for any length of time, it takes it's tole on them.

You may want to pull the battery and take it in to a Battery/Starter/Alternator shop, and have it load tested.
If questionable.... replace it!


.
Click to expand...

I appreciate the reply.
The battery is brand new last summer and I pulled it inside the house for the winter. I will take it to get it tested, but I wouldn't think it would be the battery already. I will have it tested though. Thanks
 
So, last night I took the battery, and the alternator to the auto parts store. They tested the battery and said it was fine> They were unable to test the alt because they said it was a marine alt and did not hook up the same way or some reason like that. Anyway, unable to test, but they suspected that was the problem so I suppose I will just get a new one and see what happens. Will also replace the belt.
 
This may be a dumb question, but did you tighten the belt first, and give that a shot? If you have a volt meter you should be able to check the alternator output while installed on the engine...
 
Fastatv said:
This may be a dumb question, but did you tighten the belt first, and give that a shot? If you have a volt meter you should be able to check the alternator output while installed on the engine...
Click to expand...

Not a dumb question at all. There was some play in the belt, not sure how much is too much, but it didn't seem too, too loose. The belt was, unfortunately, all the way over as far as it could go, and so could not get any more tension on it.
The belt looked good though, and not worn or torn. I was going to buy a new belt 1 inch shorter, so that it has a little more tension on it.
Perhaps I should do that before I replace the alternator, that way I can test them out one at a time, and see if the belt does the trick.

Thanks
 
I did try to watch it, but it was kind of jumping around, and not that accurate i think. sort of bouncing. I think I may have a voltmeter at home. If i knew exactly where to hold it as i tested it I could try that . Hate to buy an alt if it is just the belt. I guess change the belt first and then see what happens.
Should be a nice weekend so like to get this done today, or else have to order an alt and wait till next weekend. I live in vermont so good weekends are to be taken advantage of.
 
If you have a very loose belt, at low motor speeds (under 1500 rpm) the alt may not be outputting to recharge battery.
Thus the battery would be running the ignition and accessories thus draining the battery. Once battery voltage gets too low the ignition may stop functioning.


I would recharge the battery
Tighten or replace the belt

Run on hose or in water and check volt meter in the dash or better is to put a hand held volt meter across the battery and measure what voltage is there when engine is running at 2000 rpms.........as BT Doc said should be at least 13.6 VDC at 2000 rpms. Boat can be in gear running (when in water) or just reving it up to 2000 rpms in neutral. does not matter.
 
hooked right to the battery, read the voltage with the motor off eg: 12.8v .then start the motor. reading should be higher 14.6v
 
Well, I was going to reply again but for sure Bt Doc and kghost covered it here. I hope the charged battery and new belt does the job for you. Good luck and let us know what you find.
 
Fastatv said:
Well, I was going to reply again but for sure Bt Doc and kghost covered it here. I hope the charged battery and new belt does the job for you. Good luck and let us know what you find.
Click to expand...

Ok, Wasn't sure if I could check the voltage right from the battery or if the voltmeter had to be on the alt somewhere. So, I should be able to replace belt today and then check it all out. I'll let you know what happens.
Thanks for the help

btw, When I had it running on a hose yesterday, it ran fine, but whenever I put anything electrical on it ie: bilge pump, wiper, whatever, I saw the vlotmeter on the dash drop suddenly and jump.
 
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