Mercruiser 888 tripping breaker @ 3200 RPM

[jaxsez]

I am new to this forum and boats themselves, but not to green around mechanical things. I have 1975 Sea Ray with 302 and 888 outdrive.
This past weekend I replaced the alternator in the boat with one that is the same one I think, I am not sure if there were different voltages in that model.
The problem is that at anywhere above 3200 RPM it kills all the power and trips the breaker on the top of the engine. I then reset the breaker, restart it and I am on my way. I am wondering if my new alternator is too high of a voltage, or could there be an voltage regulator that is bad? Also my amprere guage now is pinned all the way to the left but when I was running it in my driveway after I installed the alternator it was above 0
Any help is appreciate. What is that breaker resetting?

 

[Don S]

Re: Mercruiser 888 tripping breaker @ 3200 RPM

First thing I would be doing is putting a volt meter on the battery and seeing what the voltage is at idle, then slowly move up the rpm range. If it hit's 17V, stop. Have the battery load tested and your new alternator checked out.

 

[jaxsez]

Re: Mercruiser 888 tripping breaker @ 3200 RPM

Thanks Don.
I was doing some more research online. It looks like there is a 63amp alternator and a 94 amp one. I think I have the 94amp on and I wonder if that is trying to push more juice through at the higher RPM's. My old alternator did not have any part numbers on it I could find. I wonder if that 100 amp I have is causing the problem. I also could not cross reference the numbers to find out what that engine originally came with.

 

[coastalcruiser]

Re: Mercruiser 888 tripping breaker @ 3200 RPM

Thanks Don.
I was doing some more research online. It looks like there is a 63amp alternator and a 94 amp one. I think I have the 94amp on and I wonder if that is trying to push more juice through at the higher RPM's. My old alternator did not have any part numbers on it I could find. I wonder if that 100 amp I have is causing the problem. I also could not cross reference the numbers to find out what that engine originally came with.

Amperage given by the alternator is always variable, if you have a 100 amp alternator and a full battery it wont give even 1 amp. Voltage is what you need to check. The normal voltage while engine is running is about 14 volts.
Newer boats have voltage meters instead of amp meters
check it with a digital voltmeter, My humminbird depthsounder has one built in

 

[jaxsez]

Re: Mercruiser 888 tripping breaker @ 3200 RPM

Thanks guys. I will grab a voltmeter and test it.
I really appreciate the help.
Chris

 

[jaxsez]

Re: Mercruiser 888 tripping breaker @ 3200 RPM

Ran some tests over the weekend.
Put a voltmeter on the battery and ran the RPM's up to 3200 and the voltage stayed the same about 14.2 to 14.5 volts. When the breaker threw there was no change in voltage on the battery.
Also put leads on the back of the breaker and ran up the RPM's to 3200.
The voltmeter was an AC voltmeter so I am not sure if you have to mulitple it by 12? The amperage reading was running around 1.2amps, but then at 3200 rpm it shot up to 10.x amps before it threw the breaker.
This does not make sense to me. Why would it wait until 3200 to hit it spike rather than anytime if the alternator was causing this. Remember I put a new alternator in the boat, and I think the original one was a 61 amp and the new one I put in is a 94 amp.
Any more ideas? The next this I do is put the old alternator back in it and do the same test, but it is about to rain today so that won't be happening today.

 

[Surfdancer]

Re: Mercruiser 888 tripping breaker @ 3200 RPM

From what I understand, the 888's came stock with a 42 amp alternator. If the battery is not fully charged, a big alternator will push some significant current through the breaker to charge that battery.

What is your battery condition? If it's more than a few seasons old, then it may be soaking up some serious current after starting and warming the engine.

While you're checking, make sure your ground and positive leads are well connected = no loosening, corrosion or excessive moisture buildup. I like to clean them then coat them with grease or Boeshield to prevent moisture intrusion into high current (and other) electrical connections.

Getting back to your question, once the alternator spins up to a certain speed, it finishes charging the stator windings. Then it can really push out the juice.

 

[Don S]

Re: Mercruiser 888 tripping breaker @ 3200 RPM

The alternator does not charge the battery through that breaker. If you don't have an amp meter to checkout the amps going thru the breaker, and since there isn't a way of testing the breaker, Put a new breaker in and see if it works.
Bet it will.

 

[Bondo]

Re: Mercruiser 888 tripping breaker @ 3200 RPM

Also my amprere guage now is pinned all the way to the left but when I was running it in my driveway after I installed the alternator it was above 0

Ayuh,... You wired something Wrong, Somewhere,... That's a Dead Short...

It's not about the amperage rating of the Alt...
A 200amp Alt. will put out Nothing til the systems calls for Power,+ then only what is called for...

 

[Don S]

Re: Mercruiser 888 tripping breaker @ 3200 RPM

Nice catch Bondo

 

[jaxsez]

Re: Mercruiser 888 tripping breaker @ 3200 RPM

All,
Thanks for all the great advice.
As far as the battery it is brand new. No corrosion, etc.
The Amp guage worked at first once I installed the new alternator it was reading above 0. But after the first time the breaker tripped the guage has been pinned to the left along with the oil guage not working.
I think Don might be onto something as far as replacing the breaker.
On that note.... Does anyone know where I might find one for that type of application?
One more quick thought, could the ignition coil be messed up and be a faulty part calling for too much juice?

You all are awesome.

 

[willieboy]

Re: Mercruiser 888 tripping breaker @ 3200 RPM

You have a loose or broken wire somewhere. I have had that happen before with loose terminals as well. Since you just replaced the alt, I would check the wires that you disconnected and make sure they are all good.

 

[coastalcruiser]

Re: Mercruiser 888 tripping breaker @ 3200 RPM

I know how frustrating it is had an 888, if its a short or wired wrong maybe do a start test. Here is a link, By Don S http://forums.iboats.com/showthread.php?t=167035 from the adults only sticky
grab a light and test it. maybe you will come across the problem and please let everyone know what it was.
if you need a breaker check craigslist, lots of parts

 

[jaxsez]

Re: Mercruiser 888 tripping breaker @ 3200 RPM

Closure FYI:
I found out what the issue was. It seems the new alternator I bought was bad, I am thinking the voltage regulator was not regulating properly. I bought another new alternator with a lower amperage rating and it seems to be working correctly.
Correct voltage off the alternator and correcet off the battery, and no tripping the breaker at > 3200 rpms. I am taking for a real test drive this weekend.
Thank you all for your ideas and help.
Chris