1983 Mecruiser (alternator)

[kbrown001]

Hello all,

Last year while enjoying my 1983 Bayliner, 135 hp Mercruiser engine, I noticed that when I ran the motor for a few hours it had trouble starting. The motor starts fine off the loading dock, but when you stop to ski it almost acted like the battery was going dead. The battery was new. After replacing the battery I still experienced the same problem. I stopped by a marine shop and they pointed out it could possible be an alternator problem. They advised I start the boat and then pull the power to the battery, if the engine cuts off then its the alternator.....so we replaced the alternator and the boat still cuts off if you pull the power to the battery. Is this a true test? I performed the test in the yard, hooked up to water, after the engine had been idling for around 5 min. The voltage on the dash does not change when you start the motor and always rest at around 12.

Any help troubleshooting this problem would be appreciated.

Thanks

 

[Bondo]

Re: 1983 Mecruiser (alternator)

Is this a true test?

Nope,... It Frys things...

The voltage on the dash does not change when you start the motor and always rest at around 12.

Ayuh,... That's a Better test, saying the charging system isn't charging...
A Multimeter is even Better....

The factory Manuals are available for download up in the Adults Only section at the Top of this forum...

Welcome Aboard...

 

[Don S]

Re: 1983 Mecruiser (alternator)

They advised I start the boat and then pull the power to the battery, if the engine cuts off then its the alternator.....

Avoid those idiots like the plague. That is the best way possible to blow the diodes in the alternator.

Look in the adults only sticky (second post in this forum) and download the OEM service manual and start reading. Again, do not do that test that shop told you. That's what keeps taking out your new alternators........ Geezzzzz

Who knows, you may have nothing more than a bad volt meter.

 

[kbrown001]

Re: 1983 Mecruiser (alternator)

Thanks for the replies, is that service manual #3?


If its not the alternator, what are other possible problems?


Thanks for the help.

 

[Bt Doctur]

Re: 1983 Mecruiser (alternator)

follow the heavy Orange wire back from the Alt. Does it go directly there or thru a square plastic looking block first.

 

[kbrown001]

Re: 1983 Mecruiser (alternator)

I have attached 2 pictures. The orange wire goes from the alternator through a wiring harness to a box that sits on top of the starter (bendix?).

Thanks for the help.

 

[Bt Doctur]

Re: 1983 Mecruiser (alternator)

This square block is a 90A fuse assembly,can be testeed by bypassing it .voltage gauge should read normal when bypassed.

 

[jack gardner]

Re: 1983 Mecruiser (alternator)

cmpletly avoid the disconnect batt running test .u can create a voltage spike and ruim all ur electronics as well as the alt

 

[kbrown001]

Re: 1983 Mecruiser (alternator)

Sorry for the delay....how do you bypass it, connect the orange wire going into the fuse block to the red wire coming out the other side? At that point where do I check the voltage (i'm a rookie at this)? What are the parts that could possible be causing this problem? To me the battery (which is good), the alternator (which is new), and possible this fuse box...is there anything else? If not could I just replace the fuse box?

Thanks for all the help!

 

[Bt Doctur]

Re: 1983 Mecruiser (alternator)

Once bypassed , start the motor. The Volt gauge should be 13.6-14.6