Mercruiser Alternator

[massgc]

Dire need of help here. I had a raw water pump go on me last year and evidently over the winter it froze the alternater because of all the saltwater it took in.

I ordered one replacement alternater (two wire / 863077-1) from DB through Amazon and they sent me two, no problem I will send one back if they pay for shipping.

I have installed both and the best I can do is 11.7 volts. It has to be very hard to hook it up wrong and I hate to think both are bad. If I disconnect the ground I still get 11.7 volts with a digital meter connect to power and ground terminal on the alternator if that helps.

If anybody has any thoughts I would really appreciate it.

Thanks in advance
Jack

[Mr. Sandman]

I've installed a lot of marine alternators, and various current and voltage measurement devices. I am assuming this is on a merc inboard or I/O and not an OB.

You might have done all this but you you really need to check your batteries and connections, that they are clean and solid. (and properly wired with the proper gauge wire and that the wiring is in good shape)

Re- check all grounds.

What is the voltage on the battery itself as measured at the battery posts?

What is the the voltage at the alt, engine off?


What is the the voltage at the alt, engine on?

This sounds like a dumb question but are you sure it is turning in the right direction? Double check all the instructions and make sure you have all the connections and any switches or rear-wiring positioned correctly.

Does this unit have an internal or external regulator? Make sure it is set for the appropriate device.

Let us know how you make out. It is highly unlikely that both units are bad. They are tested before they leave the factory so they probably work fine.

[nightfighter]

Check the coil.... Had a 28' Pursuit with twin Merc IOs. Had to carry spare coils all the time. Those Mercs would burn them out. I'll look to see if I still have one in the shop, even though that boat has been gone for ten years.

[thefishingfreak]

you have to goose the gas a little to excite the alternator first.
Some will self excite. Some just wont.
I have twins. one will-- one will not.
I have to goose it a little to get it going then it's fine

[Mr. Sandman]

That is true. most units have a "threshold rpm" that have to get to before they "turn on", it should kick on before 1000 rpm but you may have to wake it up.

[massgc]

Thanks for all the responses. It's a newer Mercruiser 350 engine (2007)

I'm splashing later this week and see if it wakes up. The batteries are brand new and completley charged. If I remember right I never got much of a charge when trolling but it jumped right up when accelerating but I don't want to run it that high unless it's in the water. It's not Mercruiser original part but it's hard to believe both new alternators are no good.

Thanks again
Jack

[thefishingfreak]

Even a quick snap of the throttle should be enough to excite it and start the charging above 12v
You can do that on the trailer. just givr the throttle a good rev and see if it starts charging. Once excited it will still charge at a lower rpm just might need a kick in the pants to get going
Posted from my iPhone/Mobile device

[massgc]

Thanks, will give it a shot and report back.

Jack

[likwid]

what freak said.

Also did you order the right alternators?
There's parts manuals all over the internet for our engines.

[massgc]

Right part. Number is right on the existing alternator.

[nightfighter]

Originally Posted by massgc

Right part. Number is right on the existing alternator.

Not to be a wiseazz, but that does not always make it the right one.... As Ronald Reagan said; Trust, but verify....

[thefishingfreak]

Also The 2 small wires that come off the back are usually power out to the warning lamp and power in to the voltage regulator. It needs power to excite it. You may have a broken wire leading into the alternator. So it's not exciting itself. Make sure that small wire has key on power also.
Some Hot rods and boats use 1 wire self exciting alternators the 2 small wires are missing
Posted from my iPhone/Mobile device

[massgc]

Because I am anal, I took a photo before I took off the Mercruiser original part. There was only two wires. One red/orange wire at top that I assume was power and one black ground wire.

We'll see what happens.

Thanks again for the help.

Jack

[massgc]

Splashed it today and after I ran up the RPMS it started charging fine. Thanks everyone for the help.

Jack