Alternator Replacement

[andythefiddler]

Hi All,

I'm hoping you will all tell me I've got this one right. I'm not an engineer or a mechanic, pure amateur with years of experience (both good and bad) at sea I only want the good so I talk to you good folk.

My alternator gave up last year, yes really, finished the year off at 12.9V and only just able to lift the Anchor, I'm hoping the batteries (less than 1 year old) did not take any damage.

I have purchased a new one, Yanmar 80 Amp this time, 60 amp is standard.

I took the old one off and the back connections don't match exactly.

I am making some assumptions here and I'd like anyone to comment on, have I got it right.

The plug in terminal connector connects as on the old one.
The bullet connector the same.
The red (marked B+) goes to the batt connection
Black (lighter gauge cable with insulator over) goes to the N
The old unit did not have a specific earth, I am assuming I can run a fairly hefty earth to an earthing point on the Engine.

There is no connection between N and the point adjacent to it - as on the old one, I suspect there shouldn't be?

Photo's enclosed, do we think I've got this right.

Thanks

Andy

 

[superheat6k]

Is the new simply a larger output of the original ? If so I would expect similar connections.

You do not state what engine you have, but an extra 20 amps does not come free and will take up to an extra ~ 1/2 HP from the engine.

 

[Daydream believer]

Is the new simply a larger output of the original ? If so I would expect similar connections.

You do not state what engine you have, but an extra 20 amps does not come free and will take up to an extra ~ 1/2 HP from the engine.

Well it will not do anything, if he cannot connect it up properly
Just out of interest--I would have thought that the additional power consumption only happens when it is charging at the higher amperage , which it does not do all the time. Am I right about that?

 

[penberth3]

Well it will not do anything, if he cannot connect it up properly
Just out of interest--I would have thought that the additional power consumption only happens when it is charging at the higher amperage , which it does not do all the time. Am I right about that?

Yes, you're right. Engine power in will be proportional to the electrical power out.

 

[William_H]

I would have suggested repair the old alternator. If you look at first picture of old alternator at about 8 o'clock there appears to be a plate with a bolt at each end. One being also a terminal. Take this off should expose brushes and the slip rings of the rotor. Herein lies most of the problems of alternator failure. That is apart from bad wiring. Sorry not what you want to hear after buying replacement. The additional 20 amps of capability will not necessarily result in more charge current. That might depend on willingness of batteries to take additional current.
Does your old alternator have built in regulator? (perhaps under that plate) Does the new one have a built in or remote regulator? ol'will

 

[LadyInBed]

Is this thread of any help?
Hitachi Alternator swop
and

 

[andythefiddler]

Hi all, thanks for the input.

For reference the engine is a 3 cyl yanmar 20 HP.

I think I have it sussed now.

Trouble is it has to be connected before I fit the alternator, like many boats the engine bay is very tight.

Loss of half HP, hmm….

When I look at all the other variables that can bother the engine output, I’ll take that.

My current prop is different pitch to the original, making slow speed an issue so swings and roundabouts.

Anyway, thanks again for the input.

Andy

 

[andythefiddler]

Is this thread of any help?
Hitachi Alternator swop

I would have suggested repair the old alternator. If you look at first picture of old alternator at about 8 o'clock there appears to be a plate with a bolt at each end. One being also a terminal. Take this off should expose brushes and the slip rings of the rotor. Herein lies most of the problems of alternator failure. That is apart from bad wiring. Sorry not what you want to hear after buying replacement. The additional 20 amps of capability will not necessarily result in more charge current. That might depend on willingness of batteries to take additional current.
Does your old alternator have built in regulator? (perhaps under that plate) Does the new one have a built in or remote regulator? ol'will

New one is Yanmar with - I think - built in regulator.
and

Very similar yes.