A very dumb question

[walker]

I have only really done charters before and had a nice friendly engineer to call on when things have gone wrong. Next week I am going out to our own boat (share) for the first time and the first thing I have to do is fit, or have fitted, a new alternator which I will take out with me. It looks pretty simple out of the box and my first inclination is always to have a go - I am assuming if I look at how the old one is fitted/connected I should be able just to replicate that with the new one. But I would be very grateful if any forumite could warn me if there is more to it than that, potential pitfalls, or whether I should get the yard to do it and watch for future reference.

Also the new unit has a small dent on the flat round plate that carries some fan-like blades - probably onlya 3-4mm deflection. Doesn't look like it should be a problem and I am reluctant to return because it has taken us quite a time to get this warranty replacement one. It is between 'blades' so doesn't affect their angle nor does it affect the turning of the fan if that is what it is. Should it be OK?

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[Althorne]

I can see not problem with the dent providing it does not inhibit the flow of the fan or air flow to cool the alternator. If it runs smoothly then the bearing is undamaged. I would advise the supplier prior to fitting in case rapid movement attached to the engine could change things.
With regard to fitting you are correct in saying fitting is the reverse of removal mechanically providing everything is near indentical but I would make a diagram of any electrical fittings before touching it to prevent any nagging doubts YOU have done something wrong should it not work afterwards and treble check connections before starting engine. Just make sure you do not run it with the motor without it all being fully wired up as this can distroy it if not connected.

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[walker]

Thanks for that Althorne - I'll give it a go having as you suggest made careful diagrams.

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[abdiel]

Mark, there is no such thing as a dumb question on reader to reader, we all have to learn and we arent all experts. Lets have no more of this nonsense and good luck with the alternator.

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[Sea Devil]

snapshots with the digital camera are great for reference - fan belt tightness is a possible downfall...

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[Talbot]

There are no really dumb questions (assuming questioner is not trying to wind up people), but there can be a lot of dumb answers - especially when you think someone is trying to wind you up but wasnt. You can bet that any question you ask will cause a sigh of relief elsewhere cause they wanted to know the answer as well! /forums/images/icons/smile.gif

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[jerryat]

Hi Mark,

Definitely not a dumb question! There must be more cock-ups made when fitting alternators than any other bolt on part. I agree with Althorne, make a good clear diagram and, I would suggest - use a relevant colour for the wires rather than just rely on a pencil or pen lines, it's MUCH clearer. Then file your quality diagram for future use!

I still do it this way even after owning boats for over forty years, because it is amazing how many times the fitting of the new/refurbished part is delayed for a day or two when something else crops up. I find it easy to forget what I was 'sure to remember' when this happens and a clear coloured diagram becomes an absolute Godsend.

Best of luck and I hope it's works brilliantly for you.

Cheers

Jerry

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[stokes]

"sure to remember" as a young rep. a large store in York was called on for the second time ."could i see Mr Sword" (who could forget that name) i asked, blank looks from the three girl assistants.......We have a Mr Dagger who is a buyer offers one..............................

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[misterg]

Things to check before you start...

Disconnect or isolate battery (just in case)

1) Hold the "new" alongside the "old" and double check that the mounting lugs line up on each at the same time as the drive pulleys line up.

2) Try your drive belt on the new pulley - does it sit the same way in the new pulley as the old one.

3) Make sure the electrical connectors from your engine are the same type as the new alternator - do they look the same? Can you plug them into the new alternator before it's fitted, just to check?

If alternator is a true replacement, then all these should be formalilies.

Make sure you reconnect battery before testing.

As regards 'dent' - is the metal bent, or missing? Make sure the fan is running true before fitting the alternator. If it is metal missing, it may have been done to balance the fan.

No such things as dumb questions.

Andy

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[walker]

Thank you all for the very helpful answers - they have given me the confidence to have a go AND I don't feel quite so dumb anymore! Will certainly take the excellent advice re diagrams and digital photos. I must say that I have tended in the past not to bother learning about matters mechanical, mainly because the whole time I have had a car I have been living in London and the car has been parked on the street (and often not our street), but I am really looking forward to learning how to do stuff myself on the boat. Quite fancied the idea of getting hold of a wrecked diesel engine and taking it apart to understand how it works but SWMBO vetoed that given that the only place I could have done it was on the dining room table. Some women are just so unreasonable! Thanks again.

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[Talbot]

I rememmber my mother was not overly impressed when she came home to find me (as a spotty teen) with my Lambretta engine in bits on the dining room table (I had used newspaper so couldnt really see what the problem was!)

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[LadyInBed]

<A target="_blank" HREF=http://www.vtr.org/maintain/alternator-overview.html> This </A> may or may not be of any help

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[waverider]

All sound advice here....another good addition is to take a tube of copper slip to smear liberally on the bolt threads on assembly to prevent the threads from siezing if the alternator has to be changed again in the future!

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[nordic]

With regard to advice re "copperslip". Do not apply liberally! A little is enough as any grease in excess attracts dirt which acts as grinding paste next time you undo the nut/bolt. A bead down the length of the bolt threads is all that is required. Excess grease in a blind threaded situation can prevent full tightening of the bolt and can crack a casting through hydraulic pressure if really done to excess!

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[waverider]

Sorry Nordic...but because of the viscosity of copper slip compared to grease I cannot imagine anyone cracking castings....unless of course they filled up the bolt or stud hole with the stuff.........last of all if you even dipped the thread of a bolt in the stuff and screwed it into a thread the excess would not enter the thread, it would just gather on the surface as the bolt screwed in!

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[pampas]

Have sent you a PM

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[copterdoctor]

I changed my alternator last year. I'm supposed to be an "expert" in such things and get into all kinds of trouble. The upshot was that my friendly Bukh dealer forgot to mention that not only did I have to follow the wiring diagram supplied I also needed to change some of the internal wiring.
It's only a dumb question if you already know the answer.

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[andy_wilson]

Just a further word on the 'dent'.

Alternators are always geared up to rotate faster than the engine RPM.

If the dent causes a rotational imbalance this could affect bearing life.

Can you not use judicious use of force to straighten it out?

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[walker]

Thanks. In view of your and Althorne's advice I have spoken with the supplier and let them know the situation - they reckon it should be fine. I did think about trying to straighten it out but figured that if I tried and e.g. damaged the bearings in doing so it would then be 'my fault'.

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