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Old 29-10-2013, 16:14   #1
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How hard to install new alternator?

Our 1961 graymarine has the original 10 amp generator. I would love to put a 25 amp on...any ideas what might match up or what it would take to install a new alternator?

Our old generator has a spindle inline which runs the water pump...

Can i get old generator rewired for more amps?

Is that more than $100?

Curious what options you think i have.

Thanks

Christian
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Old 29-10-2013, 16:16   #2
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Is there room to add another alternator leaving the original in place?
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Old 29-10-2013, 17:07   #3
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It is true that 10 A doesn't sound like much, but what type and size batteries do you have, or would you like to have?
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Old 29-10-2013, 19:04   #4
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Re: How hard to install new alternator?

I'll post a picture of the area soon
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Old 29-10-2013, 20:58   #5
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Re: How hard to install new alternator?

alternator shops should be able to rewind it bigger.
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Old 30-10-2013, 15:59   #6
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This is a generator right? I wouldn't bother trying to increase the capacity of a generator but would rather install a 100 amp or so alt if possible. give you redundancy as well.
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Old 30-10-2013, 16:03   #7
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I don't know how to edit or I would, but a "one wire" GM alternator exist that is dead easy to install, it's just one wire that hooks to the batteries and your done, the regulator, didoes etc are internal to the Alternator, I would use the Gen to charge the starting battery, but use the alt to charge the boats battery bank
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Old 30-10-2013, 16:15   #8
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If you rewire, replace or add on there are two ancillary issues to consider.

First, the engine is 52 years old. It has spun the 10 amp device for 52 years, and now you are going to add some significant load. I know from experience that you will be able to hear the difference in the engine with the load.

Second, I am assuming that this is a one belt system. I know from experience that if you (or in my case the PO) add a 100 amp the belts will begin to wear much faster.



If you do go forward, you can mitigate these issues with a Balmar smart regulator. This regulator allows you to temporarily "de-rate" by 50%. So the 100 amp behemoth only generates 50 amps when you are day sailing or will have dockside power, or will have a long engine run at the end of the day. But if you need all 100 amps, just disconnect one jumper (or you can wire it to a switch) and viola! 100% capacity.

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Old 30-10-2013, 16:41   #9
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Sounds good, yes there is no such thing as free power, it will take more than 100 amps of power from the engine to generate 100 amps of power that's a fact, nothing is 100% efficient, but unless your batteries are pretty much dead, your alternator won't be making 100 amps will it? Assuming the batteries are decently charged to begin with, then your only making about the amount of current that is being used which if he has been getting by with a 10 amp gen, isn't much at all.
I'm going to guess that to make 100 amps at 14V will pull about 4 or 5 hp from the engine? Just a guess, but it will be a significant draw that's for sure.
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Old 30-10-2013, 17:02   #10
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Re: How hard to install new alternator?

Quote:
Originally Posted by a64pilot View Post
Sounds good, yes there is no such thing as free power, it will take more than 100 amps of power from the engine to generate 100 amps of power that's a fact, nothing is 100% efficient, but unless your batteries are pretty much dead, your alternator won't be making 100 amps will it? Assuming the batteries are decently charged to begin with, then your only making about the amount of current that is being used which if he has been getting by with a 10 amp gen, isn't much at all.
I'm going to guess that to make 100 amps at 14V will pull about 4 or 5 hp from the engine? Just a guess, but it will be a significant draw that's for sure.
In a perfect world 1 watt = 0.00134102209 hp

In that same world 1400w = 1.87743094 hp

YMMV
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Old 30-10-2013, 17:26   #11
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I had looked it up myself and seen that at 100% efficiency that 1400 watts equaled about 1.8 HP, but I have no idea about an alternators efficiency and remember reading somewhere that a belt run at average speed ate up over 1 hp just going over an idler pulley, if true I think it would pull probably at least 4 hp or so to make 100 amps at 14V, plus of course it's just good practice to be conservative
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Old 30-10-2013, 17:29   #12
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Re: How hard to install new alternator?

Is this a gas or diesel graymarine? Does it have the generator bolted right onto the belt housing using a flange and a tie rod connected to that going to the water pump?

If so, you don't really have many options for adding an alternator. The generator will need to stay in place. You would need someway to mount an alternator, as well as someway to access the crankshaft for a pulley and belt.

I have seen exactly one graymarine gasoline engine in my life, and that was decades ago, so I really don't remember much. But I THINK I remember that the generator is run from a belt that is machined onto the flywheel, and doesn't have any place to bolt a power takeoff pulley for any extra gear. Let alone that fact that I remember it being all covered with a heavy metal casting.

This is all by memory, but even if I'm really off, you will need to find some way to mount an alternator with one of the standard footings and find some way to get it turning when the engine runs. That also brings up pulley ratios depending on what max rpm the engine operates at.

All in all, you may have quite a challenge there.

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Old 30-10-2013, 18:14   #13
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Re: How hard to install new alternator?

Based on the above comments (I don't know Gray Marine) this may be a perfect case for solar.
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Old 04-11-2013, 09:51   #14
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It is a gas gray marine. The generator is mounted inside of a quarter inch steel shroud. No room to add on. I will have to rewind if at all. Any idea on a rewind price and how selective I need to be on the shop? Can any shop that offers the service do a good job?
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Old 04-11-2013, 10:08   #15
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Re: How hard to install new alternator?

You may have a hard time finding a shop that knows anything about generators at all. But, Look up electric motor rewinding.... your gen is just a motor run backwards really. Possible to mount a Alternator where the gen mounts? I dont know why others made the leap to 100 amps... a one wire 35 amp alternator would triple your charging rate and have no problem with one belt.
Our old generator has a spindle inline which runs the water pump...
Not sure what this means... you mean the WP runs directly off the Gen shaft rather than another pulley?
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