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Old 28-07-2019, 01:26   #1
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rebuild

Good morning

I am just about to rebuild both my 8V71 motors which were on 32v starters and 1x 32v alternator,

I now wish to change to 24v (can still use 3x 8v battery) but will I have to change 32v starter motors, or will 24v crank them high enough.

Failing this, can the 32v starters be converted to 24v?

32v charger stuffed.

Money is a priority so trying to minimise costs.

Cheers

gbmacca
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Old 28-07-2019, 02:32   #2
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Re: rebuild

My understanding is that if you try to run 32v starter motors on 24V you will quickly burn them out. (The starter motor will not be able to handle the amperage)
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Old 28-07-2019, 03:19   #3
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Re: rebuild

Quote:
Originally Posted by gbmacca View Post
Good morning



I am just about to rebuild both my 8V71 motors which were on 32v starters and 1x 32v alternator,



I now wish to change to 24v (can still use 3x 8v battery) but will I have to change 32v starter motors, or will 24v crank them high enough.



Failing this, can the 32v starters be converted to 24v?



32v charger stuffed.



Money is a priority so trying to minimise costs.



Cheers



gbmacca


Your V8-71 engines will start easily with 24 volt starter motors, in trucks these engines sometimes even used 12 volt starter motors but the bigger issue when converting to 24vdc might be all the other electrical stuff on the engines..... like gauge senders , shutdown solenoid and charge alternators. Is the whole D.C. System aboard running at 32volt? If so you might have a lot more to consider than just 2 starter motors.
Another thing to check before buying new starter motors is whether both engines rotate in the same direction or whether you have a left hand and right hand rotation pair, Detroits can be either.
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Old 28-07-2019, 18:51   #4
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Re: rebuild

Gosh, many thanks, some easy to understand answers, as I feel sometimes these blogs go a little bit 'Nuclear Scientist'!

Firstly - is amperage higher in 24v than 32v? I know little about electrics.

And from another blog, I 'think' only the starter motors and winch were 32v with all the rest, cut offs, senders and the like, being 12v.

I had 4x 6v to make 12v - then 4 x 8v to make 32v on a 110v system which the generator was - which - when we got it to Australia - when plugged into shore power, was 240v.

Very hard to get 32v bits here in Australia now - so reason would like to change to 24v. Boat now has 12v and 240v running through.

CAn I convert starters to 24v or easier to buy new ones?

MAny thanks for your replies.

Cheers

Gbmacca
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Old 28-07-2019, 19:10   #5
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Re: rebuild

Talk to a business that rebuilds large starters about conversion, I doubt it. 24v will draw more amps that the 32v. Amps= volts x watts. You may need heavier cables. There are some 24v DD starters on https://www.ebay.com.au
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Old 28-07-2019, 19:35   #6
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Re: rebuild

Quote:
Originally Posted by gbmacca View Post
Good morning

I am just about to rebuild both my 8V71 motors which were on 32v starters and 1x 32v alternator,

I now wish to change to 24v (can still use 3x 8v battery) but will I have to change 32v starter motors, or will 24v crank them high enough.....


gbmacca
Tough question, the current drawn by the starter motor is inversely proportional to it's speed. It is also directly proportional to the torque developed by the starter motor. This is a feature of a series wound stater motor.

The torque required to start your engine will remain the same but as your voltage is reduced, the speed of the starer motor is reduced which allows for increased current to develop the same torque. This increased current draw makes the starter motor run hotter.

If your engines start easily and quickly, I think you will be fine however if they require a lot of cranking, the starter motor will get hotter sooner.

I would monitor the heat of the starter motor and if it isn't getting too hot, you will be fine.
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Old 28-07-2019, 19:38   #7
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Re: rebuild

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Originally Posted by gbmacca View Post
.........

Failing this, can the 32v starters be converted to 24v?
.............

Money is a priority so trying to minimise costs.

Cheers

gbmacca
AFAIK, they can't be converted cheaply.
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Old 28-07-2019, 19:48   #8
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Re: rebuild

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Originally Posted by skipperpete View Post
...............
Another thing to check before buying new starter motors is whether both engines rotate in the same direction or whether you have a left hand and right hand rotation pair, Detroits can be either.
Yes, worthwhile to check however starter motor directional can be reversed fairly cheaply if needed.
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Old 28-07-2019, 20:05   #9
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Re: rebuild

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Yes, worthwhile to check however starter motor directional can be reversed fairly cheaply if needed.

So the starter drive is different, but how do you change the rotation of the motor? Is it as simple as re-wiring the brushes?
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Old 28-07-2019, 20:44   #10
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Re: rebuild

You could just wire them up 24V and see how they crank and if it will start the engine and since one usually only cranks for a few seconds I doubt that the starters will get hot enough to do any damage.
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Old 29-07-2019, 00:51   #11
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Re: rebuild

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So the starter drive is different, but how do you change the rotation of the motor? Is it as simple as re-wiring the brushes?
Pretty much - you need change the direction of the current though either the armature or the field winding but not both.
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File Type: pdf starter winding.pdf (16.7 KB, 21 views)
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