? wire size for bosch starter

[broadsword]

Hello Everyone,
I’m new to tinkering with boats and have jumped in with both feet so to speak. Project 1 is a recently purchased 24’ glass commercial fishing boat. project 2 is a boat and trailer I picked up for free recently, It is an old glass AMF Crusader, approx 17’ with a pretty good looking merc cruiser I/O. Haven’t had either started yet. I haven’t tried to start the AMF, still tearing out the interior to prep it for a hard-top conversion. Yes, I’m pretty enthusiastic. We will see how long that and the bank account last.
My first of most likely many questions is; what wire size should I use from the battery to the starter? The starter is a Bosch 0-001-362-304, 12v, 3kw. It is starting an old BMW D-150, turbocharged, 6cyl, diesel. I was going to purchase tinned marine grade wire with custom crimps for length witch should be about 3’ from the battery to the starter and about 5’ from the battery to ground. My idea was to go big and get 2/00 but If this is a bad idea I would like to know.
I have searched for specs on this starter and haven’t found much info. I would like to know what size battery I need? I bought 2 of the marine batteries at Costco and the starter would crank but real slow. So I cleaned the existing battery wires both + and -. The + wire is large and appeared to be ok ( didn’t cut the insulation to check for corrosion.) The - wire is smaller and didn’t look so good. I cleaned as well as I could with a wire brush, put it all back together with the new battery and nothing changed. I pulled the starter and had it tested under a load and it checked out ok. I suspect the negative wire and the cranking amps of the battery. The battery says 750MCA ? and 150 amp hours ?
I’m thinking about buying a new starter as this one has been err ummm ohhh yea the term they used was rebuilt at least twice by the same auto shop that charged me almost $30 each for glow plugs. My experience with rebuilt and aftermarket parts has not been good. Where can I find new Bosch parts for a reasonable rate? I also would like to try to get my hands on a shop manual for the motor, but that will be in another post.
I have found some good reference to some books on this site and will be researching them.
I thank you all for your wisdom and help. From what little I have read it is quite apparent that the people on this site are generous with both and it is greatly appreciated. I also appreciate your patience with my ignorance and lack of experience.
Thanks,
Michael

[broadsword]

Hello everyone,
I have purchased a few books by Payne. I’m in the process of educating myself, in the hopes of rewiring my boat. There were many who viewed my post and when I didn’t get a response I started to think why? After rereading some posts and the books I have come to the understanding that I need to learn about the whole system to work on part of it. I’m sure I will have many questions but hopefully they will be more educated and specific.
If anyone has suggestions for other must have books, please let me know.
Thank you all for your contributions in making this a wonderful site.
Michael

[RHough]

Originally Posted by broadsword

After rereading some posts and the books I have come to the understanding that I need to learn about the whole system to work on part of it. I’m sure I will have many questions but hopefully they will be more educated and specific.

I predict that you will get good information in response to future questions. "Your Boat's Electrical System" by Miller and Maloney ISBN 0-688-08132 is a good reference also.

[Corpus Skipper]

2/00 wire will be fine. Bigger is always better, especially for turning over diesels.

[broadsword]

OK! I’ve opted for 1/0 wire. Question now is battery/batteries? The starter is a 2.7KW. 2,700watts divided by 12v=225amps. Is this correct? Will I need batteries that will produce 225 amps? This seems awful high to me. The motor is a BMW D150W and I have not been able to find starter battery recommendations. I have started to study the books I have and I’m a little overwhelmed. There is so much information and I really don’t know where to start.
Thanks

[Corpus Skipper]

The starter is a 2.7KW. 2,700watts divided by 12v=225amps. Is this correct?

Yup! I would probably go for 600 cold cranking amps minimum, as before, more is better. Definitely a good idea to have 2 starting batteries and a switch as well, especially if you're going to be heading offshore.

[broadsword]

Thanks Craig & RHough,
Wow! 600 CC amps! Mayhap I should have gone with 2/0? I have purchased 1/0 wire and lugs but have not installed it yet. The table in my book only goes to 2/0 rated @ 390A. Will I need larger cable than that? Will 1/0 be sufficient? There will be no other load on the starting battery and cable, do I need to rate the cable for the load of the starter or the potential of the battery? Can you recommend a good battery for the buck? I would rather pay a little more if it’s not just for a name. A quick search has produced Optima and the price seems reasonable. Is this a good battery? Is there a “bar none” best battery? I remember reading a warning in Payne’s book about overpriced “marine” batteries. I will do some research on batteries but I really value the experience you guys have.
Go figure! I’ve never owned a boat before and haven’t fished commercially for 20 years and as soon as I commit and get a boat and all the permits, licensing and miscellaneous stuff ($ near 20 thousand) the powers that be announce that their considering closing salmon fishing for the first time in history. News paper said they want to close salmon to all fishing from central CA into OR. Yeah, I have plenty of luck, all bad!
Thanks so much for all your help,
Michael