Mercruiser 5.7l MCM which replacement parts to buy?

leeirvin

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May 18, 2020
Messages
9
Hi all, me again. Thank you for helping in advance. And thanks for the help with the ignition.

For reference: Mercruiser Serial 0L692104 5.7l MCM Thunderbolt V.

I'm now replacing the starter and alternator. The starter died on us at the lake today. I took it down to Advance Auto and they put it on a tester and said she failed their testing machine.

Question is, which parts do I replace with? Both the starter and alternator are Arco, so obviously not original. I can put back in, or would I be better off going with Sierra or Quicksilver (which I assume is Mercury OEM?)

Then - these sites that you put your serial number in and find your part.... they list one Mercury OEM part but it says it has an offset bolt pattern. Then they show a Sierra part and the Arco I pulled out. The one I pulled out was the Arco 30470. According to this website that has a staggard bolt pattern.

http://www.marineengine.com/parts/mercury_marine_parts/sn/0L692104/4311025N1/2697_40

(and is there a good site from which to order?)

So can I just buy the Mercruiser OEM part? Is staggered the same as the offset?

And, this may be a matter of opinion, but is OEM better than Sierra and sierra better than Arco? Or are they all about the same?

I am also adding a second battery, starter, and house. Is there any benefit to getting a higher amp alternator? And is there such a thing for this motor? My searches have not come up with any good information. I love running the boat around the lake and through the river channel, but the boys like to stop and fish or swim.

I love wrenching as much as I love cars and boats, but I am beginning to yearn for a little more boating time.
 

alldodge

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Mar 8, 2009
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43,319
Offset and staggered are the same

Suggest looking for "Marine GM PMGR Starter" and several will come up. Get a major brand and I would stay clear of Sierra and Arco, but just my opinion. The PMGR is smaller but has more torque so much easier to install, I have one on my 502

Thanks for the serial number
Your motor came with either a Mando or Delco alternator. If you look at the link and then see which one you have, I would replace with the same. Can use Merc but could also just search for "marine" then use Delco or Mando and see what shows up

https://www.mercruiserparts.com/5-0l-2-bbl-gm-305-v-8-1998-2001-0l0

Your sure that both ALT and starter have gone out?
 

leeirvin

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Joined
May 18, 2020
Messages
9
Starter yes. She clunked real loud and bad and wouldn't turn the engine over. I was worried about flywheel teeth. I was relieved when the Auto Parts place said it was failing (drawing high amps and not spinning fast enough)

The alternator is technically in spec @13.8 with the tester I put on it. I think that is the lower end of spec right? The dash voltmeter has not come above 12.5 with the engine at 3800 rpm. (I've never put a lot of faith in the dash instruments) I'd breathe a bit easier if she was North of 14. She was also giving me a hard time when I was trying to set the timing. I don't think it was getting enough juice and the timing light would fail to flash. Heck, could be faulty timing light. It's the first I've touched in 30 years.

My first IO and first Mercury 350. So I don't know my way around aftermarket parts. I just want to get reasonably dependable parts.
 

leeirvin

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Joined
May 18, 2020
Messages
9
Ha, I did that search. There's a ton. I read a post where a guy bought a $38 starter and everyone asked him what he expected for $38. If Arco and Sierra are not necessarily desirable, then I guess mercury?
 
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