Yep, that coil and bracket on the side are the main bell. Here's a photo of mine on Sea Ray, the 2 player version of Mariner:

Bell.JPG

Ditto for the Match unit, where yours also seems to be missing the bell:
Match.JPG

Here are the 3 Jones plugs on mine. All 3 are a different size, so yours seems unique in that respect, maybe related to the 4 player version:
Jones.JPG

When you turn power on, hit the left flipper button. Your GI lights should come on. A lot of EMs don't just light up by default.

And as noted, those pins are for setting the award values. There should be a card in the head that tells you what each color is and what each of the available holes is.

When you press the start button, assuming you have some credits in the window, the first thing that should happen is the score reels resetting to zero. See if that happens and report back. If there are no credits, you can try adding some from the coin door, or just cycle the credit unit by hand a couple times.

If you look at the schematic, available on IPDB if you don't have one, find the Ball Count Unit Step Up Solenoid. Follow its traces and you'll see it goes through a number of components: Extra Ball Relay, Ball Index relay, Tilt Relay, Outhole Relay, Coin Unit disc, Player Up Unit disc, Ball Count unit disc and a couple score motor switches. Start looking at those. I'd start with the relays and discs and leave the Score Motor for last.

Each relay has two positions, unlatched and latched. Check the switches in each position. Some will be obviously closed, some obviously open and others will make/break. Watch how they move when you gently push the relay plate in against the coil. That will tell you if any are out of whack. Adjust as necessary and clean lightly. You can use a flexstone if you have one or even a business card moistened with alcohol. You'll probably see some oxidation come off. Don't over-file or go too hard. Once those are done, try running some 600 grit or finer sandpaper over the disc contacts. You'll have to take the disc off to do a proper job, but again, I'd try with it on first. Use the business card trick under the fingers of the spider between those contacts. Wipe the disc rivets down with some light Teflon lube. That will help it turn more easily. Cycle the units by hand to make sure they move freely.

Now try again and see if you get any further.

From your photos, it looks like you are missing the main bell and the coil plunger for it. The rest is there although that coil also looks a little toasty.

For the match bell, I can see the striker there so I think all you need is the bell and maybe some attaching hardware.

Check the 10 point relay. Activate the latch plate gently by hand and see if all the switches are making or breaking as they should. Also, check the End of Stroke switch on the 10 point score reel. Press the plunger in by hand and make sure the switch is changing state. Make sure there are no broken/missing wires anywhere on the relay and reel also. I'm venturing a guess that it's the reel EOS switch not de-energizing the relay.

The Bally fuse holder clips are notoriously crappy. You would do well to change them all, as even if they are not broken they are often high-resistance.

The 10 point circuit gets a lot of use in Sea Ray/Mariner. It may have just been that coil's time to go.