Hi Girth,
Welcome to the forum. You are going to become an expert sailor, if you stick with these guys. There is about a thousand years of sailing experience here.
Your new-to-you Mariner is a beauty. She looks to be around the same year as mine, '73. The hull number should be etched into the transom on the starboard side of the rudder. That will have the year and production number coded in it, if you don't already know her age.
Hull ID Help - Mariner Class Association
Step one: (Just as JS said) make sure she will float. Easily said, harder to do. - Inspect the hull for cracks, soft spots, especially around the centerboard trunk. Mine came with a sloppy repair around the forward connection with the boat bottom. The cockpit is self-bailing. That simply means there are scuppers that drain water back into the sea. The Mariner does this through two scuppers located in the outboard forward corners of the cockpit sole. These are connected by half-inch tubing to thru-hulls on either side of the centerboard trunk, about a foot out from center. You can inspect these parts, especially the hoses, from below, just behind the companionway on either side. Mine fell apart in my hand when I pulled on them. If they are old enough to be original, replace them or you will have two half-inch holes in the bottom, letting water pour in. Another place for water ingress is the CB (centerboard) pin. This should be a 3/4" brass bolt, low, through the forward sides of the CB trunk. There might be heavy rubber washers both between bolthead and trunk, and between nut on the other side and the trunk. There is usually a pair of rubber washers also inside the trunk between the cast iron CB and the trunk. Inspect. If everything looks water tight, you have options for the next part.
Inspecting the centerboard: The easiest way to see if the centerboard is not swollen with corrosion and stuck in the trunk is to launch the boat and try and drop the cb into the down position, but to actually look at it, you will also need to go swimming. Your other option is to pick the boat up off the trailer so you can drop the board on land. I won't go into ways to do that unless you need that advice specifically.
Raising the mast is not difficult on a Mariner. I did it easily by myself the day I brought mine home. But, I caution you to be sure she is secure in her ways. Hitch the trailer to a vehicle, keep the trailer straps on her. Don't walk around on deck if she could canter backwards, either lifting the tongue of the trailer or rocking her stern down to the ground and lifting her bow in the air.
Straighten her stays and clear any loops or possible kinks in the cables. Lay her turnbuckles in line with the aft folded mast, and make sure the forestay is on top and clear of entanglement. From the cockpit, fit the step pins that stick out to either side of the mast foot into the slots of the tabernacle. You can carefully lay the mast back across the transom and walk forward to be sure the pins are in place. Then return to the back of the cockpit and lift, press the mast up to your shoulders. Scan the stays to be sure they aren't caught or about to be, then walk the mast up, watching your shrouds, the side stays, all the way up to the cabin. This is where you hop up onto the cockpit benches and onto the top.
I hope you closed the hatch before you got to this point. You won't enjoy falling into the cabin if you step wrong. Keep going until the mast is upright. If your shrouds, the side stays, are adjusted close to the right length, they should tighten up as the mast comes to vertical, but not keep you from coming all the way upright. Keep an eye on those turnbuckles. They can sometimes get twisted and the leverage of a twenty-four foot mast can bend them out of shape against the chain plates (the steel plates that hold the turnbuckles to the hull). Be patient and don't hesitate to lower the mast again to straighten everything back out, if something falls out of place.
Once the mast is vertical, be sure the tension on the shrouds is enough that the mast won't fall sideways. Now catch the dangling forestay and pull it tight, walking it to the bow. On level ground or at the dock, in water, this shouldn't require a lot of strength. So, if the forestay isn't long enough to catch the bow plate, you will have to adjust the turnbuckle or start over with an extention. If the backstay is pulled tight, but the forestay won't reach, adjust the backstay all the way out and try again.
There are a lot of guides and ideas to rig tuning. You will want to read up on that before you go for a sail. These directions are just to raise the mast, not on properly tensioning the rigging. I don't find it hard to do, that is essentially how I did it on my old Hobie, as well.
Another early step is to join the Mariner Class Association. I think the membership is still about $5 and includes a $5 discount for BoatUS membership. Here is the address. They are also a great group of sailors.
https://www.usmariner.org
Another site worth checking out is:
O'Day Mariner #1922 "Orion"
So glad to have you join us here. I will be happy to answer any questions you may have. I own a Mariner, but my sailing experience is on other boats. I'm still waiting for the time to fix mine.
-Will
