Rule 35A vs Attwood 4202-7

Buy the Rule 35A Rule-A-Matic bilge float switch, ASIN B000O8DA3M, when you want the mercury-free Rule float switch the family language calls Rule-A-Matic for automatic bilge-pump activation, with a marine-grade job for pumps and a removable-base servicing story on the Rule 35A family. Buy the Attwood 4202-7 float switch, ASIN B0000AZ5BK, when you want the sealed, mercury-free Attwood switch rated for 12/24V CE use, with about 36 inches of wire, actuation around 2 inches of water, a max of 12A at 12V or 6A at 24V, and a mount that can sit horizontal up to about 24 degrees. Both cards are float switches. Neither card is a bilge pump.

Short version. A Rule 800 and an Attwood Tsunami T800 are the pumps these switches can call. An Attwood 4505-7 and a SEAFLO are another pump pair. A SHURFLO and a Jabsco are fresh-water pumps, not bilge float switches. An HX890 and an M37 are handheld VHF radios. A UM385BK and a GX1400 are fixed VHF choices. Match B000O8DA3M or B0000AZ5BK before you match the word bilge.

The Rule title is a 35A Rule-A-Matic float switch, ASIN B000O8DA3M. Mercury free is the disposal sentence. Automatic bilge activation is the job: rising water lifts the float, the switch closes, and a wired bilge pump should run until the water drops. Marine-grade means a wet bilge, not a household sump label. Rule-A-Matic is Rule's phrase for this automatic float style. Removable-base servicing language on the 35A family is why owners clean the float without cutting the boat apart. A different Rule suffix is a different ASIN. A float switch is not a pump. The 35A only tells a pump when to try. Wire gauge, fuse size, and a pump rated for the switch's current are the electrical half. Mercury free does not mean oil, bags, and chips cannot jam the float. Clean the bilge.

The Attwood title is float switch 4202-7, ASIN B0000AZ5BK. Twelve and twenty-four volt CE language is the electrical range. About 36 inches of wire is the lead to plan for, not household lamp cord. Actuation at about 2 inches of water is the level sentence on a properly mounted float. Max 12A at 12V and 6A at 24V are the current ceilings. A larger pump needs a relay. Mounts horizontal up to about 24 degrees is the attitude window. Sealed and no mercury are the construction sentences. Sealed is not "ignore bilge sludge." A different Attwood part number is not this card. Place the switch where water actually collects in the boat's normal attitude, including on the trailer if that is how you store it.

Rule 35A is ASIN B000O8DA3M. Attwood 4202-7 is ASIN B0000AZ5BK. A bilge pump, a fresh-water pump, and a VHF radio are different cards.

Who should buy the Rule 35A, and who should buy the Attwood 4202-7?

Buy B000O8DA3M if you want the Rule 35A Rule-A-Matic float switch, mercury free, for automatic bilge activation, and the removable-base servicing story on the Rule 35A family matches how you maintain the boat. You already own, or you will buy, a bilge pump whose current draw fits the switch and the fuse. You will mount the float where water collects, not where the bilge looks tidy in a dry photo. You will test the float by lifting it with the battery on and the bilge dry enough to watch the pump spin.

Buy B0000AZ5BK if you want the Attwood 4202-7 with the sealed mercury-free switch, about 36 inches of wire, actuation around 2 inches of water, a 12A-at-12V or 6A-at-24V ceiling, and a mount that can sit horizontal up to about 24 degrees. You will size the pump and the fuse to those amp numbers. You will not hang the switch on a steep face past the attitude the card describes. You will keep oil and trash off the float so the 2-inch sentence can mean something.

Do not buy either switch instead of a pump. A Rule 800 or Tsunami T800 and an Attwood or SEAFLO pump move the water. The switch only closes a circuit. Do not buy a bilge float because you needed a fresh-water pump. A SHURFLO and a Jabsco are that other shelf. Do not buy a float switch because the radio is quiet. A handheld VHF and a fixed VHF are how you call for help after the bilge plan has already failed.

What the Rule 35A is actually for

The Rule 35A is an automatic float switch in the Rule-A-Matic family. Rising water lifts the float. The switch closes. A wired bilge pump should run. Falling water opens the switch. Mercury free is the construction claim that matters for disposal and for older boats that still hide mercury switches in corners. Marine-grade is the category for a wet bilge, not a laundry-room sump. Removable-base servicing language on the 35A family is the maintenance hook: clean the float, check the hinge, put the base back. A switch packed with fishing line will not float.

Rule's own pump cards are separate ASINs. Pair the 35A with a pump you can name and fuse. Automatic mode is not a reason to skip a manual bilge switch at the helm if your boat already has one. Automatic mode is the night watch when the boat is alone in a slip. Test it before you trust a holiday weekend. Lift the float. Hear the pump. Release the float. Hear it stop. If it does not stop, the wiring or the switch is stuck closed, and a pump that runs dry can burn.

Do: match B000O8DA3M and clean the float on a schedule. Don't: treat the switch as a pump. Don't: bury it under a oil pad that never lets the float rise. Don't: ignore a pump that runs without water after you release the float.

What the Attwood 4202-7 is actually for

The 4202-7 is Attwood's sealed, mercury-free float switch on this card. Twelve and twenty-four volt CE language covers common small-boat banks. About 36 inches of wire is the lead to route with drip loops and chafe protection, not a clothesline across a hot engine. Actuation around 2 inches of water is the level to plan for when you place the switch in the lowest wet pocket that still lets the float move. Max 12A at 12V and 6A at 24V are hard ceilings for the switch contacts. A larger pump needs a relay so the switch only sees coil current.

Horizontal mounting up to about 24 degrees is the attitude window. A vertical bulkhead mount outside that story is a different product or a different install. Sealed means the switch body is built to keep bilge water out of the contacts. It does not mean the float can fight a bag of leaves. Keep the area clear. Test the same way: lift, pump runs, release, pump stops. If the boat is on a trailer with the bow high, water may sit away from the switch. Place it for the attitude that matters when the boat is in the water, and know how the trailer sits if you store it that way in the rain.

Do: fuse the positive near the source and respect the 12A / 6A ceilings. Don't: splice the 36-inch lead with unprotected butt connectors in the bilge. Don't: mount past the ~24° horizontal story. Don't: size a pump that already exceeds the switch and skip the relay. A relay lets the float see a small coil load while the pump takes battery current through contacts sized for the motor. That is ordinary marine practice when the pump label already outruns 12A at 12V. Read the pump amp draw cold and running. A stuck impeller can spike the load past the number on the carton.

How to wire and place either switch

Kill the battery switch before you cut into a bilge circuit. Fuel vapor and a spark are a pair you do not want. Route the float leads with drip loops. Support the wire so the float hinge is not carrying the cable. Fuse the pump circuit. Use marine-grade connectors, not household wire nuts. Place the switch in the lowest point where the float can still swing, away from a wash-down stream that fools it and away from a spinning shaft. Test after every haul-out. Automatic is not unattended forever. A cracked hose can beat a small pump. Keep a manual override and a habit of looking after a storm.

What actually fails on these two cards

The Rule card fails when the 35A is treated as a pump, when a different Rule model is ordered from a matching photo, when the removable base is never cleaned, when an old mercury switch is left as a "backup," or when the fuse is oversized. The Attwood card fails when 12A / 6A is ignored without a relay, when the ~36-inch wire is stretched with junk splices, when a dry-shelf mount is expected to see 2 inches of water, when the mount leans past about 24 degrees, or when sealed is read as maintenance-free forever. The shared failure is a dirty bilge and a skipped lift test. Oil, bags, and chips jam floats. Clean before you blame the brand.

What this comparison is not

It is not a bilge-pump review, a fresh-water pump review, or a VHF radio review. It is not a price quote. Use the buttons for the live switch listing. It is not a promise that automatic mode replaces walking the dock after a storm. Both cards are mercury free. It is not a reason to skip fuses, drip loops, or a pump sized to the switch. The job is a boat bilge, not a house sump.

So which float switch should you buy?

Buy the Rule 35A Rule-A-Matic, ASIN B000O8DA3M, when you want the mercury-free Rule float switch for automatic bilge activation and the removable-base servicing story on the 35A family. Buy the Attwood 4202-7, ASIN B0000AZ5BK, when you want the sealed mercury-free switch with about 36 inches of wire, actuation around 2 inches of water, 12A at 12V or 6A at 24V, and a horizontal mount up to about 24 degrees. Pair either one with a real bilge pump, a real fuse, and a lift test before you leave the boat alone.