Rule-Mate Automatic Submersible Bilge Pumps 12V RM500B- 500GPH with Auto Sense
- 500 GPH rated flow, listed as 8.33 gpm
- 12 volt corded electric pump
- Switches on at 2 inches of water, off at 3/8 inch
- Backup cycle every 2.5 minutes if the sensor is blocked
- Thermal cut-off and backflow prevention
- Threaded discharge, body 8.5 x 6.75 x 3.75 inches
- 16 ounces item weight
Last refreshed Oct 2, 2026 · Based on the Amazon listing and published specifications, not hands-on testing.
A compact automatic bilge pump for small boats that need hands-free water removal at a modest flow rate. The lifting height is not given, so check it against your discharge run.
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ASIN: B07L3JG61YModel: RM500BCategory: Bilge Pumps
Overview
A boat owner with a cramped bilge gets a submersible pump that starts itself when water reaches a set level and stops once the bilge is nearly dry. Auto Sense Intelligence handles the switching, and a threaded discharge connects the outlet.
Rule-Mate adds protection against the usual failure points: a blocked sensor, overheating and water running back into the bilge. That makes it a low maintenance choice for a weekend boat. The limitation is the flow class, the smallest of the three sizes in the range, and the missing lifting height.
Who it's for
Small boats with limited bilge space where a pump must work unattended between trips. Owners of bigger hulls, or anyone who must pump up a long discharge run, should choose a larger model.
Pros and cons
- Fully automatic level sensing
- Backup cycle if sensor blocked
- Thermal cut-off against overheating
- Built-in backflow prevention
- Lifting height not listed
- Smallest flow size in the range
- Hose or fitting size unstated
Performance notes
A level sensor starts the pump at a set water depth and stops it near the bilge floor, so it needs no float switch or manual control. If the sensor is blocked the pump cycles on a timer instead, which prevents a silent flood. Hidden air vents clear airlocks, and the thermal cut-off protects the motor if it runs dry or overheats.
Specifications
| Brand | Rule |
|---|---|
| Model | RM500B |
| Dimensions & fit | |
| Item Dimensions L x W x H | 8.5 x 6.75 x 3.75 inches |
| Weight | 16 ounces |
| Capacity & performance | |
| Flow Rate | 8.33 gpm (500 GPH) |
| Power & efficiency | |
| Power Source | Corded electric |
| Voltage | 12 volts |
| Construction & materials | |
| Material Type | Plastic |
| Color | White |
| Warranty & support | |
| Manufacturer Warranty Description | Manufacturer warranty |
Closest rivals on specs
SEAFLO 06 Series Automatic Submersible Bilge Pump- Flow Rate 8.33 vs 12.5 gpm (-33%)
Attwood WaterBuster Portable Submersible Pump- Flow Rate 8.33 vs 3.33 gpm (+150%)
Frequently asked questions
How do I connect the discharge on the Rule-Mate RM500B?
The pump uses a threaded discharge system described as quick to install. The listing does not give the thread or hose size, so check the outlet before buying fittings.
What happens if the RM500B sensor gets blocked?
A built-in backup mode cycles the pump every 2.5 minutes so water is still removed. The description presents this as protection against flooding.
Is the RM500B a manual pump?
No. It is a level sensing automatic pump that switches itself on at 2 inches of water and off at 3/8 inch, so no float switch is described.