100TECH Marine Fuel Sending Unit 8.5in 240-33ohms - Durable Reed

In this review of the 100TECH Marine Fuel Sending Unit 8.5in, the bottom line is simple: this is a practical, durable replacement sender for boat, truck or RV fuel tanks where a reliable reading matters more than bells and whistles. The reviewer found it especially suited to owners who want a direct OEM-style arm replacement with a robust reed switch mechanism and stainless construction. Installation is straightforward and the unit delivers repeatable readings for common tank sizes, making it a solid choice for routine fuel and water level sensing.

Key Features

• Imported OKI reed switch: Provides greater durability and longevity compared with thick-film swim arm senders, so readings remain reliable over time.
• Stainless construction: Resists corrosion in marine environments, helping the sender hold up on boats and in wet conditions.
• Direct replacement fit: Uses an SAE 5-hole mounting pattern so it replaces common OEM arm-type fuel senders without modifying the dash or gauge wiring.
• Complete installation kit: Ships with a cork gasket, five mounting screws and illustrated instructions to make the roughly 15 minute installation simple and safe.
• Wide fluid compatibility: Rated for diesel, gasoline and water, so it can be used as a fuel or water level sender in many vehicle and marine applications.
• 240-33 ohm output: Outputs 240 ohms at empty and 33 ohms at full, compatible with gauges designed for that non-linear range.

Who It's For

This sending unit is a good choice for boat owners, RV and truck owners, and DIY mechanics who need a durable, OEM-style arm replacement that installs quickly and gives consistent readings. It is particularly useful for medium and larger tanks where a stainless arm and reed switch add confidence in a marine environment.

Those who should look elsewhere include users who require exact linear output curves for custom electronic gauges or those who need lengths other than the listed range without consulting the seller; specialists with custom tanks may need a custom unit rather than this direct-replacement design.

Pros & Cons

Pros

• Sturdy OKI reed switch and stainless build give improved durability over swim arm types.
• Includes gasket, screws and clear instructions so installation is quick and low-odor.
• Direct SAE 5-hole replacement simplifies swapping into many OEM mounting patterns.
• Works with diesel, gasoline and water, adding flexibility across vehicles and boats.

Cons

• Output is non-linear 240-33 ohms which is ideal for compatible gauges but not for setups requiring a linear signal without calibration.
• Float diameter requires a roughly 1.50in hole if routing through a new deck opening, which may be inconvenient for some installations.

Specifications

Brand	100TECH
Length	8.5in (216mm)
Signal output	240-33 ohms (240 empty, 33 full)
Mounting pattern	SAE 5-hole
Materials	Stainless construction with OKI reed switch
Included items	Cork gasket, 5 mounting screws, instructions
Float diameter	1.38in (35mm); drill hole ~1.50in recommended

Our Verdict

The 100TECH 8.5in fuel sending unit is a practical, cost-effective OEM-style replacement that excels where reliability and corrosion resistance matter. It suits boat and vehicle owners who want a straightforward swap-in part with a durable reed switch and clear installation kit. For those with compatible gauges and standard tank depths, it represents strong value and dependable performance.

Frequently Asked Questions

Will this work with diesel and gasoline?
Yes. The unit is specified for diesel, gasoline and water, so it can be used as a fuel or water level sender for most common applications.

What does 240-33 ohms mean?
It means the sender reads about 240 ohms at empty and about 33 ohms at full; the output is non-linear and matches gauges designed for that range.

How deep can the sender be used?
Measure tank depth from the top and subtract 1in to avoid the arm hitting the bottom; contact the seller if you need lengths outside the standard range.