Raymarine ST900 Speed/Temperature Low Profile Thru-Hull Transducer, For Airmar P120/B120, 0.3-45 Knots, Analog Output

Overview

The Raymarine ST900 is a low profile thru-hull speed and temperature transducer for boats that need responsive analog speed data with water temperature from a retractable sensor body. It records speed and temperature, works through a 51 mm (2 in) hull opening, and reads speed from 0.3 to 45 knots, with a water temperature range of -10°C to 40°C.

The ST900 uses Raymarine's Gen2 paddlewheel for better startup response and smooth readings across the speed range. The housing sits nearly flush with the hull, extending only 5 mm (3/16 in) outside the surface, so it keeps drag low on sailing yachts and powerboats.

A retractable insert makes paddlewheel cleaning and inspection more practical while the boat is in the water. The valve assembly helps limit water entering the bilge when the insert is removed, and the transducer core can retrofit into existing Airmar P120 and B120 housings.

Key features

• Speed and fast-response water temperature sensing from one low profile thru-hull transducer.
• Gen2 paddlewheel starts reporting from 0.3 knots and maintains speed output through 45 knots.
• Analog output for Raymarine instruments including i40, i50, iTC-5 and legacy systems.
• Retractable insert gives access to the paddlewheel for cleaning and routine service.
• Valve assembly helps reduce water ingress into the bilge when the sensor insert is removed.
• Nearly flush housing extends 5 mm (3/16 in) outside the hull to help reduce drag.
• Retrofits into existing Airmar P120 and B120 housings for many upgrade or replacement installations.

Variants

This ST900 range is offered in three configurations, with the main differences being housing material and cable length.

The plastic versions are listed for fiberglass or metal hulls, while the bronze version is listed for fiberglass or wood hulls. All three versions share the same ST900 speed and temperature function, low profile thru-hull mounting style, analog output, 51 mm (2 in) hole size, and 0.3 to 45 knot speed range.

• E70673: Plastic housing with 13.7 m (45 ft) cable. This version suits installations where a plastic thru-hull is appropriate and the instrument run does not require the longer 20 m cable.
• E70674: Plastic housing with 20 m (65 ft) cable. This version gives extra cable length for longer routing paths from the thru-hull location to the instrument system.
• E70686: Bronze housing with 13.7 m (45 ft) cable. This version uses a bronze thru-hull body and is listed for fiberglass or wood hull applications.

Installation and fit

This is a thru-hull transducer, so the hull material, existing housing, cable route, and service access around the mounting location should be checked before ordering. The 51 mm (2 in) hole size and retrofit compatibility with Airmar P120 and B120 housings make it a practical replacement path on boats already using those housings.

The low profile body works well where drag matters, such as sailboats, performance cruising boats, and powerboats where clean water flow across the paddlewheel helps maintain consistent speed readings. It should be installed where the hull shape gives the sensor a steady flow of water and where the insert can be reached for cleaning.

System integration

The ST900 outputs analog speed and temperature data for compatible Raymarine instrument systems. It is a good match for boats using Raymarine i40, i50, iTC-5 or supported legacy instrument setups rather than a networked smart transducer connection.

The cable length should be matched to the route from the thru-hull position to the instrument interface, allowing for service loops and safe routing away from sharp edges, high heat, and moving equipment.

Maintenance and care

Paddlewheel speed sensors need occasional cleaning, especially in saltwater, warm water, or areas with fouling growth. The retractable insert helps make that service easier, and the valve assembly helps reduce the amount of water that enters the bilge during removal.

For dependable readings, keep the paddlewheel free to spin and inspect the housing during regular haul-out or service intervals. This unit is well suited to owners replacing an older analog speed sensor or upgrading an existing P120 or B120 installation while keeping the same general thru-hull format.

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Returns may be requested within 30 days of receiving your order. Items must be unused, uninstalled, unaltered, and returned in their original packaging with all tags, packing materials, blank warranty cards, manuals, instructions, accessories, and included items. Certain products, including installed or used electronics, electrical components, lighting, consumables, custom or special-order items, cut-to-length products, safety equipment, and merchandise exposed to water or marine conditions, may not be eligible for return.

To request a return, sign in to your account and select the applicable order and items, and submit your request for review. Eligible unfulfilled items may also be submitted for cancellation within 1 hour of placing the order. Returns or cancellations are not considered approved until you receive confirmation from Apollo Lighting. Please do not ship or drop off merchandise before receiving return approval and instructions.

Customers are responsible for arranging and paying for return shipping unless the return is due to an error by Apollo Lighting or the item is verified as defective, damaged, or incorrect. Missing, damaged, defective, or incorrect items must be reported within 2 business days of delivery, and photos or other documentation may be required for review. If the issue is verified, Apollo Lighting may provide or reimburse return shipping and issue a replacement or refund depending on the circumstances. International customers are responsible for return shipping, duties, taxes, customs charges, brokerage fees, and other costs associated with an international return.

After your return is received and inspected, approved refunds are issued to the original payment method and may take 5-7 business days to appear after processing. Original shipping and handling charges are nonrefundable, and the value of any included free items that are not returned may be deducted from the refund. Apollo Lighting does not charge a standard restocking fee on eligible returns. Returns that are incomplete, damaged, installed, used, altered, improperly packaged, or otherwise do not meet the eligibility requirements may be refused. We recommend using a trackable and appropriately insured shipping service for all customer-arranged returns.

For assistance, contact info@apollolighting.com or call +1 (954) 375-0100.

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Many products sold by Apollo Lighting include a manufacturer's warranty covering defects in materials or workmanship. Warranty terms vary by brand, product category, and model, so eligibility, coverage duration, exclusions, and available remedies are determined by the applicable manufacturer. We recommend reviewing the warranty information provided with your product before installation or use, especially for marine electronics, navigation equipment, lighting, electrical systems, pumps, safety equipment, and other specialized marine products.

If you need warranty service, the claim must follow the process established by the manufacturer, authorized service center, or designated warranty provider. You may be asked for proof of purchase, a serial number, product registration, photos, maintenance or installation records, or other documentation. Apollo Lighting does not determine or modify a manufacturer's warranty coverage or final claim decision, but we are happy to help provide purchase information and direct you to the appropriate manufacturer or warranty resource.

Keep your receipt, product documentation, serial number information, and original packaging when practical. Damage caused by normal wear, misuse, improper installation, insufficient maintenance, corrosion, impact, unauthorized modifications, electrical issues, or operation outside the manufacturer's specifications may not be covered. Warranty claims are separate from standard returns, so a product that has been installed, used, or exposed to marine conditions may no longer qualify for return while still remaining eligible for evaluation under the manufacturer's applicable warranty.

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