Raymarine i40 vs i50 Depth: which instrument should you buy?

For a simple SeaTalk installation, consider i40 Depth; for a SeaTalkng-based refit, start the comparison with i50 Depth. Both provide a dedicated depth readout. The purchasing decision is about the complete working installation and what you can sensibly retain, rather than treating the more expensive display as automatically more accurate.

#What changes between them?

Shaded rows contain different values. On a small screen, scroll the table; model names stay visible within it.

Sources: Raymarine’s Australian i40 Depth and i50 Depth pages. Prices include GST and were checked on 3 October 2026; they are manufacturer listings, not guaranteed stock or installed quotes. Each page also offers transducer packages. Identify the exact kit before comparing prices.

#Keep the useful parts of your existing system

Before replacing anything, photograph the rear of the instrument, cable labels and transducer identification. Record whether the old instrument drives a sensor or only repeats depth from elsewhere. That distinction changes the replacement list: removing a display that also drives the transducer can remove the source of depth for other devices.

Have the installer confirm retained-sensor compatibility in writing. A connector that can be adapted mechanically does not by itself prove the electrical and acoustic match. If the sensor is sound, retaining it may avoid hull work; if it is damaged or poorly located, a new display will not solve the underlying problem.

#Dedicated readout or network repeater?

A dedicated number beside the helm can make depth easier to glance at while the chartplotter shows a chart or radar. That is a useful ergonomic reason to buy an instrument, independent of its screen size. Check readability from your normal steering position, with the lighting levels you use at night.

Raymarine documents master/repeater use for these families. If the display repeats a network source, ask what it shows when that source or the backbone loses power. An additional display is not necessarily an additional sounder. Plan backup around independent sensors and power paths if redundancy is the objective.

#Budget beyond the faceplate

A display-only price is a fair comparison only when both candidates can use the equipment already aboard. Otherwise include the sensor, network or converter, cable route, panel work and commissioning. The differently shaped housings also mean a replacement may need a backing plate or changes to the instrument panel.

Ask for the supplied transducer part number rather than accepting “depth kit” on the quote. For an older system, include time to identify and test existing wiring. For a new installation, include access to the sensor position and any haul-out. Those costs can change the value judgement more than a retail discount.

#Set up the number you want to see

Decide whether the instrument should show depth below the sensor, water depth or clearance below the keel. Measure the relevant distances, follow the instrument’s offset convention and verify the result independently in suitable conditions. Label the convention so another helmsperson does not assume a different meaning.

Our choice would be i40 for a compatible, modest SeaTalk repair and i50 as the first candidate for a SeaTalkng installation. If the job is a fully independent simple sounder, also read the NASA Marine profile. The cruising depth-sounder shortlist explains the alternatives without mixing navigation instruments with fishing sonar.

#Example: retain a SeaTalk installation or rebuild the instrument network

A yacht with functioning SeaTalk instruments and a failed depth display should first identify the sensor and inspect the wiring. If an i40 replacement is supported and restores the intended function, it can be a rational budget repair. An i50 proposal becomes more relevant when the owner is deliberately moving to a supported SeaTalkng arrangement or needs a different instrument presentation. Neither route should assume the old transducer is suitable without identifying it.

Price both routes with the same boundary. Include any converter, network parts, panel alteration, sensor replacement and hull access. A display-only price difference is not the cost of changing the boat. A planned haul-out may alter the timing, but it should not justify retaining an unreliable depth system until an unsuitable voyage.

#Commission the reference, not just the number

The displayed depth needs an explicitly labelled reference: below transducer, below waterline or below keel, according to the instrument’s supported setup and the owner’s choice. Establish the actual geometry and follow the manual’s sign convention. Different instruments can use settings differently, so do not copy a numerical offset from a previous brand without checking what it means.

For an illustrative check, a downward sensor reporting 3.2 m below itself with the keel extending 1.1 m below that sensor implies 2.1 m of static clearance below the keel. It does not include allowances for motion, squat, bottom uncertainty or the limitations of the observation. The arithmetic is a check of the reference, not a safe-passage recommendation.

Shaded rows contain different values. On a small screen, scroll the table; model names stay visible within it.

If the boat has multiple depth displays, verify that their differences are understood rather than forcing their numbers to agree blindly. For a catamaran, identify the hull as well as the reference. Use the sailing depth-refit example to organise the job and the 32-foot yacht plan to keep the screen decision in proportion to the rest of the budget.