Yamaha F90

Continuous use — at every fill-up and after every outing

• Add Yamalube Ring Free PLUS fuel additive at every fill-up
• Treat every tank with Yamalube Fuel Stabilizer & Conditioner PLUS
• Flush the cooling system after each use, especially in salt or brackish water
• Check the power trim and tilt fluid level, and top up with Yamalube Performance Power Trim & Tilt Fluid if the system will not hold a tilt
• Apply Yamalube Yamashield corrosion-protection spray
• Before going out, inspect the outside of the lower unit for damage and clear any fishing line or debris from the propeller shaft
• During wash-down, brush growth off the anodes — an anode covered by growth, paint or coating cannot do its job

After the first 20 hours — new-outboard break-in service

• Change the engine oil and replace the oil filter
• Replace the lower-unit (gearcase) lubricant, fitting new crush washers to the drain and vent screws
• Replace the external 10-micron fuel/water separating filter
• Replace the primary on-engine fuel filter element

Every 50 hours

• Replace the external 10-micron fuel/water separating filter — or sooner if you take on a bad tank of fuel

Every 100 hours or annually, whichever comes first

• Change the engine oil and replace the oil filter
• Replace the lower-unit (gearcase) lubricant — the drain and vent screw crush washers are single-use and must be renewed every time
• Replace the primary on-engine fuel filter element
• Pull the spark plugs and check them for colour and wear — they should be light brown with relatively sharp edges — and replace as necessary
• Check the magnetic gearcase drain screw while the lubricant drains: fine metallic dust is normal, but larger chips mean a dealer should look for internal damage

Every year — water pump inspection

• Inspect the impeller and water pump assembly, whether the engine runs in salt, brackish, turbid or fresh water
• Replace the impeller or the whole water pump assembly rather than attempting a repair, and never turn the crankshaft or drive shaft counter-clockwise while the pump is apart

Every 300 hours — authorised Yamaha dealer

• Have an authorised Yamaha Marine dealer replace the Vapor Separator Tank (VST) filter

Every 1000 hours or five years, whichever comes first

• Replace the timing belt

Dealer-performed checks — interval per your engine's owner's manual

• Have an authorised Yamaha Marine dealer check the valve clearance
• Have an authorised Yamaha Marine dealer inspect the timing belt

On condition — anodes

• Replace the anodes when they are about half gone — this is owner-serviceable on most models
• Never paint or coat an anode, and brush growth off it at each wash-down: a covered anode cannot protect the engine

Before winter storage or lay-up

• Change the engine oil and replace the oil filter
• Replace the lower-unit (gearcase) lubricant
• Replace the external 10-micron fuel/water separating filter and the primary on-engine fuel filter element
• Treat the fuel with Yamalube Ring Free PLUS and Yamalube Fuel Stabilizer & Conditioner PLUS
• Fog the engine with Yamalube EFI Engine Storage Fogging Oil
• Flush the cooling system and apply Yamalube Yamashield

Yamaha publishes two different spark plugs for this engine

The F90 model page on Yamaha's site specifies an NGK LFR6A-11. Yamaha's own 2024 Maintenance Matters brochure specifies an LFR5A-11 on the row covering the F75 and F90, and again on the row for the 65 hp jet-drive F90. Both are Yamaha documents and neither is obviously superseded, so this page lists both rather than picking the prettier one. The practical answer is to read the plug you take out and check it against the manual for your engine's serial number before buying a set of four.

The F90 shares a powerhead with the F115, which is why parts lists blur

F75, F90 and F115 are all the same 1.8-litre in-line four, and Yamaha lists one oil filter, one on-engine fuel filter element and one 100-hour service kit across all three. That makes it tempting to borrow an F115 parts list wholesale — and two numbers on it are wrong for an F90. The spark plug differs, and so does the gearcase: 22.7 fl oz on an F90 against 25.7 fl oz on an F115. Share the filters, not the capacities.

A jet-drive F90 is a 65 hp engine with no lower unit to service

Yamaha sells a jet-drive version of this engine, rated 65 hp at the pump, with a model code ending JB. Everything above the transom is the same engine on the same 100-hour cycle, but there is no gearcase, so the lower-unit lubricant and its crush washers simply do not apply — the jet pump has its own service points and its own grease. If your clamp-bracket label reads F90JB, skip the gearcase items on this page and work from the manual section for the jet drive.

The cheapest filter on the boat has the shortest interval

The external fuel/water separating filter in the line between tank and engine runs on a 50-hour clock — twice as often as anything else — and Yamaha says to change it immediately after a bad tank of fuel regardless of hours. There is a second filter on the powerhead at 100 hours and a third inside the vapour separator tank that a dealer changes at 300. Owners who service the engine-mounted filter and forget the in-line one end up sending water and debris to a filter that was never meant to be the first line of defence.

Yamaha's own maintenance hub. The replacement-schedule chart here uses ● to mean “refer to your Owner's Manual or consult your dealer” — it is not the same as a tick, and several 100-hour rows carry it.

Yamaha's own bulletin for the three second-generation 100-hour kits: what each kit contains and the exact model codes it fits. It is also where Yamaha states the cadence in its own words — every 100 hours or each year, whichever comes first.

The bulletin for the four earlier 100-hour kits, which cover model codes the second-generation kits do not. Worth reading if your clamp-bracket code is missing from the April 2026 list: the first-generation kits hold a different set of parts — impeller, thermostat, anode, trim tab and plugs rather than the oil filter and drain-plug gaskets.

Yamaha serves the manual against your engine's Primary ID (model code, shaft length and serial number), which is on the label on the clamp bracket. Intervals Yamaha does not publish publicly — valve clearance is the one that matters here — are in that manual.