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Yamaha Outboard Maintenance

This is important when you go to look up parts.  Partsvu has a link to the “Genuine Yamaha parts lookup” which is hosted by Yamaha. (


Step 1 – Outboard

Step 2 – 300hp

Step 3 – F/LF300A (V6 4.2L) DEC. <-- Digital electronic control (electronic throttle).

Step 4 – F300UCA 0119 <-- January 2019

Step 4 will require that you know the manufacture date on your engine. My boat is a 2021 RT27-OB, the engine was new when I got the boat. Yet the F300 was manufactured in October 2019. You will need to look at your engine, starboard side, you'll find a sticker under the cowling that will have the mfg. date.


I look for F300UCA in the drop-down list at step 4. I see a F300UCA 0119 and a 0120. (January 2019, and January 2020). Since my motor was made in October 2019, I must select the 0119.

Yamaha has a decoder ring for their part numbers. F is four-stroke standard rotation. LF is left-hand rotation four stroke. 300 is HP. The U means 30” shaft (X would be 25”). This is the height of the lower unit.  C means command link control (the Yamaha engine display in your boat).  “A“ is the product generation. F300UCA.


I put together a full spreadsheet for routine maintenance, which includes the F300, T9.9 and F2.5 (dinghy motor).

Some important things to note with respect to the Yamaha service manual.

  • The head gaskets replacement, the service manual calls out for Threebond 1280B sealant.  Yamabond 4 Marine is the Yamaha OEM substitute for Threebond 1280B. You’ll only need this to access 4 of the 8 crankcase anodes to replace around 300-500 hours.

  • Grease A and D are the same.  Use Yamaha Marine Grease wherever the manual calls for either grease A or grease D.

Yamaha uses Yamalube Marine Gear Case Oil for most of their outboards. The F300, however, uses a special formula (Marine Gear Case Oil HD). The T9.9 kicker and F2.5 use the standard marine gear oil. The F300 uses the HD marine gear oil.

Other items to mention: the T9.9 kicker has no oil filter.  There’s an oil strainer in the T9.9 that’s not serviceable per routine maintenance. The Kicker maintenance is lower gear oil, impeller, oil change, two spark plugs and one thermostat. There’s 1 anode in the T9.9 (cylinder head anode).


The correct service manual can be purchased directly from Yamaha Pubs.  This is not the same as the owners guide.

F300 – LIT-18616-F2-25 (main engine)

T9.9 – LIT-18616-03-46 (kicker) 

They don't print the manual until you order it.

My objective around routine maintenance is to make it like a NASCAR pitstop. In and out quick, routine.


Starting out, the simplest approach is this.

Set up an account with Partsvu, so you can drop stuff in your "wish list", which makes reordering easier. For the 20 hour maintenance, you'll start with the 20hour maintenance kit for the Yamaha F300. It'll come with oil, filter, fuel filters, lower gear unit oil and the pump needed to install the lower gear oil. 

In addition to the 20 hour kit, you'll want a can of Yamashield Rust and Corrosion Protectant.

I put in Yamaha fuel stabilizer and conditioner when I know gas is going to sit in the tank for several weeks.  It’s 1:3 for gas, so 50oz per 150 gallons of fuel and they’re 32oz bottles.

I put ½ a bottle of Yamalube Ring Free Plus in every 50 hours. It’s spendy stuff.  But the ratio is 1:10 for gas.  So, 15 oz per 150gallons of fuel and they’re 32oz bottles.

After that, you're good for another 100 hours or 1 year, whichever comes first.

The Yamaha F300 100 hour kit from Partsvu.

The 20 hour service on the T9.9 kicker is to simply change the engine oil, change the lower gear unit oil.  There’s no oil filter to change.

Yamaha F300 - Routine Maintenance Checklist

Every 100 hours

  • Oil and Filter (Engine) - Replace

  • Spark Plugs - Inspect/Replace

  • Fuel Filter - Replace Primary

    • On the front of the engine

  • Fuel Filter - Replace Secondary

    • In the cockpit center lazarette

  • Grease steering zerk fittings

  • Change lower unit gear lube oil HD

  • Transom Engine Anode - Inspect

    • Replace if 50% worn (qty 1)

  • Trim Tab Anodes - Inspect

    • Replace if 50% worn (qty 2)

  • Propeller Anode (skeg)- Inspect

    • Replace if 50% worn (qty 1)

  • Add Yamaha Ring Free treatment into gas tank

    • (10:1 mixture)

  • Add Yamaha fuel treatment into gas tank

    • (3:1 mixture)

  • Yamasheild Rust and Corrosion Protectant

    • (spray all over engine)

  • Remove Propeller

    • (inspect for fishing line wrapped around spline)

  • Water Impeller - Check

    • (Replace if necessary)

  • Thermostat (2) - Check

    • (replace if necessary)

Every 300 Hours

  • Perform 100 hour maint.

  • Water Impeller and housing

    • Replace

  • Fuel Pump

    • Check/Replace (I’ll have the dealer perform this)

  •  Anodes (Cylinder head exhaust passage)

    • Inspect/Replace if 50% worn (qty 8)

  • Anodes (Thermostat)

    • Inspect/Replace if 50% worn (qty 2)

Every 500 Hours
Note: I plan on having a Yamaha dealer do the 500 hour service

  • OCV Filter

  • Valve Clearance

  • Anodes

    • Cylinder Head

    • Cylinder Block Thermostat portion

    • Oil cooler cover

    • Exhaust guide


Good video’s How-To for DIY on the Yamaha F300 and F250.  
(The Yamaha F225/F250/F300 are nearly identical. They all are 4.2l V6, and share the exact same Yamaha Service Manuel. (Part number: LIT-18616-F2-25 for the service manual). For detailed engine schematics that references OEM Yamaha parts (with part numbers) I use partsvu dot com.

I've not been able to find a youtube video on the 2 anodes that are under the thermostats yet. I may have to figure that one out and make my own video for it. (There is an anode just under the thermostats inside the engine that require servicing as well). But for all the other routine maintenance, here's some vid's on how-to that I found helpful.

Yamasheild - Corrosion and protectant

Yamaha Grease Points (steering and trim/tilt)


F300/F250 Thermostats replacement (qty 2)

F300/F250 Crankcase Anodes (qty 8)

F300/F250 Power Trim and Tilt Unit


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