Motor flushing

[AaronCarl]

I have a new 2024 Yamaha 255 FSH boat we just picked up and it will be staying in the water while we are in the keys for a month can I flush these engines while it is in the water

Thank you

 

[14SX190]

Hi,

Welcome to the greatest site.

Watch out for the shallows. What parts in the Keys?

You can flush it with fresh water if it's on the lift.

Congrats on new boat

 

[AaronCarl]

Duck Key,
I dont have a lift only a slip

Thank You

 

[FSH 210 Sport]

You can flush it while it’s sitting in the water, but salt water will come back up water inlet from the jet pump. I’m sure that will help some as it will push salt water out of the engine. Just be sure you follow the same procedure of engines on water on then water off then quickly engine off. The only way to really flush them while sitting on the water is to have valves on the water inlet from the jet pump Where you can cut off the cooling water from the jet pump. How long do you plan on having it sit saltwater?

 

[TeeNGee]

We just got back from a week in Islamorada. The Sargasso weed was really bad in the ocean and in the bay near the cuts. Even after multiple "Crazy Ivans" I got over heat alarms at low speed. No problems above 3,000 rpm. No problems after we got home.
Here is what I did to flush while still floating:

Thread 'Pump Isolation Valves'

Oct 25, 2024

I just finished installing a pair of isolation valves between the pumps and where the fresh water flush connects to the cooling lines.
The main reason I did this was so I could flush both engines at the same time. The hose I use to flush the engines did not have enough flow to flush both engines because of the amount of water that just runs out of the pump. When closed these valves eliminate the reverse flow out the pump. After flushing, opening the valves allows the engines to drain back through the pump.
A second benefit is the ability to flush the engines while still in the water...

• TeeNGee
• Replies: 7
• Forum: Yamaha Center Console FSH 19x, 21x, 22x, 25x

• 

Based on this thread you could clamp the line highlighted in the picture in red and flush with the engine off and not risk hydrolock. Your call on this one.

Thread 'Cooling water flow & hydro-locking'

Jun 18, 2025

Does the water highlighted in blue cool the exhaust manifold and enter the head without mixing with exhaust gases?
Is the red highlighted water flow the only water that mixes with the exhaust gases and subsequently cools the remainder of the exhaust (water lock, resonator, exhaust valve, & associated hoses) and out through the exhaust valve?
If this is the case, the water lock would need to fill to the level of the exhaust valves before water could cause a hydro-lock.
Am I interpreting these schematics correctly?

• TeeNGee
• Replies: 10
• Forum: General Discussion

One last warning in shallow water, ONLY MOVE FORWARD. In Neutral and reverse you risk sucking up sand.

 

[AaronCarl]

About 3 weeks

 

[TeeNGee]

Things will start to grow on your boat.
We were only in the water 5 days.

 

[AaronCarl]

Yes I have a beavertail skip I normally bring down and it gets alge growing on it