255 fsh E cooling system clamping

[skyhighdiver]

OK somebody that’s mechanically smarter than me. This is been asked over and over and nobody has yet to post a photo or a correct answer . I’m going to make it easy. Here is the 255 fsh E cooling system from the service manual. Let’s not get into the reasons ,why but if you’re going to tow the boat or go faster than wake speed with one engine off, are you going to need to crimp off water intake line to the engine that is off to prevent filling cylinders and Hydro lock. So the question I have is do you have to pinch off just the green location or do I have to pinch off both lines as in the red location. Or the obvious answer would be to pitch it off at the yellow location if that’s accessible, knowing this could help save somebody’s engine.

 

[MT FSH]

OK somebody that’s mechanically smarter than me. This is been asked over and over and nobody has yet to post a photo or a correct answer . I’m going to make it easy. Here is the 255 fsh E cooling system from the service manual. Let’s not get into the reasons ,why but if you’re going to tow the boat or go faster than wake speed with one engine off, are you going to need to crimp off water intake line to the engine that is off to prevent filling cylinders and Hydro lock. So the question I have is do you have to pinch off just the green location or do I have to pinch off both lines as in the red location. Or the obvious answer would be to pitch it off at the yellow location if that’s accessible, knowing this could help save somebody’s engine.View attachment 204636

Yellow would be ideal, but you can’t reach it for both engines through the small door. Red would be next best if you have enough room to get it in the engine bay. This was bothering me so I removed the horizontal panel above my cleanouts. I’ll take some photos when I am back up at my boat storage.

 

[FSH 210 Sport]

Pretty sure A goes up to the flushing connector.

The red line is where you’d want to clamp off those two lines.

 

[TeenGee]

I installed valves in the yellow location.

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

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