Exhaust Flushing Question..

[CJM]

The engines are 2000 Mercruiser 7.4 Horizons (FWC) InBoards, The exhausts are raw water cooled. There is a connection for a garden hose connected to the riser (elbow) with a blue cap on it. I just need to know the exact steps to flush.... Do you close the seacock and then turn the garden hose on ? Do you start the engines or just flush with them off?

 

[PMC]

If you have a picture of the exhaust and riser layout, as it sits inside the boat will help.

With the water inlet on the riser, do not run the engine with a closed seacock. This will run the impeller dry, and it will burn up in short time.

Are the risers the highest point in the exhaust? Meaning does water have to travel up, maybe up the lift muffler? Without the engine running you can flush the exhaust, but ONLY if it will safely drain away from the engine. What you don't want is filling an engine cylinder with a garden hose to extend the life of your sea water cooled components.

 

[CJM]

The "flush" adapter, is "mounted" a the riser, but the hose travels down and is connected somewhere below the engine (I think near the output hose of the raw water pump).. I'll see if I can get a pic tomorrow.

 

[rcknecht]

I put flush connections for a hose before my RW strainers... I would be very careful running water directly in my risers. If the water backs up it could go into the exhaust and hydrolock your engine...

 

[marks737]

I have the same set up. 350 MAG MPI engines. The mercruiser manual tells you how to do it exactly. The sea cocks have to be closed on my engines. Do you have the merc manual?

 

[CJM]

I put flush connections for a hose before my RW strainers... I would be very careful running water directly in my risers. If the water backs up it could go into the exhaust and hydrolock your engine...

They don't go directly in to the risers, the mounts are attached to the risers. The hose meets the system right near the raw water pump (but I can't tell if it's the in or out hose).. (so this way everything gets flushed -- trans cooler, heat exchanger, and eventually out through the exhaust manifolds & risers) but do you close the seacock & do you run the engine? or just let the water pressure do the flush?

 

[rcknecht]

They don't go directly in to the risers, the mounts are attached to the risers. The hose meets the system right near the raw water pump (but I can't tell if it's the in or out hose).. (so this way everything gets flushed

Yes, I close the seacock and run the engines...