Merc Cruiser flushing problem

[Dexters dad]

I ran the boat for three hours yesterday evening -- no problems.

This morning when I flushed the engine some problems developed and I would appreciate some input.

First -- the engine is a MercCruiser 4.3 with an Alpha stern drive. I flush with the factory earmuffs and the Salt Away system.

I turned on the rinse water first then started the engine -- I immediately noticed that the water was being evacuated through the engine despite the fact that the engine sat overnight and was at ambient temp. This has never happened before -- usually the engine comes up to temp then the water starts flowing.

After 10 minuets I went to start the Salt Away flush but momentarily stopped the water from flowing by pausing briefly in the off position. (only seconds) When I finally turned the valve to Salt Away the engine had been drained of water and would not flush again despite the fact that water was flowing through the muffs.

At this point the engine temp began to rise past 175 so I shut it down.

I tried to flush again 30 min. later but the water would not flow and the temp began to rise above 175 again -- shut down again.

Thanks for you help with this. Dexter's Dad

 

[Bondo]

Re: Merc Cruiser flushing problem

I turned on the rinse water first then started the engine -- I immediately noticed that the water was being evacuated through the engine despite the fact that the engine sat overnight and was at ambient temp. This has never happened before -- usually the engine comes up to temp then the water starts flowing.

Ayuh,... Normally, unless the motor has been Drained, the water should be flowing, Regardless the motor's temp...

After 10 minuets I went to start the Salt Away flush but momentarily stopped the water from flowing by pausing briefly in the off position. (only seconds) When I finally turned the valve to Salt Away the engine had been drained of water and would not flush again despite the fact that water was flowing through the muffs.

My guess is,... Those few seconds were enough to Smoke the impeller...
Maybe it was already on it's last legs...

 

[Dexters dad]

Re: Merc Cruiser flushing problem

Thanks Bond O

I suspect you're right -- does the thermostat work like a car? that is -- open once the engine comes up to operating temp? I also notice in previous fleshings that the port side is where most of the water exits very little on the starboard side.

Thanks for you help -- Dexter's dad

 

[Bondo]

Re: Merc Cruiser flushing problem

does the thermostat work like a car?

Ayuh,....Sorta,....
When started, it's closed, the raw water by-passes, goin' through the exhaust....
The motor heats the water inside the block to the T-stat rating, then opens....
The heated water is overboarded through the exhaust,+ cold raw water is diverted into the block to start the process all over again...