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i just changed the impeller on the sea water pick up on a z222 shabah with a 7.4 merc 1999 model bravo one . Does the system need some kind of reverse flush or is their a collector because the impella was in peices and couldnt locate all the peices thanks luke

I've never heard of anyone doing a reverse flush to get broken bits out... Most likely it travelled through the system and came out the exhaust.

Hello Luke,

As far as I can remember, there isn't any filter or collector on the 7.4 open sea water cooling system so chances are the broken pieces have flushed out or will flush out if they're small enough. The problem I can see is if a piece is stuck to the thermostat.

Have you tested the engine after you changed the impeller? If not, them do so and monitor the temp especially around the exhaust manifolds for at least 10 minutes. This should tell you if there are any blockages.

Or if you’re still concerned, just contact any authorized Mercruiser service center for their advice.

WetWilly

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what was not appropiate in this message mariah man

Quote:

Originally Posted by WetWilly (Post 3991)

thanks mate just one more thing , should i take the thermastat hose off and run the hose threw while the sea water pump is diconected

Hi Luke,

Removing the hoses and trying to back flush with a water hose wouldn't hurt.

If you do remove the hoses, remember to back flush the oil cooler as I believe this is the first unit the waters flows through after leaving the main pump and this is where the missing pieces may be sitting in.

After the cooler, the water then it goes to the thermostat housing where it is diverted to the motor, front water pump and the exhaust manifolds and elbows.

WetWilly

Thanks for your reply wet willy your responce is greatly apreciated . When i perchaced the impeller 4 the sea water pick up the guy said ,make sure you put all the missing peices back together so you know that their is no more peices in the engine.. is that posible ? wouldnt some get flushed out? the guy at the spare parts shop made me paranoid and im hesitant to start it up with out double checking .

Hi Luke,

If the pieces were small then they most likely they went out through the exhaust and assuming the boat was running in the water at the time, you’re unlikely to find all the pieces.

Since you did the impeller change yourself, I'm sure you noticed that the exit opening for the primary pump wasn't very large so the pieces that broke off would have to have been that size or smaller to get through.

For your peace of mind, go ahead and remove the hoses at the Thermostat Housing, Oil Cooler and Front Water pump, try to back flush. Afterwards, with a narrow flashlight, check inside each of them for any signs of the broken pieces. If all looks clean, then I would put it all back together.

If the boat is out of the water, hookup the earmuffs to the outdrive, turn on the water and start up the motor. Let the motor idle until it reaches normal operating temperature, check for leaks and keep monitoring the temp especially around the exhaust manifolds for at least 5 to 10 minutes after that. Should the temperature continue to rise, shut off the motor but let the water continue to run until the motor has cooled down. Otherwise, if everything looks good, then you should be fine for good times out on the water.

WetWilly

your the best wet willy your very helpfull