whet through a sand bar and clogged/ruined water pump/thermostats.---1990 merc v-200

danamul1977

Petty Officer 2nd Class
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Nov 15, 2012
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148
I went through a shallow spot after launching on a new lake and very soon after that overheated. The Tell Tale was pretty much gone. Im just looking for some advice on what steps to take to Flush the system (if needed). Im thinking it could of clogged/runed either the water pump or the T-stats. Im going to look at it tomorrow, and im wondering if I should pull/inspect the t-stats for sand, and then just run it on muffs (without the t-stats) to see if I get a stream. Im planning on replacing the water pump/housing anyway, but I was thinking I should backflush it somehow. I cant think how I would do that though, only way I can think of is going through the t-stat housing on both sides. I have a 1990 v-200 mercury. Any advice would be helpful, or im just gonna have at it tomorrow.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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Jul 23, 2011
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47,306
Im guessing you plugged the intake, which lead to destroying the pump.

I would drop the lower, replace the whole pump, rig up a hose to the supply tube to the power head and flush out the block. then re-install the lower
 

Sea Rider

Supreme Mariner
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Sep 20, 2008
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If you drop leg and connect a water hosse to lower water tube will flush the whole crankcase except heads due to thermos being closed, unless they open up with high water pressure and wash both heads if suspecting sand is deposited along water passages. Could remove both thermos, put both lids back on and flush with water hose attached on lower water tube for some minutes.

This high water flushing procedure will remove small deposits, debris, whatever inside all water passages. Take advantage to check thermos cond, if too rusted, buy 2 new thermos and gaskets, with new water pump, engine will cool much better.

Happy Boating
 

Barramundi NQ

Petty Officer 1st Class
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Jul 3, 2014
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342
Good advice, I would automatically replace the thermostats at this point though. remember to grease the bolts you pull out so if you ever need to remove again they wont seize. New impeller kit and remove the thermostats to flush down from the top of the block to clean out all the sand with the engine cold. Install new impeller kit and run the muffs or drum is even better. Start the engine without the thermostats in but the housing hand tight. Check drum for sand coming out. If all good shut down engine and install the new thermostats and run the engine on muffs this time. No overheating alarms???? go out and give it a real test on the water.
Cheers
 

Sea Rider

Supreme Mariner
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Sep 20, 2008
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Unless that engine has a built in port to flush with hose do it that way. If not it's much better to flush high water pressure from lower tube water intake upwards with thermos removed and lids closed, put a barrel under middle leg so not to wet floor. Constant house pressure flushes much better than impeller flushing specially while flushing at idle/fast idle speed. It's a pressure issue. Put back or replace old thermos and gaskets, put lower unit back on and voila, it's a one time job straight to water diversion.

Happy Boating
 

danamul1977

Petty Officer 2nd Class
Joined
Nov 15, 2012
Messages
148
Ok, good advice. What im understanding is, I should drop the lower unit and probably tape the garden hose tight to the water inlet to the block then flush with t-stats out. Then try to flush some sand out of lower unit. Then replace water pump and run with T-stats out for awhile, replace t-stats and test again. Because yes I dont have a port to flush with hose. Thx you guys ill give that a shot.
 

Sea Rider

Supreme Mariner
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Sep 20, 2008
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12,345
-Drop lower unit.
-Connect hose to lower water tube, make a tight fit hose onto water tube.
-Remove thermos, bolt back their respective lids.
-Flush engine for at least 5 minutes with hose.
-Install new thermos and gaskets.
-Wash out lower unit water screens with hose.
-Replace impeller or complete water pump if needed.
-Make sure pipe engages water grommet when pulling leg up.
-Bolt back lower unit.
-Go for a water spin.

No need to flush with muffs/barrel once LU is bolted back, you have cleaned already all water passages and LU screens.

Happy Boating
 
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