flushing through water tube

[js5278]

I'm having cooling problems with a 1984 40HP Evinrude. I have good flow out the telltale, but I get barely a trickle out the prop hub, and if I run the motor at just above idle for more than 10 minutes, the temperature alarm will go off. I've changed the thermostat, but this didn't correct the problem. I currently have the lower unit off to change the water pump. I'm wondering if I could have some salt blockage in the water channels in the block. Can I safely hook a water hose to my water tube and try to flush the system out? I'd do it, but since the thermostat would be closed, I'm wondering where the water would go out. Maybe the pressure relief valve would take care of this?

 

[jim dozier]

Re: flushing through water tube

I believe you would have to take the thermostat out (or run the engine at operating temp so the thermostat was open) in order to flush the block and cylinder head. If there is much corrosion blockage flushing probably won't do much. I have just recently pulled the heads and exhaust covers on a Suzuki that was overheating and the degree of blockage was such that it required mechanical scraping to remove it. It isn't dried salt that is blocking the passages (if in fact that is the problem) it is aluminum oxide and carbonate (basically aluminum corrosion that is accelerated by saltwater) that is the blockage and this stuff is relatively insoluable in water(and pretty hard stuff). The idea in flushing after use is to prevent the formation of these deposits not to remove them after they have formed. <br /><br />I would remove the thermostat and put the hose in the thermostat fitting and backflush the block and then also do it from the bottom up. Maybe you have some impeller pieces in there. Also use compressed air. <br /><br />Also have you verified that the engine is in fact overheating and not just a bad sensor?<br />Good luck.

 

[jamiei]

Re: flushing through water tube

i read this and was wondering... what can I do to flush out the cooling system on my 69 Merc 500? I'm getting a new impeller and not sure if I need an exhaust seal also.

 

[Walker]

Re: flushing through water tube

I have successfully flushed out a bunch of motors by running them in a barrel filled with a strong vinegar/water or CRL/water solution. I run the motor til it reaches operating temp then shut it down and let it cool. Repeat this process 6 or 7 times a day for 2 days and they have all come out clean.

 

[StAugVol]

Re: flushing through water tube

JimD<br />the hot engine alarm went off on my '97 Evinrude 115 idling to the ramp dock from the trailer. got it home and ran it again on the hose for 20 minutes, measuring the temp on top of the cylinder banks, wasn't hot and no alarm. what's the best way to isolate a sensor problem?<br /><br />Thanks

 

[SCO]

Re: flushing through water tube

StAug, When on a flushette, your water pressure can overcome a defective water pump impeller. You might ought to check that and replace to make sure it is ok. Also, a temporary weed blockage can cause what occured.

 

[Jack Shellac]

Re: flushing through water tube

Salt Away is a good product for flushing out salt deposits. You can get it at most marine stores.

 

[StAugVol]

Re: flushing through water tube

Very interesting, thanks SCO. I'm going to tackle the new impeller, my guess is it's the original one in there. From everything I'm finding the previous owner didn't take very good care of her. Poor girl, I'll get her right again!<br /><br />One of these days maybe I can actually help someone like all of ya'll do...