flushing question

[pat8839]

Hey guys, just wondering how long you flush your engine on the muffs after you use it. I have a 4.3L Mercruiser I/O that I always flush for a few minutes when I get back to house but was wondering how long one is supposed to flush for...


I run in salt water occasionally and brackish the rest of the time

 

[Fireman431]

Re: flushing question

Long enough for the thermostat to open up so fresh water can get through the entire system. 5-10 minutes is usually way more than enough time.

 

[BTMCB]

Re: flushing question

Long enough for the thermostat to open up so fresh water can get through the entire system. 5-10 minutes is usually way more than enough time.

+1 - until T-stat opens. Then, if using a product like "salt away", wait for the foam to start coming out and then shut her down. Leaves a coat of the product on the internals.

 

[pat8839]

Re: flushing question

Forgive my ignorance, but how do you know when the thermostat opens?

 

[Mohawkmtrs]

Re: flushing question

Keep an eye on your temperature guage...when the temp starts rising, the thermostat is opening.

A couple of more minutes and it'll open up completely.

Then you will be at operating temp.

 

[bow wow rider]

Re: flushing question

i always do 10 minutes. the temp gauge hits halfway after about 5 minutes. it's never supposed to go much over half, so i figure at that point, the thermostat is fully open. then another 5 minutes for the full flush. i'm not sure exactly how much water my cooling system holds, but i'd guess it's at least 2 gallons.

 

[veritas honus]

Re: flushing question

Limit the time to around 15 minutes. More than that and you may start doing damage to the water pump. It does depend upon how much water you're getting through the system with the muffs and your garden hose. When the outdrive is submerged, it gets water with little to no air. When you run water through the muffs with a hose, your getting a lot of air which causes partial cavition in the pump. This causes it to run at higher temperatures, and shortens the life of the pump. 15 minutes at a time, though, is generally fine. If a water pump would last 20 years, maybe it will only last 15 or 16 years running on the muffs for 15 minutes a few times per week. If for any reason, you need to run the engine for extended periods of time, such as while doing repairs, then you can submerge the outdrive in a large tub. This is what many marine mechanics do. Anyway, didn't mean to chew your ears off. Hope this helps.

Safe and happy boating always!!!

 

[Fireman431]

Re: flushing question

Just to clarify...Put the muffs on and turn the water on around 1/2-3/4 of the way. You don't need to run the hose wide open.

Start the engine and watch the temp gauge every minute or two. Since you are running cool fresh water, it will take longer for the engine to get to temp. Once the gauge gets near the t-stat temp, the gauge will go down 15 or so degrees.

After 5-7 minutes of running the engine (always at an idle), shut it off. It really only needs to run a couple of minutes to flush dirty or salty water out. You aren't going to sanitize your engine! Think of all of the boats with inboards that moor in salt water. They don't get flushed at all. Ever.