New Mercury 20HP system question

[Jimbeau]

Flushing the engine: Why does the manual say to limit this to 3 minutes? I’m assuming it’s because of overheating but why? With water going to the foot it would seem that it’s getting the same amount of cooling as in the lake. The book also says to limit the engine speed to idle. I’m just not understanding the difference mechanically.

Unfortunately I figured this temp issue out the hard way. I hooked up my water hose the old school way with a foot adapter and ran the engine for a while at idle or slightly above just to get fresh gas through the system. I let it run for a bit while doing some other yard chores and sure enough it got too hot! The red light came on and it began running badly. I immediately shut it off when I realized what was happening. Then I read the owner’s manual and realized there’s a time limit and also a dedicated water hose inlet on the side of the engine.
I let it cool and connected the water hose directly to the hose inlet this time. I ran the engine again for about 2 min. It’s seems to run fine now but I’m concerned about possible damage and frustrated with myself for making this mistake. I didn’t think to read the manual just to flush an engine. I’ve owned plenty of outbounds before and have never had a dedicated water hose connection, or an overheating issue with running the motor during flushing.

Thanks upfront and Happy New Year

 

[LDUBS]

What outboard if you don't mind my asking? My Honda outboard has a hose connection for flushing the motor. But, it is not supposed to be used with the motor running.

Sorry, missed that is was a 20hp Merc.

 

[Pappy]

If you are using the ear muffs that are sort of squared off......stop! Those are notorious for driveway overheats.
Purchase the muffs with the totally round seal and use those. Always make sure they have a fairly snug fit against the gearcase.

 

[Jimbeau]

The new Mercury’s have a dedicated water hose inlet on the side. Of course I didn’t know that upfront.

 

[Jimbeau]

Does anyone know if the safety feature cuts off the engine before overheating on the new models? Trying to figure out if I’ve done any damage or does the protection feature help prevent. I know the protection feature does this for other warnings like overspeed.
Also wondering why (even with the dedicated water hose port) Mercury limits it to 3 minutes?
Thanks!

 

[cyclops2]

Those ear muffs are............ONLY.......... for people who stand RIGHT THERE. ALL THE TIME !!!!!!!!!!!
They are great for overheating a motor or cooling pump impellor. If revved up in rpm.

 

[Stand Up]

I use the water muffs for cleaning the cooling route after being in water with lots of algae or other junk. But I only run it for about 1 minute or less and I tend it for the whole minute. If I ever need to run it to do repairs, I'll put it in a barrel of water. But hopefully I'll never have to get right in there and rip it apart.

 

[cyclops2]

I use a 50 gallon drum. Use a clamping lid. Stops Mosquitos & others.