Do not Run Honda 135/150 while flushing?

Alyssa Jean

While looking up some other info in the Honda manual I found a warning that said NOT to run the engine while flushing it using the flush hook-up on the engine. Can anyone shed some light one why you shouldn't do this?

Sawdust · Posted: Tue Jan 10, 2006 11:28 am Post subject:

Yep! You will fry the waterpump impeller... so I'm told.

Dusty

flapbreaker · Posted: Tue Jan 10, 2006 12:14 pm Post subject:

My Honda 90 has 2 ways to flush it. One way is with this hose adapter thingy that doesn't flush the whole motor. The other is via "ear muffs". The manual says not to run the motor using the hose adapter method. I think that it's not running water through the important parts. Hope this wasn't too technical for you. Smile

Larry H · Posted: Tue Jan 10, 2006 12:41 pm Post subject:

What Dusty said!

Here's a technical explanation.

The waterpump is located at the top of the gearcase where it bolts onto the tower housing.(leg) The waterpump turns whenever the driveshaft is turning, which is whenever the powerhead is running. The pump impeller is lubricated with water. So is the seal around the driveshaft under the water pump. If the waterpump is dry, ie: not in the water or not having water supplied by flushing muffs, The impeller will heat up from the friction and melt down.

If you 'dry start' an outboard the impeller will 'fry' in 10 to 15 seconds.

Follow the instructions in YOUR owners manual!!

starcrafttom · Posted: Tue Jan 10, 2006 1:16 pm Post subject:

The flushing post was designed to allow the flushing of the motors power head while the motor is in the water. Its for those of us that keep the boat in salt water. You have to tilt the motor up out of the water then flush it with the hose. Ths cleans the salt out of the upper head area that would other wise drain down when you stop the motor. Its not just the salt that does in the motor its the combonation of salt and air. as long as the lower unit is in the water it will be fine. Good thing to do on long trips in the islands on the days you stay in a port.

lloyds · Posted: Tue Jan 10, 2006 4:00 pm Post subject:

This is all great information for new, as well as seasoned four stroke owners. As I am in the "new" category with my recent purchase of a 50hp honda, I am a little concerned that I cannot seem to do a decent flush with the muffs. I have tried them twice, and I never get any water out of the telltale. I then have resorted to the adaptor, but now I hear it might not be the correct method for a motor out of water. I am a little confused, right behind concerned.

UncleRichie · Posted: Tue Jan 10, 2006 6:58 pm Post subject:

hI,
Are you letting it run at a idle? the mits work fine on mine gust put them on and turn on the water and start the engine and let it idle for a few min utes.
Richard

lloyds · Posted: Tue Jan 10, 2006 8:07 pm Post subject:

Yep, I let it idle, but after a while of no water coming out the hole one loses ones' nerve.

rogerbum · Posted: Tue Jan 10, 2006 10:45 pm Post subject:

Papillon · Posted: Tue Jan 10, 2006 11:44 pm Post subject:

Sea Wolf · Posted: Tue Jan 10, 2006 11:52 pm Post subject:

Lots of good advice on flushing engines!

But we still haven't gotten back to David's original question about using the hose flush fitting and running the motor during the flushing:

Does anyone know why the owners manuals for outboard engines with screw threaded hose fittings just below the engine cowlings recommend not running the engine while using the fitting and a freshwater hose?

I can see that there would be a problem if the motor were still in the water, as the pump would still be pushing salt water up into the cooling system, defeating the attempt to get a freshwater rinse.

But wouldn't it be OK to do it if the motor were out of the water with the boat on the trailer? Wouldn't the water from the hose keep the impeller lubricated and cool?

Would the presssure from the hose do any damage to the impeller backing up on it from the outlet side of the pump?

Are there any one-way check valves or pressure relief valves that would stop the hose water from getting back to the impeller?

Can you have too much water pressure in the powerhead?

How big is the inlet in the hose fitting? Is it big enough to allow enough water to go both up and down the water supply passage from the pump, or is it restricted in size to limit the pressure that can be developed inside the powerhead, and hence not able to supply water in both directions?

Of course, if the motor's out of the water with the boat on the trailer, one can easily use the ear muffs which supply fresh water from the intake all the way through, but the above question seems to persist anyway, out of curiosity if nothing else! Joe.

Sawdust · Posted: Wed Jan 11, 2006 12:26 am Post subject:

Joe,

The rep for Honda told me to just flush it with the hose connection and NOT run the motor -- said if I ran the motor with the lower unit out of the water the water pump would get hot and there would be a costly repair and that running the motor was not necessary to flush the engine. I tilt the motor until it is just clear of the water and let it flush away. Of course if you have the lower unit in salt water and try to flush while running the motor you are getting salt right back into the motor.

When on the trailer I just hook up to the fitting and let it flush - don't run the motor. No rabbit ears necessary.

No "why" answers! You can picture this old dude doing a balancing act on the swim step while trying to put on a rabbit ear affair... I LOVE the book way because I keep the boat in the salt water and like keep my motor flushed and free of salt.

Dusty -- see you at the SBS!

Sea Wolf · Posted: Wed Jan 11, 2006 12:39 am Post subject:

Thanks, Dusty!

I'm just trying to get an answer for David and satisfy my own endless curiosity.

"Why" becomes pointless if you simply follow common sense and take the easy way out and follow the rules.

Some of us are just to stubborn about trying to find out why things work the way they do that it get us in a lot of trouble, I guess.

See ya' at the show!!!

Joe.

starcrafttom · Posted: Wed Jan 11, 2006 2:03 am Post subject:

Back tothe muffs for a second. the muffs with the rectangle rubber ears dont work worth a damm. the ones with the round ears work a better. And make sure the water is on all the way.

Question does the water come out the line when you are running the boat in the water? some time the little hose will get clogged. pull it off the engine block and blow it out with a air hose.

lloyds · Posted: Wed Jan 11, 2006 8:57 am Post subject:

My tube is okay, just doesn't flow with the muffs. I might look for some better muffs at the show. I bought the flushing attachment but put it away too good.