Home   |  Message Board   |  Information   |  Classifieds   |  Features   |  Video  |  Boat Reviews  |  Boat DIY
Dry Run a motor - Page 3 - Walleye Message Central
Walleye Message Central

Go Back   Walleye Message Central > Boats, Motors, Electronics and Trailers > Motors and Props

Reply
 
Thread Tools Display Modes
  #21  
Old 12-10-2019, 08:34 AM
Waxy Waxy is offline
Wallhanger
 
Join Date: Sep 2007
Location: Calgary AB Canada
Posts: 2,361
Default

Quote:
Originally Posted by jdavis View Post
How could dry starting your motor for less than 10 seconds cause a problem? Is the thinking here that it might overheat in that short amount of time? If your impeller froze would it not take the same amount of time for it to unfreeze once in the water, possibly running your motor without cooling for the same amount of time?
My guess is that's the concern, IMHO, it's completely overblown.

In cold conditions, with water already in the system, the chances of overheating or causing wear on the impeller in 5, or even 10, seconds is essentially zero. Impellers are tough, it's gonna take a lot more than that to cause them to heat up to the point of damaging them. IMHO, the risk of that damage vs damage due to start up with a frozen impeller is well worth it.

Middle of summer, motor hasn't been in the water in two weeks and completely dry, yeah, then I wouldn't want to run it for 5-10 seconds, there's a much higher chance of causing some wear.

Waxy
Reply With Quote
Sponsored Links
Advertisement
 
  #22  
Old 12-10-2019, 10:48 AM
jdavis's Avatar
jdavis jdavis is offline
Slot Fish
 
Join Date: Jun 2014
Location: Denver
Posts: 112
Default

Quote:
Originally Posted by guest2340 View Post
Unwanted wear on your impeller ovee time.
Being the motor was just pulled out of the water and everything is still wet seems unlikely to cause much extra wear in 5 seconds.


Thanks Waxy for the context. Not starting the motor after it has been setting and dry makes total sense to me.

Last edited by jdavis; 12-10-2019 at 10:51 AM.
Reply With Quote
  #23  
Old 12-10-2019, 11:52 AM
Kevin23 Kevin23 is offline
Wallhanger
 
Join Date: Dec 2014
Posts: 1,801
Default

Also remember that water is not a lubricant. So running your impeller in the water vs out is really no difference. Cooling is the issue, as the impeller runs against the side of the housing it builds heat and water cools it. The impeller and housing is still wet, that is literally the reason why we dry fire it... To get the rest of the water to move and drain out of the system quickly before it freezes. Motor starting vs pulling the kill switch does the same thing, i just prefer to not annoy everyone in the lot with the BEEP BEEP BEEP BEEP of trying to start it with the kill cord pulled. No possible way your motor is over heating in freezing temps being run without water for 5, 10, 30 seconds and it spits the water out of the exhaust too (not that it matters). Not even being already warm from the run back to the ramp will it overheat.

Like i said, I've done it for a couple years now with a new motor and the dealer mechanic said the impeller looked brand new.
Reply With Quote
Sponsored Links
Advertisement
 
  #24  
Old 12-10-2019, 12:53 PM
Waxy Waxy is offline
Wallhanger
 
Join Date: Sep 2007
Location: Calgary AB Canada
Posts: 2,361
Default

Quote:
Originally Posted by Kevin23 View Post
Also remember that water is not a lubricant. So running your impeller in the water vs out is really no difference. Cooling is the issue, as the impeller runs against the side of the housing it builds heat and water cools it.
I'm not sure that's entirely true, but I do agree that the ability of the water to conduct heat and cool the impeller is an important factor.

The water does act as a lubricant, albeit not a great one. Running a dry rubber impeller against a metal surface will create a lot more friction (heat) than running it with even a small amount of water present. It's no different than tires on a road really, decreased traction on wet pavement is the same effect.

Waxy
Reply With Quote
  #25  
Old 12-11-2019, 07:38 AM
Marty59 Marty59 is offline
Wallhanger
 
Join Date: Jul 2012
Location: Michigan
Posts: 1,786
Default

Quote:
Originally Posted by Waxy View Post
I'm not sure that's entirely true, but I do agree that the ability of the water to conduct heat and cool the impeller is an important factor.

The water does act as a lubricant, albeit not a great one. Running a dry rubber impeller against a metal surface will create a lot more friction (heat) than running it with even a small amount of water present. It's no different than tires on a road really, decreased traction on wet pavement is the same effect.

Waxy

The real question is how much additional wear on the impeller are you introducing while running it dry. Obviously, that will depend on how many times you spin (revolutions of) the dry impeller each launch times the number of launches/season you actually do this. If you are trying to get maximum life out of your impeller then this is not a wise strategy to dry spin. If you change your impeller and have life left on it, then you did no harm. I have never dry spun my impeller and change it at about 150 hours/6 years which ever comes first. There has always been a margin of safety remaining in my impeller's life.

Marty
Reply With Quote
  #26  
Old 12-11-2019, 09:53 AM
Kevin23 Kevin23 is offline
Wallhanger
 
Join Date: Dec 2014
Posts: 1,801
Default

4 words if you think water is a lubricant. Sex in the shower.
Reply With Quote
  #27  
Old 12-11-2019, 11:28 AM
Waxy Waxy is offline
Wallhanger
 
Join Date: Sep 2007
Location: Calgary AB Canada
Posts: 2,361
Default

Quote:
Originally Posted by Kevin23 View Post
4 words if you think water is a lubricant. Sex in the shower.
Seriously?

Waxy
Reply With Quote
  #28  
Old 12-11-2019, 01:16 PM
DW DW is offline
Wallhanger
 
Join Date: Jan 2004
Posts: 1,904
Default

Quote:
Originally Posted by Waxy View Post
I'm not sure that's entirely true, but I do agree that the ability of the water to conduct heat and cool the impeller is an important factor.

The water does act as a lubricant, albeit not a great one. Running a dry rubber impeller against a metal surface will create a lot more friction (heat) than running it with even a small amount of water present. It's no different than tires on a road really, decreased traction on wet pavement is the same effect.

Waxy
I concur. Running the outboard 10 seconds after removing from the water will not cause wear. Not only does water act like a lubricant, but it would have to boil off before the impeller rubber can overheat, smoke and cause damage. With a dry pump housing it may only take seconds of run time to overheat the rubber.
Reply With Quote
  #29  
Old 12-12-2019, 11:58 AM
TomP.'s Avatar
TomP. TomP. is offline
Wallhanger
 
Join Date: Mar 2007
Location: .
Posts: 2,151
Default

Do you really think that by starting the motor to blow out the water is really happening ( it is NOT an air compressor ) what about the water left in the tubes running up to the block you do not think this water trickles down into the water pump. The system will never be dry there will always be some water going back down into the lower block and water pump just not enough to hurt anything. I would bet you dollars to donuts that if you would pull off your lower unit after you self drained or fired the motor there will be some ice in the impeller. The motors are designed to self drain.
Reply With Quote
  #30  
Old 12-12-2019, 06:10 PM
tonto tonto is offline
Minnow
 
Join Date: Sep 2009
Posts: 72
Default

We run outboards in the middle of winter. I have seen guys not turn there motors over and have had them freeze up the next day and won’t pump water. My dad built outboards for over 35 years. He always fires up the motor for a few seconds. He is so knowledgeable on some models he can tell you were every bolt goes.
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off

Forum Jump


All times are GMT -6. The time now is 05:38 AM.


Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.