Hauled boat up on trailer today and ran for a few seconds with the lower unit out of the water. How long does it take to do engine damage or impellor damage while running dry??
Gradyrod
Gradyrod
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Running outboard with no water!
- Thread starter gradyrod
- Start date
cedarholm
Well-Known Member
I don't think a few seconds would hurt.
When was waterpump impeller changed last?
Waterpump rebuild is fairly easy to DIY.
Are you winterizing soon?
When was waterpump impeller changed last?
Waterpump rebuild is fairly easy to DIY.
Are you winterizing soon?
Run dry?
Here is a graphic depiction of what can happen ... although I do not vouch for the authenticity of the purported "torture test."
http://www.brokeboats.com/drypump.html
My personal experience (replacing impellers after one of my own boneheaded "run dry" mistakes) was that no damage was done to the impellers, nor to the plastic impeller housings, which can apparently "melt" from excessive heat build up. That doesn't mean it can't happen of course. I am just the cautious type. Once we tore down the lower unit, it was a "no brainer" to go ahead and replace the impellers, even though the old ones looked good.
I would recommend a practical test. If your cooling water flow appears "as normal" and your engine does not overheat, you're good to go. If, like me, you have cooling water pressure data available (which I added after my bonehead move) it is a simple matter to compare your "before" and "after" pressure readings.
Here is a graphic depiction of what can happen ... although I do not vouch for the authenticity of the purported "torture test."
http://www.brokeboats.com/drypump.html
My personal experience (replacing impellers after one of my own boneheaded "run dry" mistakes) was that no damage was done to the impellers, nor to the plastic impeller housings, which can apparently "melt" from excessive heat build up. That doesn't mean it can't happen of course. I am just the cautious type. Once we tore down the lower unit, it was a "no brainer" to go ahead and replace the impellers, even though the old ones looked good.
I would recommend a practical test. If your cooling water flow appears "as normal" and your engine does not overheat, you're good to go. If, like me, you have cooling water pressure data available (which I added after my bonehead move) it is a simple matter to compare your "before" and "after" pressure readings.
catch22
Well-Known Member
My local Yamaha dealer told me to "never" run the motor without water, (either submerged or on ear muffs). Even if your only doing a compression test, (just cranking). I've heard it from plenty of others too.
You'll also see it stated through-out the owners manual.
You'll also see it stated through-out the owners manual.
CJBROWN
GreatGrady Captain
Great link there Pez.
If they are dry and you run them up, then you have rubber vanes spinning in a stainless cup and it wouldn't take long for heat to build up from friction.
If you just hauled the boat and the pump is wet it's more than likely just fine, especially if it was just a few seconds. If it just came out of the water the pump is full of water, it would take more than a few seconds to dry out and overheat.
I just replaced mine at 300 hours, looked like new. The manual says check them every year, but for the effort to check it everybody just puts the $25 part in. I got a LOT of extra parts I really did not need. The impellor and a gasket was all mine needed, but we threw another $100 worth of parts at it - oh well.
Based on the length of time since it was last done or checked, it may be due anyway. Good DIY guides available if you want to do it. I don't think I would have tackled it without detailed instructions. - with them it was a breeze.
But yes, if it's streaming water (peeing) it's fine.
If they are dry and you run them up, then you have rubber vanes spinning in a stainless cup and it wouldn't take long for heat to build up from friction.
If you just hauled the boat and the pump is wet it's more than likely just fine, especially if it was just a few seconds. If it just came out of the water the pump is full of water, it would take more than a few seconds to dry out and overheat.
I just replaced mine at 300 hours, looked like new. The manual says check them every year, but for the effort to check it everybody just puts the $25 part in. I got a LOT of extra parts I really did not need. The impellor and a gasket was all mine needed, but we threw another $100 worth of parts at it - oh well.
Based on the length of time since it was last done or checked, it may be due anyway. Good DIY guides available if you want to do it. I don't think I would have tackled it without detailed instructions. - with them it was a breeze.
But yes, if it's streaming water (peeing) it's fine.
JUST-IN-TIME
Well-Known Member
If next season, it pees like it did before this incident, I wouldn't bother to change the impeller. I do not change mine on a regular basis and know that there is a lot of disagreement on this topic. My boating is limited to near shore and in bay areas and no sand sucking. If I have an issue, I can get a tow.
Usually the impellers fail slowly. Yes there is a chance of a catastrophic failure but that is a possibility for a new impeller also.
Usually the impellers fail slowly. Yes there is a chance of a catastrophic failure but that is a possibility for a new impeller also.
Why not change them your self. This is not a hard job. I did mine when I first got the boat and had NEVER worked on an outboard in my life. I will admit that I have years of experince working on cars, trucks and small tractors and engines. It only took me about 1.5 hrs on the first one and 45 minutes on the second one. Cost was about $60 per lower unit since I installed the entire water pump kit, not just the impeller.
I'm getting ready to do mine this weekend.
I'm getting ready to do mine this weekend.
hotajax
GreatGrady Captain
Running the Outboard Out of Water
I have a goofball sibling who always starts his engine before the splash. And he wonders why he sits in the repair shop all summer.
I have a goofball sibling who always starts his engine before the splash. And he wonders why he sits in the repair shop all summer.
twin250's
New Member
A couple of seconds is fine. My motors are 20 years old and the water pumps have NEVER been replaced. I always start the motors before they are in the water (only a second or 2). If your not sure on how to do it Have your mechanic do it. There are some folks out here that try and give advise yet they have only had boats for a year or two. I remember where one gentleman took his lower unit to his machanic in a box with all parts in it cause he couldn't get it back together. I have had the oppertunity to watch the repair 3 times on my nhbrs boat, That poor guy is always playing/tinkering but very smart and he struggles. I hope this was some help for you.
JUST-IN-TIME
Well-Known Member
Brad1
Well-Known Member
The best OMC mechanic in this area once told me that it takes about 10 seconds running an impeller dry to begin to cause it damage.
But why take a chance. Just don't run it dry.
I always replace my impellers at the scheduled intervals and the old ones ussually look like new. However, just because an impeller looks like new, doesn't mean it will pump water sufficiently. There can be a fine line between an impeller that provides sufficient water supply and one that doesn't. For example, an impeller that has taken a "set".
As a matter of fact, I just replaced an impeller on an OMC engine that was previously replaced 5 or 6 years ago, but had only been run about 20 hrs since then. But the motor had not been run at all in the past several years. As a result, the impeller took a set. The overheat alarm sounded at slow speed. Replaced the impeller. Sure enough, the old one looked brand new. But due to having taken a set the blades just couldn't provide adequate pressure against the walls of the housing.
An impeller is something you should replace BEFORE it goes bad, not after it goes bad.
But why take a chance. Just don't run it dry.
I always replace my impellers at the scheduled intervals and the old ones ussually look like new. However, just because an impeller looks like new, doesn't mean it will pump water sufficiently. There can be a fine line between an impeller that provides sufficient water supply and one that doesn't. For example, an impeller that has taken a "set".
As a matter of fact, I just replaced an impeller on an OMC engine that was previously replaced 5 or 6 years ago, but had only been run about 20 hrs since then. But the motor had not been run at all in the past several years. As a result, the impeller took a set. The overheat alarm sounded at slow speed. Replaced the impeller. Sure enough, the old one looked brand new. But due to having taken a set the blades just couldn't provide adequate pressure against the walls of the housing.
An impeller is something you should replace BEFORE it goes bad, not after it goes bad.
catch22
Well-Known Member
Brad1 said:The best OMC mechanic in this area once told me that it takes about 10 seconds running an impeller dry to begin to cause it damage.
But why take a chance. Just don't run it dry.
I always replace my impellers at the scheduled intervals and the old ones ussually look like new. However, just because an impeller looks like new, doesn't mean it will pump water sufficiently. There can be a fine line between an impeller that provides sufficient water supply and one that doesn't. For example, an impeller that has taken a "set".
As a matter of fact, I just replaced an impeller on an OMC engine that was previously replaced 5 or 6 years ago, but had only been run about 20 hrs since then. But the motor had not been run at all in the past several years. As a result, the impeller took a set. The overheat alarm sounded at slow speed. Replaced the impeller. Sure enough, the old one looked brand new. But due to having taken a set the blades just couldn't provide adequate pressure against the walls of the housing.
An impeller is something you should replace BEFORE it goes bad, not after it goes bad.
Well said.