Dry run water pump damage?

[robert graham]

O.K., back from Florida and fogging motor.....forgot to put on muffs ...ran motor dry maybe 15 to 20 seconds for fogging and turned it off....What are odds/chances that I damaged the impeller or other water pump parts?....Should I drop the lower unit to inspect or just install new impeller?.....The water pump is new about 6 months ago....I hate to screw up like this...must be getting old!!!

[robert graham]

Oh, by the way, it's a 1999 C90 Yamaha.....

[boscoe99]

I would think the possibility of doing damage is very small.

I would wait until I next used the motor and simply see how well it pees, and obviously that it does not over heat.

[BQUICK]

I knew a guy that did that with a 60s Johnson 40hp.....he would run it out of gas tilted up! Said it dried the water up, blew it out and kept the salt out. I said it had to be hard on impeller. Said he had been doing that for years....
10yrs later I talked to him and asked if he ever put an impeller in and he said once he looked at it and said he almost put it back in. WTF? But....sprung for a new one. He was an odd one.

[boscoe99]

I had a two stroke 25 HP Mercury purchased in 1981. Those were the days when it was somewhat doubtful if a motor would start when the boat was off the trailer and in the water. I started the motor every time with the water pump being dry. Just let it fire up and quickly turned it off. I got about 15 plus years out of the same impeller, even doing what I did. I sold the motor about 5 years ago. It was still hunky dory at the time. Pissed like the proverbial race horse.

I would do it. I don't recommend that others do it. It might not work for them We all have to learn to be responsible for our own actions.

[panasonic]

My old man had a 40 mariner and use to start it for a few seconds on land at the beginning of each year with no muffs. I would venture to say the impeller was not changed for 15 plus years. It was still soft and the engine peeing fine when I insisted on changing it. He thought it was a waste of money...lol

[walleye1]

And we tell customers to change impeller every three to four years.

[99yam40]

I installed just an impeller when I 1st got my C40, and it failed in less than a year.
lost a couple of vanes, pee stream got weak.
only thing I can think of was I had tilted the motor up while poling across some shallow flats sight fishing for reds and when I get ready to leave that area I fired up the motor for just a second or two(you know when the exhaust is not in the water from the noise) before letting it back down into the water.
may have done that a couple of times.

maybe the impeller was just old sitting on the shelf in stock for a long time, but something caused it to come apart.
I have just bought and installed kits from then on.

I would fire it up on a hose or in a bucket to make sure it pumps and pees OK.I would hate to wait until I was going to use it to find out it may need attention

[TownsendsFJR1300]

I'd lean towards yanking and replacing it.

Too many stories of a vane breaking off and getting stuck in the cooling system...
Housing warp with heat, etc

You've changed it before, it's not difficult, and it's not expensive.

Just not worth wondering if it's good, going to over heat, etc while out on a trip..

IMO, if any doubt, change it.

Just my 2cts

[rodbolt17]

I would lean towards pulling it apart for inspection. takes an hour.
if it fails it takes about 14 hours and a whole bunch of other parts to replace a piston.

[robert graham]

I would lean towards pulling it apart for inspection. takes an hour.
if it fails it takes about 14 hours and a whole bunch of other parts to replace a piston.

For my peace of mind I'll drop it and inspect/replace, as needed....I'll let all you folks know how it looked...just for future information. Man, I hate stuff like this!....guess it's old age or worse!

[zenoahphobic]

Older engines were tougher! I never ran without water but had an impeller last 12 years. These anecdotes show that an impeller can be worn (even from dry running) and still work for years. I suspect that this is because they are effective centrifugal pumps where the impeller doesn't even need to touch the sides.

We are all saying this to make the OP feel better.

But there also seems anecdotal evidence that the impeller becomes toast very quickly out of water. So only the OP knows whether the running was too long: you rely on gut feeling in these cases.

[99yam40]

For my peace of mind I'll drop it and inspect/replace, as needed....I'll let all you folks know how it looked...just for future information. Man, I hate stuff like this!....guess it's old age or worse!

I understand where you are coming from.
forget once is not good, but forgetting several times can be a problem

[robert graham]

Update: I dropped the lower unit and carefully inspected the impeller and it looks pretty much like new.....but there was some heat discoloration on the inside surface of the water pump housing right where it contacts the stainless impeller cup.....so it may have been getting close to melting/doing serious damage. ...So I put it all back together and it's pumping/ peeing like a pro....so I guess I may have dodged a bullet this time around. As mentioned before I only ran the motor for maybe 20 seconds or so,......guess that discoloration on the pump body is nothing to worry about?....or what are your thoughts about just springing for a new pump body just to be totally sure??? Thanks for your thoughts on this....

[walleye1]

I'd run it myself. I would not have dropped the gear case if i did not have a new impeller on hand, they are under $30.00.