Impeller Question.

[pissativlypossed]

Bit of a mix up with SWMBO today, I was greasing the shaft bearings and after opening the seacock on starboard engine and engaging gear to turn the shaft, did the same on the port engine, yes you've guessed it! didn't open seacock on that one.

Probably ran for less then 2 minutes before I realised what I (we) had done, I opened the seacock and water flowed immediatly, there was the usual flow and I allowed the temperature to run up to normal, with apparantly no ill effect.
The question is, should I change the impeller? bearing in mind that the water pump on the port engine is a pig to reach and that it was only changed at the last service six months ago.

 

[duncan]

surely theres going to be moisture around for 2 mins - it can't suck though the contents of the strainer against the vacuum for starters?

 

[Kawasaki]

You know You want to.
If You don't and summat happens, You'l be possitively pissed! /forums/images/graemlins/tongue.gif

 

[DavidJ]

I suspect that you have got away with it. If any significant overheating damage to the impellor was done then it would show straightway me thinks.
...just keep an extra eye on the temp guage this year but change it next year.

 

[Malcb]

Personally I would change it. Better to change it when the conditions are good, rather than having to change it when the conditions are poor, and it becomes difficult.

Had a similar problem on my engine. Overheat alarm went off in the lock, managed to moor up outside and stop engine within a few minutes. I suspect a plastic bag had blocked the inlet). Still changed the impellor. I was glad I did as the old one showed some minor signs of cracking at the base of the blades.

 

[longjohnsilver]

Now I'm guessing that you were probably still tied up or just pootling out of the marina so still at low revs, in which case you will almost certainly have got away with it.

A friend of mine a few years ago got down to my boat before me and to be helpful he ran the engine for about 20 minutes to get it warmed up, unfortunately he didn't open the seacock. I thought that would have been the end of the impellor so immediately changed it. The old one looked just as good as the new one! i expected to see it shredded or at least for the blades to be damaged, but they were still in perfect condition!

 

[blueglass]

I had run my engines dry at least 6 times in the French canals with blocked intakes and had no spare impellors so carried on as all seemed OK. Checked impellors and looked fine. Replaced at end of season and they were completely undamaged. I would say you are fine, just take it easy for a while and monitor temp gauges.

 

[DAKA]

Every time you change your impeller there is an air lock and 3-4 mins is not unusual to wait for the water to be sucked up.
Therefore you could change it and still expose your new one to the same treatment.

Nitrite impellers (volvo) will stand a higher temp than Neoprene that last longer at normal running temps.

You should be fine.

That said I would without doubt remove it and inspect it before I went offshore, especially if that side is a pig to get to !
A smear of KY jelly will protect it while the airlock is broken.

 

[pissativlypossed]

Thanks everyone! I think I will try a short run and if ok leave it until the next service.