Chewed up and spat out

[seafox]

Today I took a mate out for a sail. All good so far. We finished our sail (nice gentle 20 knot Northerly cook strait zepher) and started the motor to turn into the wind and take the sail down. Once the sail was down I noticed that the motor didn't sound right. No Phooof splash sound coming out the exaust. I leant over the side and no gush of water coming out. Checked the temperature and the needle was as far in the red as it could go. Oh ****. I turned the motor off and pulled out some gib as I was heading over the bar and only 200m from the swells crashing on the beach. Then I sailed back into the marina. 4.5knots through the entrance to beat the side on tide, turn towards the club house (into the wind) and luff up and then turn down the finger of my pier (wind beam on again at 20 knots). Roll in the furler about 20metres from my berth and turn into the berth with the wind behind me. Start the motor for 20 seconds as a brake and call the diesel mechanic and change my underpants.
turns out the impeller is shredded. No fins left on it.
The mechanic reckons I got a temporary blockage (plastic bag or something) on the outside of my saildrive. Said this caused the impeller to be dry and shred.
Said the blockage would have fallen off in the marina or when I turned off the motor.

This Volvo D1 30 is 6 months old and has done 30 hours.

Do you guys reckon this is a plausable explaination or do you reckon the impellor was faulty?
Now I know how Captain Cook felt coming into a harbour without a motor!!

[seafox]

Forgot to say, motor and impellor have a 1 year warranty.

[swagman]

The mechanics explanation sounds more likely than a moulding or material fault in the rubber - but well done on getting her back in safely and trusting the underpants did not take too many washes.
JOHN

[seafox]

No my jockeys are very absorbable thankyou. The marina manager came out to my pier. He was very impressed with the berthing!

[seafox]

Actually this is the second time I have had to do this in four years. Beats calling for a tow. Sort of Stealth like.

[Alan Wheeler]

Possible. It is very rare for those impellors to fail so quickly if all is right with everything. So I will give him the benifit of the doubt.
Unfortunatly picking up plastic bags is rather a common occurance.
I guess the engine would have just had a good torsion test of all the bolts. Good thing it didn't do damage.
Mate that is some good sailing skills. I might have to get you on board to show me a thing or two.

[seafox]

I don't think my mate even realised how hairy it was. Paula says you can come next time cause she aint going.

[yotphix]

Like everone says, defective impellers are very rare. Take at look at it if you are skeptical. It should look kind of melted as well as shredded. Also, listen and watch very carefully for the next while to be sure that all of the impeller bits came out. When they are shredded that badly you need to be quite diligent to find them all!

[never monday]

It's quite normal to have that happen when an impeller goes dry. I get 5-6 a year here.

[ssullivan]

Seafox, I've had it happen to me. I had a new impellor (1 month old) when I was doing weekend recreational sailing on a Yanmar. The brand of engine doesn't really have anything to do with it. If you open up the water pump and inspect whatever is left of the impeller, you might find clues as to why it happened. As another poster said - shredded or melted? Obvious mechanical failure? Just check it out.

Also, be careful that pieces didn't make it further downstream into your cooling system. They can lodge down there and cause flow issues.

Always ALWAYS carry a spare impeller and know how to change it underway. This saved my butt as I was heading into the Cape Cod Canal one time a few years back. The impeller shredded up on me (it was only about a month old) and I had to change it while drifting ever closer to the canal entrance, in large powerboat wakes, in the middle of the channel, on a windless day. The canal is a major thruway for commercial traffic as well as recreational boaters. It's got a good 4-5 knot current, so I had to act fast.

But yes... it happens and it happens semi-frequently. Don't worry about an impellor being under warranty. It's a cheap little piece of rubber that you need to know how to change yourself anyway.

[Sunspot Baby]

Cooling water intake through the sail drive is not desirable. Passages are too small and easy to block. I put in through hulls and real sea strainers and my cooling problems went away.

George

[jean1146]

I did fry 2 big outboards with plastic caught in the water intakes.As a rule I replace those once a year good or bad. A temperature alarm is also a good thing.JC.

[ssullivan]

George has a good point. I missed the saildrive part. This is indeed not an idea setup without a proper thru-hull to supply water. You need the thru hull so you can use a proper sea strainer.

[seafox]

the sea water enters through a grate each side of the bottom of the saildrive, travels a short distance to the top of the drive where it goes through a seacock and joins onto 50mm rubber pipe. From there it goes to a salt water strainer (plastic bowl type) and onto impellor.
It just happened that the mech was doing the 1st service yesterday so it happened at the right time. He is dropping off a spare impellor as I usually have one but being a new motor I don't have the spares I usually carry.
He managed to get one fin from the start of the heat exchanger, one above the impellor holder and it looked like the rest were in the hose below. Hopefully that was the lot.
I think I would have less chance of getting plastic in the intake at the bottom of the saildrive than a skin fitting at the bottom of the hull. Plastic usually floats at the top of water and not 4 feet down.
Mech is checking the alarms today. The motor must have to get pretty hot before it goes off, as it never did.
Although the motor got hot, I think I saw what was happening before it got to the point of no return. You could still put your hand on it and it didn't smell too bad or paint bubble or anything.