Catastrophe impeller meltdown

[elpaso]

-<br /><br />1989 Alpha 1 outdrive - complete unit was replaced with rebuilt outdrive, from local, well <br />known rebuilder, has been in business for 20 years. <br />History - I installed outdrive and new shift cable - with muffs and strong flow of water-<br />ran engine 3 times for 1 minute, setting shift cable, everything appeared normal. Risers<br />were cool.<br /><br />Owner dropped boat in water - reported - within 1/4 mile heat alarm went off - temp. <br />220, and smoke from engine, exhaust hoses are burnt.<br />Impeller housing is melted - also water tube and tube retainer on upper unit.<br />Checked oil cooler - hoses - flow from transom through engine - nothing is plugged.<br />Manifolds - risers and circulating water pump, 6 months old.<br /><br /> Picture follows - I have never seen a melt down like this. <br />The rebuilder replaced unit, with an apology, but could not explain what happened.. <br />Any ideas ?<br />

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[Don S]

Re: Catastrophe impeller meltdown

Plastic bag over the intake would do it. Could also be the owner started the engine without water. <br />Also, is it just my eyes or the camara angle, but is the splines on the shaft bent (Lower Left in the picture.)

 

[elpaso]

Re: Catastrophe impeller meltdown

Splines are good, must be the lighting.<br />I have seen lots of burnt impellers - <br />but not like this?<br />Rebuilder din't even ask, had a new unit loaded up in 10 minutes.<br />Thanks for reply.

 

[Scaaty]

Re: Catastrophe impeller meltdown

YEP! Blame your local beer drinking slob with the plastic bag......I look at my temp every 30 seconds it seems now, after I did the same (only caught it in time), only I don't know if it was a bag or jellyfish. <br /> And those splines do look weird

 

[THE BEEF]

Re: Catastrophe impeller meltdown

Those splines do look strange at the bottom of the cut.

 

[DHPMARINE]

Re: Catastrophe impeller meltdown

Definetely a good example of running without water,either on land or in the water.<br />Best I ever saw was a 70hp johnson that actually rotated the middle cylinder liner.<br /><br />DHP<br />if you let your head list a bit to starboard,those splines look a bit better

 

[ziggy]

Re: Catastrophe impeller meltdown

wow, melted the whole waterpump cover and left the sleeve.... yikes. i thought that i had melted mine pretty good but ya beat me. i had my waterpump cover all blisterd, water tube guide melted into a ball. also i have a question for ya. ya say it was "the unit was replaced". my question is, was the upper replaced too? ya say the water pocket cover was melted too thats why i'm asking. my waterpocket cover was blisterd and the seal was leaking and i had to go to great leangths to get it replaced to seal it. also what about the flappers. wonder if they melted too. mine did. or at the very least they were gone and my guess was from the melt down from an overheat... i agree robby. i look at my temp gauge almost as often as the tach. maybe more. as for why. i don't have the least idea. i figured mine was from running it for the few seconds that i should never do w/o water to it. i'm on my 3rd impeller and am hopefully finally learning to turn the water on 1st. live and learn for me. i agree the splines look bent at the bottom, must be the lighting . also for a rebuilt unit, it looks pretty shiny at the upper lower drive shaft seal. a little wear starting to take place there maybe. and that was deemed ok for a rebuilt? i feel better about mine now if thats the case. i did a speedi-sleeve on my drive shaft as it looked a little worse than yours. cool the rebuilder replaced it w/o questions. that's the kind of stand behind your product service that customers like to see.....

 

[flashback]

Re: Catastrophe impeller meltdown

Hi elpaso, Ive never bought a rebuilt drive so this statement may be dumb, but Ive bought a few engines in my life and usually they are cleaned up before rebuilding and then freshly painted. that drive unit looks like it could have been in the water for quite a while. do they not clean them up when they rebuild them...

 

[elpaso]

Re: Catastrophe impeller meltdown

Flashback -<br />The exterior of the outdrive looked like new when installed. <br />The pump housing, water tube, seal housing, and shaft, that <br />you see have been extremely overheated. Thus- the burnt, dirty appearance.<br />The shaft spline was in perfect shape - that question was asked. <br /><br />I have installed over 100 Alpha Ones over the years, and have <br />never seen a pump melted like this one. Before returning to<br />rebuilder, I stopped at local Merc. dealer ( I know them) and<br />had two of the wrenches look at unit. Both agreed- had never<br />seen one this bad. <br />When I posted picture, I was not looking for the normal - ran it<br />out of the water - plastic bag - classic over heat. But has anyone<br />actually “seen” one this bad ? <br /><br />Thank you for post. Elpaso

 

[mercrewser]

Re: Catastrophe impeller meltdown

I've seen one this bad. Engine ehaust will melt it in no time. He would have had to run it out of water for awhile to melt it like this. Engine under a load with no water to cool exhuast is more likely; plastic bag.

 

[mercrewser]

Re: Catastrophe impeller meltdown

What does the impeller look like? Was it at fault?

 

[trog100]

Re: Catastrophe impeller meltdown

i have always thought of friction heat caused by the impellor running dry as doing the damage.. <br /><br />but mercrewsers "engine under load hot exhaust gases" comment makes such a mess easy to imagine..<br /><br />with no water to cool the exhaust gases and the engine under a heavy load it must get pretty hot in there irrespective of the actual impellor running dry and causing friction heat..<br /><br />the rest of the engine must have gotten pretty hot as well.. exhaust bellows for example..!!<br /><br />trog<br /><br />as for those splines.. nothing wrong with them but it does look like the shaft has been brought to an abrupt halt sometime during its life (rope around prop..??) causing the entire shaft to twist slightly and very nearly shear.. if a drive shaft does ever shear thats the place it would go.. right where it leaves the female splines..

 

[gspig]

Re: Catastrophe impeller meltdown

It is possible that the gasket under the pump housing did not seal. I burned 3 pumps before I found out the gasket under the pump was cavitating once I got on plane. With the muffs on and at displacement speed, the pump was below water, once I was on plane the pump was above water and sucking air. I found the problem by putting the muffs on the lower unit only after I put a new pump housing on.