Water Pump Failure...?

[pubnicobob]

1980 - 80 HP Mercury. Running along today at about 4200 RPM and heard rattley sound from motor. Immediately looked back and saw that there was no cooling water stream. Shut down engine and got a tow back home. Motor rolls over as fast as always, so not seized. Questions are...
(1) do pump impellers just suddenly quit, or could there be another problem with the cooling (I was in clear water - no grass)...and (2) is it likely there was any damage to the engine from this incident? Thanks!!

 

[emckelvy]

Re: Water Pump Failure...?

(1) Sudden failure is possible, you never know what you're gonna encounter running in the water, you could have had a plastic bag wrap itself around the intakes long enough to fry the pump, no telling. Or perhaps the impeller was old and cracked a few blades.

(2) Since you caught it before it seized in a cloud of steam, you may have saved it. You might want to take a compression check to see if there's any issues, then periodically check to make sure compression isn't degrading.

Be sure to check the integrity of the impeller key and driveshaft flat where the key sits, I've had failures there which caused the driveshaft to spin in a perfectly good impeller and 'smoke' the powerhead. Any damage severe enough to do that will be obvious.

HTH..........ed

 

[pubnicobob]

Re: Water Pump Failure...?

emckelvy....thanks!! Sounds like I might have been lucky. I've never done a compression check on an outboard, but I have a gauge. Do I just take each plug out individually and check while cranking with the starter (like my old Plymouth 225)? What numbers are good, and how much variation isn't good? Thanks again!!!!

 

[Chris1956]

Re: Water Pump Failure...?

The best way to take a compression check is to remove all spark plugs, and open throttle. Now with ign key off, jumper the starter solenoid while holding the gauge in the top plug hole. Let her crank until the gauges maxes it's reading. Write it down, and repeat with the balance of the cylinders.

Compression should be 100+PSI and within 15% or so. A bad cylinder will normally show as zero or just a few PSI, so you will know it.

 

[pubnicobob]

Re: Water Pump Failure...?

Thanks for all the good words so far. Here's the latest. Put in a new impeller. The old one had 3 broken "fins" with one missing altogether. Took out the plugs to do a compression check. The bottom 3 plugs all looked clean as normal. The top plug was coated with a fine grey material which I had to scrape off. Could this be material from the cylinder walls? Compression on the top cylinder is 135, with the other 3 being about 150. Started the engine and it seemed to run like always with the cups on it. Took that top plug back out after running it about 5 minutes, and there was no sign of any more "grey matter". Question is...now what? Should I use the boat and see what happens, or is there something that should be/could be done to that top cylinder? Also....should I be worried about the missing fin from the old impeller? Water spits out the hole like before, with the cups on it. Thanks again!!

 

[jmburock]

Re: Water Pump Failure...?

One of the fins of the impeller is more than likely still somewhere in your cooling system. Sometimes they end up in the area of the water jacket or exhaust plate. Keep watching your pee flow to see if it stops up again. There are either pieces of the fin or a whole fin still in there from what you told us.

 

[pubnicobob]

Re: Water Pump Failure...?

Thanks Jm. What about the top cylinder? Is it okay to use the boat...and see what happens?

 

[jmburock]

Re: Water Pump Failure...?

Top cylinder is only off by 10% (150-135/ 150), so probably wouldn't worry about it, although you may want to try Sea Foam to see if you can get that number up. Its not related to your Water pump issue.

 

[pubnicobob]

Re: Water Pump Failure...?

What about the grey flecks on the spark plug?

 

[Chris1956]

Re: Water Pump Failure...?

Grey flakes on the plug are bad. Thy will be caused by lean running, overheating or over advanced timing. Igf you do not fix it, your motor will seize.

Therefore, I would clean and rebuild the carbs, and do the link and synch.

 

[pubnicobob]

Re: Water Pump Failure...?

???

 

[emckelvy]

Re: Water Pump Failure...?

If you didn't have the flecks of aluminum on #1 plug before the overheating incident (and it's not likely you did), they're from the top of the piston being fried due to loss of cooling.

#1 will pretty much always suffer the worst damage since heat rises. It's very likely that the piston rings/ring lands were damaged.

15 psi drop from the other cylinders in a Merc is NOT a good thing. I'd take it out and run it one time with a batch of Seafoam in it, as suggested.

If the compression readings don't come up into a normal range (ideally, 5 psi or less difference, 10 psi at the most), the powerhead needs to come apart for inspection of damage.

One less-intrusive thing you can do prior to pulling the powerhead, is to remove the transfer port cover (intake side) - the upper one. It'll allow you to look directly into the intake ports of #1 and, with the piston down, you'll be able to see across to the exhaust side of the cylinder. Check for signs of scuffing/scoring.

If you catch a problem like this early, you may be able to get by with just a basic rebuild including an overbore on #1. If you let it go, it'll only get worse, and has the potential to ruin the rest of the internals as worn metal bits circulate throughout.

HTH & keep us posted...........ed

 

[pubnicobob]

Re: Water Pump Failure...?

emc....thanks!! What does the Seafoam do...and where do I put it?

 

[pubnicobob]

Re: Water Pump Failure...?

What does the seafoam do...and where is it put in?

 

[emckelvy]

Re: Water Pump Failure...?

Seafoam is an excellent decarbonizing additive, it'll clean any carbon deposits which may be causing piston rings to stick.

Sticky rings don't spring in-and-out on the piston like they're supposed to. This will eventually cause cylinder scuffing/scoring and loss of compression.

Check out this FAQ for more details:

http://forums.iboats.com/showthread.php?t=158076&highlight=seafoam