What happened to my water pump?

[Nomo]

2008 Mercruiser 4.3 TKS. I was cruising at wide open throttle for about 10 minutes, then I heard a grind and smelled the coolant. Immediately shut engine down, the engine temp was spiked at 250. I opened the motor cover and saw that the pump shaft and pulley were laying in the bottom of the bilge, along with the engine belt. When I turned the ignition switch off the engine dieseled (sp?) for a long time. Everything I tried to stop it failed until it just finally quit on its own. I'd sure appreciate some guidance on figuring out what happened and assessing the damage to the engine. Thanks for any input.

 

[Bt Doctur]

A severe overheat most likely took out the head gaskets and caused a hydro-lock condition.
1 remove all the spark plugs and crank engine over to remove any water in the cylinders
2 If water is found ,spray fogging fluid heavily into each cylinder
3 remove heads as soon as possible , more than 24 hours with salt water and the motor is done.

 

[Grub54891]

Btdoctor is right. But I think I would put the plugs back in after the fogging and cranking. At least start it for about a minute and pull the plugs again and refog. I think that will clear out the manifolds a bit and help with any further damage to the valves and cylinders.

 

[Grub54891]

As far as the pump, I'd assume its one of them freshwater pump/fuel pump combo units? If so,I don't like them much. I've seen a few failures on them,not as bad as your's but close. There is an oil resavore in them that most do not know about. It should be drained and re-filled every season.

 

[coolbri70]

the waterpump failed and it got so hot that the fuel was running off the compressed fuel and red hot engine cylinders. run a compression test to assess the damage, if you get good compression, replace the pump and run it, if low compression, pull the heads look for blown gasket, warpage, cracks etc.

 

[thumpar]

Just to add to the others, there should have been an alarm when you got close to 200*. Check that while you are fixing stuff.

 

[Nomo]

I don't know why the pictures didn't show up, but I'll try again to send the pump and shaft picture.

 

[ktbarrentine]

Photo posting is not working yet.... Need to go to a site like photobucket-dot-com and setup an account, upload photos there, then copy/paste the img link to your posts. So far it is the bast way I have found.

 

[Fun Times]

Sounds like you have a closed cooling system since you smelled coolant and had a seawater pump?

Being you have a 4.3l V6, do you have a bravo or alpha stern drive?

The dieseling would have most likely been due the heat is all. If you have full closed cooling vs half closed cooling (exhaust manifolds with coolant = full) then you may have avoided getting water back down into the engine cylinders during the dieseling but you'll still want to pull the spark plugs and check for liquid and do an cylinder compression test so you know the status of the engine.

Unfortunately there are many of the same stories online about the seawater pump of your era coming apart like yours just did. The first link below is the best online topic with photos that I know of. You may want to look into the Hardin Marine stainless steel seawater pump now that it's time. Better pump for less $$$.

http://www.smwebhead.com/phpBB3/viewtopic.php?p=60431#p60431

Others have mentioned avoiding major engine damage after this event. Hope your floating in the same boat, good luck.
http://clubsearay.com/showthread.php/49284-Raw-water-pump-pulley-came-off-350mag?p=552636#post552636

 

[Eric 3.7LX Alpha 1]

To add a picture to your message don't use the camera button on the left.... use the A button on the right side, then click on the 3rd option on the right says "image".

 

[Nomo]

Thanks for the help. Fun Times, the links you gave were absolutely spot on to my issue. Yes, I have a closed cooling system with an Alpha One drive and sea water for the engine comes through the hull. I found no obstructions in the pickup grate under the boat, leading me to think the pump just failed by its design. I slipped the shaft back into the pump and tried turning by hand but it is seized. Taking plugs out today.

 

[Nomo]

Pulled the plugs today and everything was bone dry, plugs looked almost new. Dry compression test was 165-170 on all six cylinders. Ordered the Hardin Marine water pump. I can still smell coolant in the engine area since it overheated, but nothing is leaking out anywhere. Only thing I can think of is the smell is coming out of the coolant reservoir overflow. If I've done all the necessary steps it's going back into the water. This engine has less than 300 hours. Mercruiser owners beware!!!