What does a snapping head bolt sound like?
 

Took the boat out for her maiden voyage of the season today - 1990 sea ray 220 cabin cruiser with 7.4l mercruiser (454 big block Chevy rigged for marine use) and bravo one outdrive. Warning buzzer went off as soon as she fired up - low on gear oil. Topped that off and started right up no problem. Didn't make it out of the harbor before the warning buzzer went off and the temp needle pegged. Immediately shut it down and opened the engine compartment to copious black smoke blowing around the valve covers and 4 or 5 distinct metallic ping noises. After letting it cool off a bit she started back up and we limped back to the ramp and got her on the trailer. Again. More black smoke and a few more pinging noises after shutdown.

I think what happened is that the water pump failed, the block overheated, the heads warped, and the head studs popped. That's the only way I can explain the ping noises, unless that was the sound of the block cracking multiple times but I doubt it.

I was going to pull the water pump and then go from there. Not sure about flushing the cooling system - I will need to read about that. Will start get up again sorry that to assess further damage but I suspect that it won't be pretty.

RIP Blind Squirrel, we loved you dearly.

Btw, does anyone want to buy a boat? She needs a new motor but otherwise she's in fantastic shape!

Sent from my SM-G970U1 using Tapatalk

If the smoke is by your valve covers, chances are that your raw water pump, not your engine water pump, has a destroyed impeller and that’s why it over heated. The small rubber pieces can get in the system and possibly make noise. THere is also metal flappers that keep water from flowing back into the engine that could be making that clatter as there wasn’t any water in them. If you have a closed cooling system (heat exchanger) this is less likely the problem. Could be an easy fix. Good luck!

Yes, it is an open cooling system and I was referring to the sea water pump. I didn't know about those flappers, that would make sense too. I ordered a new impeller last night and will tear it down when I get a bit of time. Planned on back flushing the system too to try to get rid of any pieces lodged downstream. Thanks for the help!

Sent from my SM-G970U1 using Tapatalk

Dana, we were right, it was the sea water impeller. The rest of the pieces were lodged in the oil cooler and came out with back flushing from the thermostat housing side. Amazingly she fired up and ran fine with the garden hose muffs on, topped at 170F with holding 3500rpm for 10 minutes. Looks like the blind squirrel may have some life left in her after all! https://uploads.tapatalk-cdn.com/202...13c41f7b22.jpghttps://uploads.tapatalk-cdn.com/202...17ec227829.jpg

Sent from my SM-G970U1 using Tapatalk

Awesome! Feels good to get all the pieces back. Easy fixes are the best!

It beats the hell out of snapped head bolts!

I thought it interesting that some guys relieve the impeller yearly with winterizing. It never made sense to me why it would be such a high wear item but now I get it. The impeller blades actually bend to conform to the housing. I used the house clamps from my inlet and outlet tubes to deform them enough to get the damn thing in there. Weird design... https://uploads.tapatalk-cdn.com/202...ad57efca6f.jpghttps://uploads.tapatalk-cdn.com/202...4f590d709e.jpg

Sent from my SM-G970U1 using Tapatalk

I change mine every 3 years just to be safe. Way better than a snapped head bolt.

Smart man! I've learned my lesson.

Sent from my SM-G970U1 using Tapatalk