engine overheated, now what

[todd d]

3.0 L 140hp gm engine, alpha 1 drive. The water hose detached from the drive and the engine overheated while tubing last weekend. I fixed the water hose when I got home and started the engine. It was a little hard to start, but seems to be running OK. I found pieces of the exhaust flapper in the exhaust port, so I know that needs to be replaced. The engine appeared to be totally dry when I hooked it up to the hose.

What else should I be looking at for damage?

Can I install a temperature alarm on an old (1987) engine? With my attention focused on the kids and the tube, it was too easy to miss the overheating engine.

 

[dwheeler7676]

Re: engine overheated, now what

You didn't say how long you ran it w/o water (but since it runs "OK", we can assume not long). How did you notice this condition?

Of the most obvious (read, serious) damage due to one-time overheating is a warped head and/or blown or leaky head gasket (look for signs of water in engine oil [milky appearance] or water in exhaust [persistant heavy white steam]). This can be confirmed with a compression test of all cylinders, looking for an abnormally low reading on the affected cylinder. A cylinder which begins injesting water will soon 'clean up' nicely and may be identified visually with a scope by its lack of carbon atop the piston.

Yes, you can add *both* a low oil pressure *and* a high water temp alarm to your boat. This involves adding temp switches to existing water and/or oil ports on the thermostat housing and/or block and wiring them to an alarm circuit with a [loud] buzzer in/under/near the dash to alert you of either condition so you can look at your gauges to see which one it is. Mercruiser makes such a kit (consisting I believe of the two switches (similar to sending units for pressure/temp) and an alarm buzzer, ref BoatFix.com, etc.

I'd recommend checking with a local marine mechanic about both these issues for further guidance and/or assurance.

Cheers.

 

[todd d]

Re: engine overheated, now what

I'm not sure how long the engine ran while overheated. We were only on the water for 15 minutes, so I know it was less than that. I had shut off the engine to change riders on the tube. When I started the engine back up, I heard a whinning sound and killed it right away. That's when i looked at the temp gauge. We flagged down another boater who towed us back to the ramp.

I think the whinning noise was the engine water pump spinning in air. How can I tell if this pump was damaged, or does it make sense to replace it to be on the safe side?

I will keep an eye out for milkshake in the oil. Otherwise, I think I caught it in time. I will definately add an alarm over the winter season.

Thanks for the help.

 

[dwheeler7676]

Re: engine overheated, now what

I don't think you would necessarily damage the engine circulation pump (mounted on the front of the engine), but if so it would likely only be the seals or gaskets, which would leak, letting you know in that way. (Note: It has a metal impeller which does not contact anything, unlike the water pump in the lower unit with its rubber impeller - which remained immersed in water while underway.)

Keep your ear tuned for knocking and pinging and continued hard starting, and your eyes peeled for water in oil and/or exhaust. If you are lucky, the temp was not too extreme for too long and everything cooled off evenly, without warping anything. (Immediately shutting it down and letting the engine cool off gradually was the right thing to do, btw.)

Note: If you had severely overheated, you would likely have heard water boiling, or smelled something (smoke/burning smell) right after you shut it down. It doesn't sound like that was the case, so you may have dodged a bullet here. If it runs okay after fixing the water hose and exhaust flappers, you might proceed with caution, taking short runs to see how things go.

As before, do not hesitate to take this information to a local mechanic (or two) and ask them for additional advice (especially wrt to checking head bolt torque, and even the carburetor bolts (gasket), etc. after an overheat condition).

G'Luck!

 

[lakeerieboater26]

Re: engine overheated, now what

if you were to hear some knocking and pinging with a little smoke what kind of damage would I be looking at?