Have I Fried My Engine?

[jneely]

While motoring down Meeting House Creek today in our CD 27 I noticed a distinct change in the exhaust noise coming from our Yanmar SB-8 engine. A quick look over the stern revealed that there was no water coming out the exhaust. I shut the engine off and sailed back to the dock. The engine was probably without water for about a minute while running at 2/3 power. Later, in my attempt to diagnose the problem I ran the engine again about three times for about 30 seconds each time with probably 15-20 minutes between runnings. In the end it turned out that the water pump impeller was shot. After replacing the impeller the exhaust spit out its usual amount of water and the engine seemed to run well. I have two questions: First, have I likely done irreparable harm to the engine, and, second, how will I know? Also, other than changing the oil are there any other things that I shoud do to mitigate the effects of this incident.

[seadog6532]

As long as the engine starts easy and you don't see any more smoke than you are used to seeing you probably did not hurt it too bad. How long did you run the motor before you figured out it was not pumping water? Is it raw water cooled or fresh?

[jneely]

Thanks for the quick reply. It was a minute or two before I shut it down. The engine is raw water cooled. When I ran it at more than 2/3 power after replacing the impeller it smoked and spit unburnt fuel into the water. However, the engine did the same thing at this time of year last year. When the boat was hauled last fall the prop was covered with barnacles. This spring with a clean prop there was no discernable fuel in the exhaust even at full power. However, in recent weeks the problem has been creeping back. It may have begun spitting fuel at slightly lower rpms today, but that might be my imagination as I do not have a tach on the engine.

[seadog6532]

I think it will be okay. It will not hurt to clean the prop and see if that helps the spitting problem.

[Neil Gordon]

I had a water pump problem three or four years ago that was pointed out to me by someone on the next dock yelling, "Hey, there's no water coming out of the exhaust!" Despite the lack of flow, I hadn't noticed any problem with the temp guage being other than normal.

The water pump was rebuilt and there was no change in engine performance, noise or whatever from before to after.

[Al Levesque]

I knew of a raw water cooled engine that had cooling water flow problems. The engine would run for 15 minutes with no flow at all and after shutting down and cooling off would run another 15 minutes and repeat ad infinitum. I always shuddered at the thought but once the flow was corrected the engine ran well again.

[Oswego John]

My thoughts are in line with the other respondents. I don't think the engine ran long enough to get superheated.

If your engine started to freeze up (oxymoron ?) from overheating, there is no doubt in my mind that you would have been well aware of it.

If there is any small bit of doubt remaining, it wouldn't be a waste of time for you to recheck the torque ft/lbs on your head bolts, especially if it's an aluminum head.

Otherwise, sail on.
O J

[Lew Gresham]

O J, I would take a look at the engine oil also. If any amount of water gets in his oil, it's going show up. As you know the oil changes color (brownish) if water gets in, and it does not take much. It sounds like that might be the case since the engine is spitting fuel out the exhaust when he first starts her up. A compression test would be a good thing to do.

[rtbates]

I'd think not. My main concern would be why you didn't get an over temp alarm?? Next time you may be forward and not able to hear the exhaust note change.

[Oswego John]

Lew and all,

I agree on all points. You can't be too careful when dealing with an expensive engine that your life might depend on in some future time.

I would have mentioned an oil inspection and change had not the author touched on that point in the original post. But it certainly is important enough to mention a second and third time. Clean oil and fresh filters are the life blood of the engine.

To some people who aren't aware of the fact, motor oil has a distinctively peculiar odor when it has been superheated beyond normal operating temperature. Get rid of it. Flush it out ASAP. Some say that it causes acid buildup.

While checking the torque settings of the head bolts, as Lew mentioned, a compression test would remove any lingering doubts. You certainly want to avoid any head gasket problems and the problems that ensue.

Good luck,
O J

[Joe CD MS 300]

If you haven't changed the oil yet, for $22.50 you can an engine oil analysis performed. The report will give you a clue as to whether there was unusual wear. Follow up reports (after the oil change and some use) may be able to help determine if there was any type of ongoing damage. I have been getting an analysis at the end of every season. The reports are very informative.

http://www.blackstone-labs.com/

[Chris Reinke]

jneely - I would agree with the board that you probably did little or no damage. The one question I had was regarding the "spitting unburnt fuel into the water". Was this under load while the boat was underway or while in neutral at the dock? It is very common for a diesel to exhaust fuel or heavier fumes if run freewheeling at higher RPM's without a load. If this was at the dock, then again, I don't think you have anything to be concerned about.

You ran for such a short duration that the engine temperature never exceeded a safe temperature, nor even got hot enough to activate an alarm. You basically had an air-cooled engine...aka my 1972 VW Beetle, which was subjected to much more abuse then your Yanmar.

[Boyd]

The most likely first victims of an engine running without cooling water is the waterlift muffler and the rubber exhaust hoses. They get hot fast with no cooling water in the system. A couple of minutes is usually not enough time to cause harm. Longer than that and they will start to melt or worse. I agree that the chance of internal engine damage is small.

Boyd
s/v Tern
CD 30 MkII
Fort Lauderdale, Fla.

[Paul D.]

One thing that has not been mentioned yet is to check your old impeller if you still have it. I would check to see if any bits broke off and are not there. Pieces of these get into the motor and exhaust system and can clog things up.

Best of luck,
Paul

[Matt Cawthorne]

Unless you spend a good deal of time warming your engine up, in two minutes you probably did not even have the engine up to normal operating temperature, let alone overheating it. Change your oil, check your head bolt torque, and enjoy your boat.

Matt