Engine starts but won't keep running

[mikefossl]

Have a Westerbeke 44a that overheated while heading into harbour. As soon as I noticed, I shut down the engine. At about the same time my wife thought she heard a metallic clunk while below. We sailed in and the next morning I changed the oil and the engine started and warmed up normally. A few days later I decided to replace the coolant but this time a few minutes after starting and before the engine warmed up the rpm started to oscillate and then the engine started to lug. This has happened three times in a row after letting the engine cool down.

Everything I read leads me to partial seizure.

Is an overhaul my only answer?

[Hoofsmit]

Valve guide slipped. Do you have a tinkling sound that wasn't there before?

Is the oil emulsified ? Are you loosening cooling fluid?

[DeepFrz]

If it starts and runs okay for a while I would check other things.

Why did it overheat in the first place?

After changing the oil everything seemed okay so it could well be a different problem.

You haven't given much to go by but after the engine stops will it turn over freely with the starter? If so then look to a fuel delivery problem, perhaps a plugged vent? Engine surging could be a sign of not enough fuel. If not then it sounds like you in big trouble.

[Pblais]

You may have a reduced capacity heat exchanger. You can accumulate deposits that reduce the ability for the exchanger to cool the water. Cooling is about water flow through the heat exchanger. A bad water pump, clogged through hull or a stopped up exchanger would be where I would look. A plugged sea stariner would be the easy solution too.

Personally, I pulled my thermostat since I don't use a engine based hot water heater. In that case you really have no need what so ever for a thermostat. A bad thermostat will cause over heating too. If you removed the thermostat and still had a problem I would bet it's a clogged exchanger. Mine got so bad it would overheat in about 20 minutes. It is odd because before it got bad it was not bad at all but suddenly the exchanger got bad enough to overheat. When we pulled the exchanger most of the tubes were plugged up. I still don't run with a thermostat. It's just something to go bad. The temp gauge does not move much any more.

When you overheat the oil pressure drops as the oil heats up at about 25 psi (mine is normally 50) it gets bad and the temp is pretty high (pegged) and you can warp the head (expensive). A westerbeke will take a lot of abuse but you obviously need to minimize. If you caught the overheating early then you didn't damage the engine.

[boatpoker]

Sounds more like you are sucking air. When you changed the oil did you also change the fuel filter ?

[mikefossl]

The oil and coolant level were fine after the overheat, good water flow out of the exhaust with no smoking. The oil had been changed 100 hrs before.

I can change fuel filters but this seems coincidental with the overheat.

The engine actually seemed to be running fine when I noticed the high temp. I shut things down before the alarm.

No tinkle sounds.

Engine starts normally and initially seems to run fine. After a few minutes a tick develops in the tachometer and then the engine starts to bog. I shut things down at that point.

[DeepFrz]

Will it turn over okay? Did you try adding throttle instead of shutting down? I hate playing 20 questions.

[mikefossl]

The heat exchanger was cleaned and pressure tested 500 hrs ago. The engine starts to lug before it warms up so I'm not sure about heat being the root problem.

[mikefossl]

I've tried to add some throttle when it starts to lug but at that point it doesn't get any better, ie it doesn't smooth out so I shut down.

[Pblais]

I'm not sure about heat being the root problem.

If the heat went away then you would not have a problem.

The impeller would be a good cheap place to check. You can still have water flow with a problem in the exchanger. I sure did. If you have water flow then the heat isn't going away. Adding throttle to an overheating engine isn't the right direction. How high does the temp go? How high does the oil pressure go? How long after you start it does it overheat?

If you don't have a coolant problem and you don't have a water flow or heat exchanger problem you could have a stuck thermostat. It's easy enough to pull it.

[boatpoker]

sucking air, fuel starvation or possibly a bum lift pump would be my guess.

[ShaktisBoy]

Just went through this myself. Symptom sudden rpm drop and no response to throttle movement.. Traced fault to cloged fuel line and weak lift pump. Changed both and problem solved. I also added a see through 5 micron fuel filter in place of the non see through variiety that was previously installed between the fuel tank and lift pump. This helps trouble shoot the fuel delivery system. I should add we Also have a racor fuel water sepperator between the lift pump and primary fuel pump. If you have one as well check while the engine is running for any bubbles that may be being drawn into your fuel system. Hint they can be small and slow to show themselves so be patient. Once i had a similar problem on the genset. While watching the genset run i noticed about ever 30 seconds or so a single bubble would percolate into the racor. After 20 or so minutes went by there was enouh air in the racor to draw into the main fuel system causing it to run rough for a minute or so while the air worked its way through the engine.

Good luck.

[mikefossl]

Turns out I had a faulty oil pressure switch. On the Westerbeke it provides power to the fuel lift pump after the glow plug circuit provides the initial prime.

Thanks for everyone's help. Now I know what fuel starvation sounds like!