MD2B overheated & stopped

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UserError
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MD2B overheated & stopped

Post by UserError »

Having got the engine running & tested we moved the boat yesterday.

Leaving Fowley Island at 05.00 on a falling tide, we were anxious to get out while there was still water enough.
Unfortunately, what with the early hour, disturbed night before and the anxiety if getting stuck in the mud (again), we forgot that the water inlet cock was closed...until the engine let us know by filling the cabin with smoke and stopping.

We were committed by the tide & decided to sail on. Not a huge problem.

During our trip, I looked under the hatch and saw the exhaust muffler elbow at least had melted. I bodged a fix that would send the water into the trap & some of the smoke & tried the engine (after opening the inlet cock). It started & ran, but when I pushed the throttle, the revs didn't increase.
There were no obvious whooshing/wheezing noises (holes piston/head gasket) but I will go & critically listen in the week.

This is not good and is going to cost, I know.

I'm looking for any experience on getting intimate with this engine - tips, gotchas, leads, suppliers, anything useful. I'm a pretty competent mechanic, just not done much with boat engines.
Many thanks
Jonathan
Centaur Polly B
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Re: MD2B overheated & stopped

Post by dj7613 »

Bet you won't do that again! Make it a routine to check for cooling water every time you start.
David
UserError
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Re: MD2B overheated & stopped

Post by UserError »

Yep. Lesson learned. As first trip after a break of some years, we haven't developed any habits or routines. And this is our first boat with an inboard.
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Re: MD2B overheated & stopped

Post by Hardover »

I feel for you. All too easily done especially so when faced with a first passage. Right now I'm not too familiar with the MD so cant offer any constructive ideas. Hopefully the head isnt warped. My MD17 is fitted with audible alarms for oil pressure and temperature and yours will be too and they should have sounded long before any damage occurred. Once you have the engine fettled you will need to clean all the electrical connections. Disconnect them, rub with emery paper and smear with vaseline. Obviously disconnect the power supply first! The routine for starting mine is, with the ignition switched on, to test the alarms before starting the engine. Once the engine is started the very first step is to check that water is coming out of the exhaust fitting in the stern. You probably know all that anyway. Good luck.
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Re: MD2B overheated & stopped

Post by BrightStar »

If the engine can turn over freely by hand and you can feel the compression strokes and there are no external signs of damage you may well be lucky, so change the exhaust muffler, making sure that all of the melted rubber/plastic has been removed, OPEN the sea cock and try starting, leaving it idle for a minute or two, if no disturbing noises try throttling up first in neutral then in gear.

If it starts ok, without excessive cranking, but won't accelerate it I likely to be restricted exhaust pipe or maybe the air intake, or the throttle cable was damaged - does throttle open fully?

These are very robust engines, I would guess most of the smoke etc came from the melting rubber exhaust bellows.

I wish you luck, worst case of warped heads isn't that expensive to fix.
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Re: MD2B overheated & stopped

Post by Waka Tiki »

Agree fully with Hardover its easily done.

I hang my ignition key on the handle of the water intake so I cant physically start the engine without looking at the water first... how sad am I.

Hope you have got away with it.
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Re: MD2B overheated & stopped

Post by UserError »

BrightStar wrote: Tue Mar 27, 2018 2:22 pm If the engine can turn over freely by hand and you can feel the compression strokes and there are no external signs of damage you may well be lucky, so change the exhaust muffler, making sure that all of the melted rubber/plastic has been removed, OPEN the sea cock and try starting, leaving it idle for a minute or two, if no disturbing noises try throttling up first in neutral then in gear.

If it starts ok, without excessive cranking, but won't accelerate it I likely to be restricted exhaust pipe or maybe the air intake, or the throttle cable was damaged - does throttle open fully?

These are very robust engines, I would guess most of the smoke etc came from the melting rubber exhaust bellows.

I wish you luck, worst case of warped heads isn't that expensive to fix.
Thanks, my big concern is melted pistons. I know what can happen - my desk pen holder is a piston from my Midget, trashed by pre-ignition with Formula Shell back in the day. The smoke was predominantly white diesel smoke and the rubber hoses are fine, just the Vetus waterlock elbow.

I've just won a muffler, so will investigate further when that turns up: The air intakes are normal, the exhaust is "freeflow" shall we say - the Vetus exhaust elbow was so melted it looked like a particularly nasty sneeze - nothing to block the exhaust at all! I'll check the throttle action next time I'm down there.

Clutching at straws, in the absence of any noise on stopping, I'm hoping that there may have been a vapour lock in the HP fuel line due to the heat. Two people who properly know about diesels have mentioned that as a possibility.

Waka Tiki. Re keys on water inlet - That is good plan. Ours is under a quarter berth which will invariably have stuff piled on as it's just inside the companionway. I think I'll try it though. I also want an exhaust alarm - Hardover, we have a temperature guauge, but you have to kneel down to read it so it's not a lot of use. I'm not at all sure there are audible alarms on the Centaur/MD2B - just visuals. May be wrong on that.
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Re: MD2B overheated & stopped

Post by Jolly Roger »

UserError wrote: Wed Mar 28, 2018 10:47 pm I also want an exhaust alarm - Hardover, we have a temperature guauge, but you have to kneel down to read it so it's not a lot of use. I'm not at all sure there are audible alarms on the Centaur/MD2B - just visuals. May be wrong on that.
You could easily rig up a small digital thermometer with the sensor attached to the exhaust. These battery operated (or 12V) thermometers have quite long leads so you can move the control box to somewhere convenient. Cost wise battery ones are about £5 regularly from Aldi and Lidl, so you could easily have several set up.
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Re: MD2B overheated & stopped

Post by BrightStar »

You do not have melted Pistons, if the engine turned over, started and ran there is not likely to be much fundamentally wrong with it.

I would fix the exhaust, check that the oil is ok and give it another go, these old Volvo engines are robust and pretty bombproof

If when you hand crank you can feel each cylinder compression that's good
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Re: MD2B overheated & stopped

Post by Vegable »

As you've run the engine with no coolant water it's odds on that the impellor in the water pump has taken grave exception to spinning without any water and will have shredded itself. I think this will reveal why you've no water flow. I'd also check that you've not got any discarded impellor vanes stuck in the coolant water pipes going out of the pump too which might also be blocking the water flow.
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Re: MD2B overheated & stopped

Post by UserError »

Jolly Roger, thanks. I'm definitely on the lookout for a sensor of some kind. The current guage is almost useless as you can't read it without doubling up or kneeling down. Assuming this guage is just a voltmeter, I had wondered about tapping into its supply and calibrating a simple alarm. I'm currently looking for a schematic for a simple alarm system without or with a temperature value output to run from the existing sensor or strapped to the exhaust.

Brightstar, that is encouraging to hear. When I ran it yesterday, it sounded OK which has to be a good sign. As well as it starting easily & running well. I'll try work out how to feel each cylinder's compression and have a go this weekend.

Having said that, what is "starting easily"? Probably 10-15 seconds of cranking. The engine spins, then starts firing intermittently for a short while until it establishes itself. The starting time has got shorter I'm sure, since I first started it (been started maybe 6 or seven times now). Is that good or bad? - it feels good to me as it starts, but I have got no reference.

Mike, the cause of no flow was me not opening the water cock, so definitely known. I checked the impeller yesterday and it is in one piece. I will get a new one but for testing purposes I used it, after checking the vanes whilst bending them quite harshly in both directions. There was water output in the exhaust, but possibly down on what it ought to be, which is not surprising.

One thing I did note is the topography of the pump cover plate: there is a raised "island" in the centre. Is that meant to be like that or should the plate be flat smooth? I have read that wear on the cover plate actually contributes more to poor efficiency than worn vanes ever do. If it's supposed to be flat, any reason why I can't fettle the other side & flip it over? A Speedseal is on my "would be nice to have" list, but I don't want to get one until I know that the engine is good.

Following on from this, I read on here or the YBW forum but can't find it, a sensible source of knurled stainless screws for the cover. One of mine has gone AWOL. It's either resting on something I can't see or I missed it whilst emptying the bilge and it's at the bottom of the river.

Thanks everyone.
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Re: MD2B overheated & stopped

Post by Jolly Roger »

UserError wrote: Fri Apr 06, 2018 7:49 amHaving said that, what is "starting easily"? Probably 10-15 seconds of cranking. The engine spins, then starts firing intermittently for a short while until it establishes itself. The starting time has got shorter I'm sure, since I first started it (been started maybe 6 or seven times now). Is that good or bad? - it feels good to me as it starts, but I have got no reference.
You cannot compare starting a modern diesel car with an old marine engine. Modern cars have the glow plugs start to heat up as soon as the doors are unlocked. So a marine diesel in cold weather must heat the glow plugs before turning the engine over. By doing this it reduces the power required from the battery as both are power hungry. So to answer your comment, 10 to 15 seconds for a first start is quite normal and as the engine is restarted once warm, the time will reduce.
Roger
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