STEAM from yanmar exhaust?

[Vespucci]

Yanmar 3GM30 exhaust producing copious quantities of steam. The engine runs great, but as it warms up the steam production increases and the water coming out of the exhaust decreases. When cold/idling there is lots of water coming out of the exhaust.

I have:

Checked and rechecked for blockage - none

Checked the exhaust mixing elbow, cleared it

Checked for any blockage in the heat exchanger - it is clear

Checked the raw water impeller - no problems

Spent $800 on mechanics who so far have not produced any helpful insight

This problem came on fairly suddenly, the 3GM30 engine is 13 years old and has worked without problems so far. So the plumbing configuration, which hasn't changed, is okay.

I replaced the impeller and the problem went away, or seemed to. I did a weekend cruise and put 15 hours on the engine (no wind) with no problems, but last night.... The steam is back.

My only thought is that the water pump body itself is worn, and this is causing the impellers to fail prematurely. In this case impeller failure means a very minor, hardly detectable change in dimensions (not a catastrophic disintegration). As the engine heats up, the pump starts to cavitate, flow is reduced and so the heat transfer into the flow restricted salt water side of the heat exchange causes the water to boil.

I'm ordering a completely new pump in the hope that this will solve the problem.

any suggestions?

 

[floating dutchman]

When the engine heats up the thermostat closes forcing the water to circulate threw the engine itself instead of bypassing it.

I'd be looking for a blockage in the engine block itself. I don't know how you would check for that.

 

[Innocent Bystander]

Raw water or fresh water cooling

 

[See Level]

Barnacles in the intake thru hull?

 

[Pertinacious Tom]

Raw water or fresh water cooling

It has a heat exchanger.

Did you actually take the heat exchanger off, or how did you check it?

 

[Vespucci]

The engine is fresh water cooled, so the actual fluid that runs through the engine is a water/antifreeze/coolant mix which is in turn cooled by salt water through a heat exchanger. This was checked, the thermostat inspected and replaced. But if the problem was on this side of the heat exchanger we would see lots of water flow an overheating engine and NO STEAM since there would be no heat transfer into the raw water.

No growth on the outside of the boat, through-hull fitting is clear (boat was inspected by a diver, hoses removed from through hull to visually check the flowrate by letting it flow into the bilge.

The heat exchanger was inspected by taking it apart and visually checking that all the flow passages are clear with no blockage.

The key for me is that replacing the impeller solved the problem for a time, I figure something in the pump (worn surfaces?) is causing the impeller to not mate with the body properly, although on visual inspection there doesn't appear to be any problem, and I've had 3 different mechanics looking at it.

Do these pumps (the outer housing, not just the impeller) simply wear out after a time?

 

[bmiller]

What does a raw water pump cost? Couple hundred bucks? Sounds to me like you've tried everything else likely, and cheap, leaving only the most expensive part.

 

[Jaramaz]

"Do these pumps (the outer housing, not just the impeller) simply wear out after a time?"

Yes, they do, but it usually takes a long time. Sand in the water may accelerate, of course.

Visual inspection often doesn't say very much, as it is difficult to see.

From the symptoms I get the impression that too little water is going through, something is blocking (OK, you have concluded this already). It seems this blocking effect gets worse when motor has been running for some time, got warm.

It could actually be many things blocking, most often it is parts from an impeller. In any case, you should try to check if theere is anything blocking, is it possible for you to put pressure in the reverse way? With eg water, connect a hose to the small water outlet of the heat excehanger and then collect the water in the inlet (on top of the engine front, there is a black rubber hose now).

This you should be rather persistant with ... even if it is boring. Start with low preassure, gradually increase. Not too high preassure.

Have the same engine, 3GM30F, have used this method (used normal fresh tap water, with that preassure).

/J

 

[Bryanjb]

Sometimes The ImPellEr Hub WIll De Bond From The Impeller. It Will Pump Water At Idle But Stops Pumping When You Raise The Rpm. Install A New Impeller Even If The Old One Looks Good. It May bE slipping.

Damn Phone

 

[Jaramaz]

Sometimes The ImPellEr Hub WIll De Bond From The Impeller. It Will Pump Water At Idle But Stops Pumping When You Raise The Rpm. Install A New Impeller Even If The Old One Looks Good. It May bE slipping.

Damn Phone

User claims he did that, the new impeller worked good for a weekend cruise with 15 hours of engine (sounds fun), but then it all returned. From that I conclude that the new impeller gave a higher preassure, which worked for some time, but the impeller + pump is not really designed for such high preassures (?) so after some time (these 15 hours) the impeller started to slip somewhat.

Of course, there could be things blocking at any place along the flow. Could very well be something with the pump.

Easy to test the pump - I assume it is the external one, driven be the belt on what I still call the front of the engine. Remove the pump totally (2 bolts), fasten it somewhere connect hoses to inflow and outflow, put the inflow hose in some water, connet an electrical power drill to the pump, directly on the axis or via a belt whatever you prefer, and then start! To really test, create some resistanse on the outlet using a thumb or something. (OK, you will get wet). All this can be done with the pump still attached top the engine - if you have sufficient access to the pump etc. In fact, one possibility is to just replace the outlet hose with another one (longer, with a free end) the start the engine and see how it works. If you do so, do not forget to close the raw water inlet to the heat exchange, otherwise you may get exhausts out that way,

This exercise can be done at the same time as testing flushing water backwards in raw water system, as I proposed earlier. When doing that engine should be cold, not started for some hours. This as if there are any bits blocking, these can hopefully get away easier with a cold heat exchange. Try to collect the outflowing water, or at least have it through a coarse filter - if you collect any bits in that, you know!

/J

 

[Bryanjb]

Or It De Bonded Again

 

[Pinching]

Above are great suggestions.

IF the pump is OK and IF the exhaust ell is OK and IF the exchanger is OK, it sounds like a supply problem. (as noted by others)

Old hoses can delaminate and collapse which will reduce water flow. You would not see that testing under pressure (free flow into bilge), only under suction.

I'd replace the supply lines from the through hull to the strainer to the raw water pump.

P

 

[redviking]

What does a raw water pump cost? Couple hundred bucks? Sounds to me like you've tried everything else likely, and cheap, leaving only the most expensive part.

Try $500. I had one let go the night before departure. No spare. Deck washdown pump plumbed right in and I ran some wire. Ran 14 hours straight. No problems. Why not have electric impeller pumps?

 

[Innocent Bystander]

What does a raw water pump cost? Couple hundred bucks? Sounds to me like you've tried everything else likely, and cheap, leaving only the most expensive part.

Try $500. I had one let go the night before departure. No spare. Deck washdown pump plumbed right in and I ran some wire. Ran 14 hours straight. No problems. Why not have electric impeller pumps?

Diesels run without electricity. Why have a critical system dependent on it?

 

[floating dutchman]

What does a raw water pump cost? Couple hundred bucks? Sounds to me like you've tried everything else likely, and cheap, leaving only the most expensive part.

Try $500. I had one let go the night before departure. No spare. Deck washdown pump plumbed right in and I ran some wire. Ran 14 hours straight. No problems. Why not have electric impeller pumps?

Diesels run without electricity. Why have a critical system dependent on it?

And it gets difficult ensuring that the water pump can't run when the engine is not running etc.

 

[JBE]

Two relatively recent incidents amongst my sailing friends. One had a shellfish grow in the supply line around the through hull/ seacock. It let water through at idle but moved and closed off most of the water as revs increased.

The second one sucked a mangrove seed which made it past the seacock to the elbow right in front of the strainer and did exactly the same thing. Sat there like a tennis ball in a gutter downpipe. let slow water through and closed off flow when under pressure.

Both were concealed , both let lots of water through when the hoses were disconnected up stream. or should that be downstream, you know what I mean.

 

[redviking]

Diesels run without electricity. Why have a critical system dependent on it?

And it gets difficult ensuring that the water pump can't run when the engine is not running etc.

Oh geez, I thought this was the cruisers forum. My bad. A well found cruising vessel will have at least one high output alternator, or as I do two. Also, a well found cruiser will have a emergency fuse block and a spare switch. Turn engine off, turn saltwater pump off. Turn engine on, turn pump on, check for wawa... NOW, for those of you who wish to be schooled by my accidental discovery, a couple Y valves and you could have the best of both worlds. A traditional impeller pump, AND, for that "O shit" moment when the belt or impeller goes mid channel with 25 on the nose and a Constricted By Draft situation, flip your Y valves and turn on your electric pump and keep going... <_<

 

[Pertinacious Tom]

I'm a fan of the Department of Redundancy Department.

I'm also suspicious of seldom-used electrical appliances in salt water. How often do you test that pump, RV?

 

[redviking]

I'm a fan of the Department of Redundancy Department.

I'm also suspicious of seldom-used electrical appliances in salt water. How often do you test that pump, RV?

Since I am the first person I know of to have ever played with such a notion, frequently. That been said, this was my back up pump for the deck washdown which cleans the chain as it comes up. That pump hasn't failed in the six years I've owned this vessel.