Lehman 225 overheating...

Hey guys. We’ve out about 20 hours on the boat since we got her a couple of months ago. On our last trip towards the end of a 5 hour day, we decided to push the power to 1900 RPM or so for a bit. After about 15 minutes or so the starboard engine alarmed, water temp was 200. Port engine was still 175 or so. We throttled both back to 1500 RPM and the temps returned to normal. We anchored for the night and I decided to deal with it the next day if we still had a problem. Well sure enough, once under way the following day, the starboard engine alarmed even though we never got over 1600. We dropped the anchor and cleaned the strainer, which was pretty full. It didn’t seem to make a difference as it alarmed again in just a few minutes. We shut it down and continued on one engine. I thought for sure it was the impeller. I couldn’t track one down so we just continued the rest of the 2 day trip on the port engine, firing the starboard engine just for docking. Once at the new marina, I pulled the cover off the impeller and to it looks brand new. So that ain’t it. The strainer is clean I have water flow out of the exhaust, just not as much as there usually is. Being that this came on so suddenly, I would think there’s a blockage somewhere. But how could anything get past the strainer?

I’m headed to the boat early next week, if anyone has any experience with this and has any tips or tricks to help me figure this out, I’d really appreciate it.

Thanks
Steve

If this were mine I would take all the heat exchangers off and inspect/clean them. Esp since this is a new to you boat and you don't know what condition they are in.
I would do that to both engines.
Also evaluate the condition of all the hoses.
Good luck.

jleonard said:

If this were mine I would take all the heat exchangers off and inspect/clean them. Esp since this is a new to you boat and you don't know what condition they are in.
I would do that to both engines.
Also evaluate the condition of all the hoses.
Good luck.

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How big of a job is that?

Coolant level ok?

You really can't tell impeller condition by just pulling cover. Bad vanes are hard to see. Pull it out to inspect.

Also, take engines up to rpm where the trouble one is just on the verge of getting hot. Go in the ER and check temp of exhaust tubing or mufflers well downstream of engine. If one is hotter than the other, you have low sea water flow for any number of reasons. If both mufflers are same temp, sea flow is the same and the problem is on the coolant side.

Ski in NC said:

Coolant level ok?

You really can't tell impeller condition by just pulling cover. Bad vanes are hard to see. Pull it out to inspect.

Also, take engines up to rpm where the trouble one is just on the verge of getting hot. Go in the ER and check temp of exhaust tubing or mufflers well downstream of engine. If one is hotter than the other, you have low sea water flow for any number of reasons. If both mufflers are same temp, sea flow is the same and the problem is on the coolant side.

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Coolant levels are good. I know it’s a sea water problem because of the reduced sea water out the exhaust.

I’ve been watching videos of cleaning heat exchangers, doesn’t seem too bad. How long does it usually take to clean a heat exchanger?

I think the 225 is different from the more common 120 and 135. There is the aftercooler too and that can be clogged, restricting flow. And that aftercooler can be real bugger. Take it apart and corrosion issues can prevent it going back together without leaks.

I think the sea water flow path goes through four coolers: Aftercooler, gear oil cooler, engine oil cooler and coolant heat exchanger. Any or all can restrict flow. Start with the easiest first. Can also pull hoses and look into inlet side for clogging. Small coolers can clog faster than the big ones.

But start with the impeller first.

I’ll change the impeller anyway. I thought missing vanes were the only thing it could be. Either they are there or they aren’t.

Ski in NC said:

Coolant level ok?

You really can't tell impeller condition by just pulling cover. Bad vanes are hard to see. Pull it out to inspect.

Also, take engines up to rpm where the trouble one is just on the verge of getting hot. Go in the ER and check temp of exhaust tubing or mufflers well downstream of engine. If one is hotter than the other, you have low sea water flow for any number of reasons. If both mufflers are same temp, sea flow is the same and the problem is on the coolant side.

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Can't you have a moderate amount of scale on the main heat exchanger that doesn't really affect flow so the flow will be about the same, but the heat transfer is affected resulting in overheating? In that case it could still be the r/w side.


Also the coolant side would be the last thing I would look at, but yes it might be the problem.


My bet is fouled r/w side of main heat exchanger with or without low r/w flow.



David

If impeller looks good, no need to change it now unless you want to. But do pull it out to inspect.

djmarchand said:

Can't you have a moderate amount of scale on the main heat exchanger that doesn't really affect flow so the flow will be about the same, but the heat transfer is affected resulting in overheating? In that case it could still be the r/w side.


Also the coolant side would be the last thing I would look at, but yes it might be the problem.


My bet is fouled r/w side of main heat exchanger with or without low r/w flow.



David

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How would that come on so suddenly though? I’m trying to wrap my head around the sudden change. I thought a fouled heat exchanger would be a gradual change.

Could be vanes from old impellers clogging the heat exchanger. Sounds like you have checked everything before the raw water pump. Did somebody dive on the raw water intake? Could be a plastic bag on the outside strainer if you have one. What does the exhaust elbow look like? Could be rotted / clogged internally.

Yep, sudden change has me focusing on impeller or some clog. Fouling does tend to come on slowly, but it can go un-noticed if engines are run easy THEN run harder.

Steve, are you now in warmer water than before?

Check your coolant too. Additives fail and old coolant is useless, can cause damage by cavitating around the cylinders, which can cause overheating. My keel-cooled boat would overheat and overflow the collector bottle until I changed the coolant. All 200 litres of it.

This may not solve YOUR problem but it should not be ignored.

I would jump in the water and check for crap (eg plastic bag) in the seawater inlet to the affected engine before doing anything else.

Yes, the impeller vanes could have taken a set so unless you pull it out you can’t tell. You may have bits of impellers stuck in the heat exchanger. You can run some Barnacle Buster through it. I dropped 5 degrees on one engine and 10 degrees on the other engine. Probably not the immediate problem but something to put on your todo list. The aftercoolers are no longer available at at per what I am told by American Diesel. If yours goes bad you can run a hose around it and then you have a 180 hp engine per Brian. You also could have a buildup of old zincs in the heat exchanger.

How was the water flow at survey and generally pre-purchase? If it was good, something has changed
The brand new impeller may suggest someone was chasing a cooling issue.
Perhaps the impeller was replaced but no one went hunting for the bits of its predecessor.

It takes about 5 minutes to open up the heat exchanger. Take off both caps to get a look through so you can see if many of the tubes are blocked up. If they haven't been opened for a while, the rubber gasket might be ruined when you open it. That gasket isn't anything special, you can cut one from a generic piece of rubber (epdm works well) - thickness doesn't even matter much.

Because this is a new boat to you, there is the possibility that an older impeller was destroyed and pieces of it are blocking the flow. To test where you have a blockage, you can disconnect hoses at different points of the seawater cooling loop. Start with the one right after the impeller. Start the engine and see if plenty of water flows out at you. If it does, you know the problem is after the impeller.

Do this when the engine is cold, and don't run it for too long; if you're nervous, have a friend or partner watch the temperature gauge with their finger on the stop button. It takes quite a while for an engine to overheat from a cold start without seawater running through it so you should have plenty of time.

Steve91T said:

Hey guys. We’ve out about 20 hours on the boat since we got her a couple of months ago. On our last trip towards the end of a 5 hour day, we decided to push the power to 1900 RPM or so for a bit. After about 15 minutes or so the starboard engine alarmed, water temp was 200. Port engine was still 175 or so. We throttled both back to 1500 RPM and the temps returned to normal. We anchored for the night and I decided to deal with it the next day if we still had a problem. Well sure enough, once under way the following day, the starboard engine alarmed even though we never got over 1600. We dropped the anchor and cleaned the strainer, which was pretty full. It didn’t seem to make a difference as it alarmed again in just a few minutes. We shut it down and continued on one engine. I thought for sure it was the impeller. I couldn’t track one down so we just continued the rest of the 2 day trip on the port engine, firing the starboard engine just for docking. Once at the new marina, I pulled the cover off the impeller and to it looks brand new. So that ain’t it. The strainer is clean I have water flow out of the exhaust, just not as much as there usually is. Being that this came on so suddenly, I would think there’s a blockage somewhere. But how could anything get past the strainer?

I’m headed to the boat early next week, if anyone has any experience with this and has any tips or tricks to help me figure this out, I’d really appreciate it.

Thanks
Steve

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Ah, so you *could* push the rpms over 1900 recently and no overheat, right? So if it is something that has come on quickly and recently, it sounds like a partial clog. The impeller looks good to you, but maybe change it anyway, if it's obvious that the water flow is lower than it used to be, that is indicative of the problem, the trick is to find out what is restricting the flow. There could be an issue with the raw water intake like something blocking the intake screen if you have one. or there could be a bunch of junk in the heat exchanger that has moved around to the point where it is causing a restriction. Don't forget the raw water injection into the exhaust elbow - the raw water can't get through if it can't get out and sometimes those elbows can get clogged with scale. It could also be a hose that's delaminating internally. Hopefully not because those can be hard to find.

I think the first thing to do is check the input side of each heat exchanger. Quite a lot of junk can collect in those. I have a feeling that if you found the strainer pretty full that something got past it and is clogging the heat exchanger.

Ken

Westiculo said:

It takes about 5 minutes to open up the heat exchanger. Take off both caps to get a look through so you can see if many of the tubes are blocked up. If they haven't been opened for a while, the rubber gasket might be ruined when you open it. That gasket isn't anything special, you can cut one from a generic piece of rubber (epdm works well) - thickness doesn't even matter much.

Because this is a new boat to you, there is the possibility that an older impeller was destroyed and pieces of it are blocking the flow. To test where you have a blockage, you can disconnect hoses at different points of the seawater cooling loop. Start with the one right after the impeller. Start the engine and see if plenty of water flows out at you. If it does, you know the problem is after the impeller.

Do this when the engine is cold, and don't run it for too long; if you're nervous, have a friend or partner watch the temperature gauge with their finger on the stop button. It takes quite a while for an engine to overheat from a cold start without seawater running through it so you should have plenty of time.

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Also, forgot to note that if you want to do this without draining all your coolant, you need to pinch the fat hoses on either side of the heat exchanger with clamps. Don't pinch the hoses near where they bend because there might be wire inside them. You'll have to top off the coolant after for the stuff that drips through and the stuff contained within the heat exchanger.

Thank you guys so much for all of the help. How likely is it that a bag or something gets stuck in the intake? I would think that running for hours at 7.5 kts with that engine off would clear whatever is in there, but maybe not?

To answer some questions.

Water flow during survey was strong. And it was unchanged until....it changed.
I’m in cooler water now than when we bought the boat just because of the fact that it’s winter now.
I know it’s a raw water issue because the temps come up equally and once they get to the point where the thermostat opens, the starboard engine will, at that point, start climbing very slowly. And it’s obvious I have a restriction due to the fact that the amount of water being pumped out the exhaust is reduced.

To be clear, the aftercooler (intercooler) is the part that you can’t get anymore, correct? That doesn’t have coolant in it, just charged air from the turbo and sea water. So I can pull that end cap off and see what’s going on in there.
The engines heat exhchanger has the coolant and by pinching the lines I’ll reduce the amount of coolant loss.

As far as cleaning the exhchsger itself, other than physically removing whatever junk I find, are there any special tools required? I’d be much easier for me to get them now and bring them with me rather than once I’m there. I saw a YouTube video that showed someone using a small dowl to clean out the smal tubes. I’m just not sure what the inside of my exchanger looks like and if it’s similar or not.

Thank you again!
Steve

I'm not sure about the aftercooler, but for the main heat exchanger I believe if you only pull the end cap off there is only raw water in there - no coolant loss. As for the smaller heat exchangers you will need to pull the hose off the end to see if they're clear.

Ken

Do the simplest, easiest thing first - check the raw water inlet outside the vessel. No reason to think a sucked -in bag or other debris will free itself under way. If not the direct cause, at the very least you will know the problem is somewhere else in raw water feed. I always go for the easiest answer first - quite often it works!!

Chrisjs said:

Do the simplest, easiest thing first - check the raw water inlet outside the vessel. No reason to think a sucked -in bag or other debris will free itself under way. If not the direct cause, at the very least you will know the problem is somewhere else in raw water feed. I always go for the easiest answer first - quite often it works!!

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My dock neighbor is a diver. He said he’d check the inlets for me. Obviously for some beer money.

Forgot to mention that he’d do that. I’m just wondering how often something like that happens?

Before you disassemble the intercooler, I would talk to Brian at AD. He told me the parts are not available anymore so I would ask him what is likely to happen if you take it apart. The heat exchanger isn’t too hard to work on and parts are supposed to be available. I would think that if you picked up a bag that the engine would eventually overheat even at low RPM.

Steve91T said:

My dock neighbor is a diver. He said he’d check the inlets for me. Obviously for some beer money.

Forgot to mention that he’d do that. I’m just wondering how often something like that happens?

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Not sure where you are located but diving on the thru hull should be a DIY task. Has happened to me once in 40 years. Could happen twice in the same day. Just luck of the draw.

Follow a methodical diagnostic procedure from the sea water inlet downstream:

1. First get an objective read on the raw water flow by removing the raw water hose to the injection elbow and putting it in a bucket and start the engine from cold. See how long it takes the bucket to fill at idle. Do the same with the other engine. The exhaust hose will be fine for a few minutes if you start from cold. Also look inside the injection elbow raw water inlet for any blockages.

Then follow these steps:

1. Shut off the thru hull and remove the hose from the strainer to the engine and then open the thruhull. You should see water gushing out. If not you have a blockage in the inlet, hose or strainer.

2. Remove the hose at the raw water pump and do the same.


If both of those flow lots of water, assuming that both are below the waterline then:

3. Remove the hose from the raw water pump and start the engine. You should see lots of water gush out at idle. If it is approximately the same low flow as at the exhaust injection elbow then your raw water pump is bad: impeller or worn cam.

4. The main heat exchanger is usually the first in the flow path downstream of the raw water pump. It is where impeller vanes and zinc pieces can accumulate and it is where tubes plug due to calcium precipitating out. Remove any pieces and rod the tubes with a brazing rod or gun cleaning rod.

If you removed significant stuff or rodded out lots of blocked tubes then that is probably your problem.

5. You can also sometimes rod out the other heat exchangers but some like the tranny cooler may have a welded inlet and no removable cap. So do your best to look inside for blockages.

As noted above the after cooler is a special problem as you may not be able to reassemble it due to lack of parts if you take it apart. Also I wouldn't acid clean the whole system without first pressure testing the after cooler. Don't know how it is built but if it is like Yanmar/Cummins aftercoolers you can probably just pull off the end caps and rod out the tubes. Replace the caps afterwards with lots of sealant.

After clearing all components from the sea water inlet to the raw water injection elbow you probably won't over heat even without acid cleaning.

Good luck!

David

I’d put the heat gun on the back of the both engines and note differences. Heard numerous tales of the #6 cylinder running hot from scale or other contamination.

But perhaps even more important is to make a very brief WOT runup and measure the temps including the back cylinder. But if you’re not getting rated rpm at WOT your engine is overloaded and may overheat with another variable involved like clogged flues in heat exchangers. I had a slight increase in coolant temp and found my main HE was partially clogged. I rodded it out carefully and the temp went right back to normal. You could even switch heat exchangers easily and observe if the other engine then is running hot.

Another thought is to check both thermostats. And I’ve met people that thought their engine would run cooler w/o a thermostat.

Ski in NC said:

If impeller looks good, no need to change it now unless you want to. But do pull it out to inspect.

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Ski, are these impellers like the impellers of an outboard motor in the respect that if the engine is not run for a long period of time the impellers will get stiff causing the vanes to not straighten out when they get to the wider part of the volute causing it to not pull the correct amount of water with. Especially at higher RPMs?

Yes, in a previous post I mentioned that you can’t tell if they have taken a set. If they have they won’t pump as much water. The vanes can look good while the impeller is in the pump but may have a set.

Comodave said:

Yes, in a previous post I mentioned that you can’t tell if they have taken a set. If they have they won’t pump as much water. The vanes can look good while the impeller is in the pump but may have a set.

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Yeah but I find it hard to believe they would take a set towards the end of a 5 hr trip.