Lehman 225 overheating...

Did the overheating start at the end of the 5 hour run or when you increased power at the end of the 5 hour run?

Comodave said:

Did the overheating start at the end of the 5 hour run or when you increased power at the end of the 5 hour run?

Click to expand...

Yes. But only after 20 minutes or so. Cooled down when we brought it back to 1500. The next day she alarmed within 15 minutes. We never got above 1500.

One thing I didn't mention is that it is possible for even a relatively new impeller to fail because the rubber breaks away from the bronze hub. The impeller may look fine buts its essentially "slipping". This isn't common, but it does happen.

Ken

Steve91T said:

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

Click to expand...

There is only one way to find out for sure, pull it out and see if the vanes are curved and stiff

The impeller is probably the easiest and most likely fix, however that may depend on how your engine is installed. My starboard engine impeller is very difficult to replace. The port one is easy. The starboard one can’t even be seen. I use a tool from impellertool.com along with a Jabsco puller. With those tools I can do the change. Still not my favorite job but it is possible to do.

Possible you sucked something up in front of the seawater pump? You said the strainer was full. Stuff can get past it sometimes.

Capitaine R said:

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?

Click to expand...

Possible, yet rare. Found that impellers that have a "set" to them from sitting, if given a couple of days out of the bore or with running, assume normal shape.

Check your coolant with a CAT test strip.

kchace said:

One thing I didn't mention is that it is possible for even a relatively new impeller to fail because the rubber breaks away from the bronze hub. The impeller may look fine buts its essentially "slipping". This isn't common, but it does happen.

Ken

Click to expand...

More common than you think and probably the easiest to check. It would be what I would look at 1st.

"If you hear hoofbeats, don't expect zebras."

Pick the simplest solution first.

Test your antifreeze/coolant.
Change your impellers annually and keep the old ones as spares. If the problem is not solved, dig deeper.

Tell us what you find.

BeeJay said:

More common than you think and probably the easiest to check. It would be what I would look at 1st.

Click to expand...

If rubber part comes un-bonded from hub (does happen), all pumping would be quickly lost. Not the case here.

Hey guys. Finally on the boat trying to chase down this cooling issue. I decided not to replace the impellers because of the fact that are soft, flexible and look relatively now. I do have new ones onboard though.

I opened the strainer and then opened the sea cock. Noted the water flow. Then I closed the strainer and pulled the hose off the raw water pump and opened the sea cock. Lots of water flow and no sign of sea weed or anything. Because I’m dealing with the starboard engine, the heat exchanger is going to be a bitch to get to, so I decided to start the engines, let them warm up for a few minutes then ran them up to 1600. I don’t think I have a restriction in the water flow. I honestly thought it was less than that during our last trip, but I’m not positive.

Does this rule out the heat exchanger?

Could it be the thermostat?

Here are the engines running at 1600.

https://youtu.be/jAh1yX0ql_g

Running engines at dock will not give same results as being underway will they?

Gmarr said:

Running engines at dock will not give same results as being underway will they?

Click to expand...

Water flow is RPM dependent so for what I was doing, it does.

Ok, you are part way through the step by step process. Take off the r/w hose to the injection elbow and look inside the injection point for blockages. Then do the bucket test I mentioned on both sides and compare. With that data in hand you will know what your next step is.


David

That looks like a pretty heathy flow to me. You still could have some type of restriction. When I first bought my boat the port engine would get dangerously hot if I pushed it over 1800. It turned out to be heavy scaling on the main heat exchanger on that engine. If yours are scaled, and then for some reason one got a little extra crap in it or if there are lots of bits of old zincs in it, it could be just clogged enough to cause overheat when pushed above a certain level. In any case, I think a look inside the leading ends of the first heat exchanger in the line (is it the oil cooler?) and inside the leading end of the main heat exchanger is in order.

Have you checked the antifreeze level INSIDE the coolant tank (The one with the pressure cap on it)? The level in the overflow tank may not be telling the story.

Ken

kchace said:

That looks like a pretty heathy flow to me. You still could have some type of restriction. When I first bought my boat the port engine would get dangerously hot if I pushed it over 1800. It turned out to be heavy scaling on the main heat exchanger on that engine. If yours are scaled, and then for some reason one got a little extra crap in it or if there are lots of bits of old zincs in it, it could be just clogged enough to cause overheat when pushed above a certain level. In any case, I think a look inside the leading ends of the first heat exchanger in the line (is it the oil cooler?) and inside the leading end of the main heat exchanger is in order.

Have you checked the antifreeze level INSIDE the coolant tank (The one with the pressure cap on it)? The level in the overflow tank may not be telling the story.

Ken

Click to expand...

Funny you ask...she was bone dry. I’m pretty mad at myself for letting it get this far before confirming the coolant level. It was the first thing we checked and we both swear there was coolant in the overflow.

Either way, I just put a gallon of distilled water in the tank and ran it at the dock at 1500 for about 20 minutes. She held perfectly at 170. We are taking a 2 hour trip on Friday, that’ll be the real test.


Sooooooo.....

Where’d that gallon of coolant run off to?

"Hoofbeats..."

Crap, post #4 asked you that very question. Coolant level ok?? Ans: yep, ok.

So you have a leak somewhere, look for it. Hoses shrink in cold and leak, go around, look and snug up clamps.

Ski in NC said:

Crap, post #4 asked you that very question. Coolant level ok?? Ans: yep, ok.

So you have a leak somewhere, look for it. Hoses shrink in cold and leak, go around, look and snug up clamps.

Click to expand...

Yep. I feel like an idiot. In my defense the overflow had coolant. We even added to it to get it above the minimum when cold mark. Today was the first time I’ve been back to the boat since it happened and I’m sans kinds so I had time to really check things out.

There are no coolant leaks that I can see. I ran the engine for a total of about 30 minutes today.

Idk, maybe it’s been low from the PO and it finally got to a level that it started sucking air. I’ll know more on Friday after a 2 hour drive.

Sorry guys

Steve91T said:

Yep. I feel like an idiot. In my defense the overflow had coolant. We even added to it to get it above the minimum when cold mark. Today was the first time I’ve been back to the boat since it happened and I’m sans kinds so I had time to really check things out.

There are no coolant leaks that I can see. I ran the engine for a total of about 30 minutes today.

Idk, maybe it’s been low from the PO and it finally got to a level that it started sucking air. I’ll know more on Friday after a 2 hour drive.

Sorry guys

Click to expand...

If it does end up dropping and you can find no leak it's possible to be the main heat exchanger

Once you fix the leak you will have to fix the clogged or otherwise malfunctioning expansion bottle circuit.

And verify the other engine's expansion bottle circuit is working and that engine is full of coolant. (Level in bottle should rise an inch or 2 when engine is fully warmed up and go back to exactly where it was when engine is fully cooled down)

When I bought my boat neither expansion bottle circuit worked but both bottles had coolant. If I hadn't watched them carefully and pulled the pressure caps off I never would have known.

Ken

Lehman 120 expansion tanks(? 225s) have a metal tube inside which can clogs
and need to be cleaned, even drilled out, to function.

kchace said:

If it does end up dropping and you can find no leak it's possible to be the main heat exchanger

Once you fix the leak you will have to fix the clogged or otherwise malfunctioning expansion bottle circuit.

And verify the other engine's expansion bottle circuit is working and that engine is full of coolant. (Level in bottle should rise an inch or 2 when engine is fully warmed up and go back to exactly where it was when engine is fully cooled down)

When I bought my boat neither expansion bottle circuit worked but both bottles had coolant. If I hadn't watched them carefully and pulled the pressure caps off I never would have known.

Ken

Click to expand...

A faulty radiator cap is a common cause for an expansion tank not working. Lesson learned here. Start with the simple stuff.