Ford Lehman 80 overheating

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RobClipper30

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Joined
Dec 22, 2020
Messages
18
Happy Holidays to you all!

I'm a bit of a novice so please forgive any wrong terminology or wrong descriptions.

My Ford Lehman 80 is overheating. It usually runs at full throttle (and a roaring 6 knots) and the engine temp hovers around 180/190 degrees celsius.

Recently it's been getting up to 210/220 degrees and so hot there's a fair bit of white smoke out the exhaust and the radiator cap even blew off.

I've checked and there's plenty of oil, plenty of coolant. There was a lot of growth on outside underside of boat so I had the divers around. They said the sea water intake had some growth now removed. Here's a video of the seawater cooling system in action at about 75% throttle.

Is that functioning correctly? I noticed that when at a decent throttle the water level in there is low, it's like it's sucking out all the water waiting for the new stuff to flow in, not constantly filled. Not sure if that's a problem..

Separate to that (or perhaps another cause/problme) I believe I now hear a 'whooshing' type noise in the engine which wasn't there before. I can't diagnose where it is (or if it's even in my imagination...)... but if the sea water cooling system is functional perhaps something else is wrong..

Any ideas greatly appreciated!

Rob
 
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Hard to really tell from the video but step through these checks:
Start by checking the water flow outside (exhaust). Is it same as it has been?

1) Thru hull to seacock/strainer: Assuming the thru hull is below the water line if you open the top of that strainer basket (crack it a little) you should have significant water flow. If not probably something growing/clogging the through hull or a problem with the hose (they do build up crud inside).
2) Strainer basket/seacock: Assume the seacock is actually fully open? Strainer is clean?
3) Next stop is the hose from strainer to engine (seawater pump). Crack hose entering seawater pump and see if you get water flowing out
4) Seawater pump: This contains a rubber impeller. If I had to guess this likely is where you have the problem so frankly I MIGHT JUST START WITH THIS STEP!! remove the 4-6 screws on the cover plate. Pull out the rubber impeller (an impeller puller is highly suggested but you can use pliers). Before you do you should already have a few spares onboard for this. Likely you will find the tangs are damaged. Unless this is fairly new and undamaged install a new one.
5) If no of the above their are probably 2 more possible items I can think of
6) Coolant pump (pumps the antifreeze through the heat exchanger. Don't think this is your problem as it seems you are having an issue with the seawater side and not the coolant side.
7) Heat exchanger on the engine. If you found a failed impeller you need to open this up anyway as you have to find all the missing rubber pieces of that impeller. If you open up the end caps you likely will also find the little copper tubes are clogged. You can clean it carefully with a wood or metal rod but probably best to have a radiator shop boil and pressure test it. But for Lehmans you can get a new one (American Diesel, Brian) for not much more and unless you know the age of the old one I would start new and get a baseline.

One other thought, check the temp of the exhaust water flowing out the stern of your boat. If it is cold then you probably have a failed coolant pump (engine driven, step 6). You can have great flow on the seawater side but if the coolant is not being pumped through the heat exchanger the coolant is getting really hot and seawater stays cold even though you have great flow. Replacing the engine driven pump is not that hard either and you probably can get one from Brian.

Hope this helps!
 
I had a slowly rising temp on a Yanmar at about age 15. At WOT or high cruise, temp would slowly rise. Using Rydlime to clean the raw water circuit didn't help much. Engine dealer suggested draining the AF and use Prestone radiator flush/cleaner on a run, to open the thermostat, then drain and use fresh water for a run, then drain and repeat until clear instead of brown water is drained. Then, drain the water and replace with AF. That made a HUGE difference and solved the problem. What's most interesting, every AF change, the AF always looked like it was brand new since the boat was new from the factory. YMMV

Clark
 
Simple things first. Do you have adequate water flow out of the exhaust at idle? What is the condition of the impeller?
 
Robclipper30,

Is this a Tung Hwa Clipper 30? If so, what is WOT and why only 6 knots?

Here is my WAG. If I understand, when you run at high rpm you get an air pocket in your strainer. Your bottom and intake had been fouled, according to divers. If your raw water pump is working as it should, and your raw water intake is clogged beyond the strainer (inside your hull strainer, through-hull, intake hose), you could be creating a vacuum in that line. A weird possibility is that you are sucking air in downstream of the strainer (or even at the strainer seal) at higher rpm. Hose connections and strainer seals can be tight enough to not leak water out at low psi, but under a strong vacuum they can let air in.

Can't think of any other reason air would show up in the strainer (unless you are getting up on plane!!!) Water restriction and air intrusion could have the affect of reducing the water by half or more. Not quite problematic over-heating, but too close for comfort.

My other thought when hearing the video was to adjust the valves. I also have a Lehman 80 and, like the 120, they clackety-clack even when adjusted properly. I assume that, as with a gas engine, valve adjustment effects thermal efficiency.

Be very careful with high temps. My fan belt was loose because the stainless pivot bolt on the alternator shattered. The slippage stopped the water pump from working. I overheated and scored the crankshaft beyond being repaired. I sourced another one in England (probably the last one on Earth). $19K later I was back on the water. Don't do what I did!!

Mark
 
I agree with everything Ready stated, that would be your first point of action, but recently I heard something else, that I have never heard of before.
I think it was on a Youtube channel of 'will fix that' a mechanic in Key West. Any case, the mechanic stated that sometimes the cooling openings in engines can get clogged up, so he flushed them with a normal dish washing detergent.
Don't know if he was making up stuff or whether that is true. If anyone knows anything about that, would like to hear it.

One thing I missed in the list of Ready is the flow rate of the thermostat. If the thermostat cannot pass enough water when it opens up you could end up in trouble as well.
 
Thanks to everyone who has taken the time to help!

I’ll go through the diagnostic steps I can (with my novice ability) from the above help and revert back.

Thanks again and stay tuned :)

Rob
 
Always check for impeller bits. There's always something. LOL
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Anything Ford Lehman you need to talk to Brian at American Diesel. They are Ford Lehman and he has all the parts and more importantly, the complete knowledge of Ford Lehman (his dad developed it).
American Diesel (The Lehman Ford Experts).
 
Hi Rob,

In your original post when you engine was running happily I suspect "spell check" took over and of course it was running around 180 deg F. It looks to me from your video that the raw water flow seems very low for 75% throttle. Is the strainer below the water line ? if you removed the lid would it overflow ?. Your engine is trying to reject all of its heat energy into this flow. If the raw water flow is too low to build back pressure, ie. completely full the heat exchanger (and I expect the strainer bucket) it would become highly inefficient with the raw water not coming into contact with enough surface area of the cooling tubes. Did you happen to notice what the flow in the strainer looked like when things were ok or like most of us only go looking when Murphy showed up?. Of course a lot of other things may be hindering the engine temperature, but I would maybe firstly seek other FL 80 owners to get an idea of what the raw water flow looks like. The Lees guys here (same engine as the Lehman) dyno the raw water pumps after rebuilding them to check water flow and pressure after rebuild. But to my untrained eye it sure looks like the inlet side of you raw water pump isn't seeing enough head.
 
Hi Rob,

I just read Readys' reply - looks good, follow that.
 
Happy Holidays to you all!

I'm a bit of a novice so please forgive any wrong terminology or wrong descriptions.

My Ford Lehman 80 is overheating. It usually runs at full throttle (and a roaring 6 knots) and the engine temp hovers around 180/190 degrees celsius.

Recently it's been getting up to 210/220 degrees and so hot there's a fair bit of white smoke out the exhaust and the radiator cap even blew off.

I've checked and there's plenty of oil, plenty of coolant. There was a lot of growth on outside underside of boat so I had the divers around. They said the sea water intake had some growth now removed. Here's a video of the seawater cooling system in action at about 75% throttle.

Is that functioning correctly? I noticed that when at a decent throttle the water level in there is low, it's like it's sucking out all the water waiting for the new stuff to flow in, not constantly filled. Not sure if that's a problem..

Separate to that (or perhaps another cause/problme) I believe I now hear a 'whooshing' type noise in the engine which wasn't there before. I can't diagnose where it is (or if it's even in my imagination...)... but if the sea water cooling system is functional perhaps something else is wrong..

Any ideas greatly appreciated!

Rob
Yes, start with the simple things… when was the impeller(s) changed last? Have a look. If and rubber fins are missing chase them down in the oil coolers and do a thorough flush of the system.
Check blocked sea cocks or flow through the engines,
Have you added coolant lately ? The system might need to be bled.
Call Brian for more tips
 
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