Lehman 120 running temp

I bought one on Amazon that fits my 225 Lehman. It is currently unavailable but one like it should work.


8MILELAKE 14pc Auto Cooling System Radiator Color Cap Pressure Tester Kit Aluminum Adapters w/Case

Both my Lehman 120's run at around 175 degrees, but it is important to bear in mind that both the temperature senders and the gauges are getting rather old and of course are uncalibrated.
The important thing to remember is that if they run at a particular temperature, it is when they deviate from that temperature that it becomes significant and requires immediate investigation. With 2 engines, only one is likely to change unless there is an electrical problem which say reduces the voltage in the instrument panel.

Check your engine operations manual. My Caterpillar 3116 will indicate high temp and pressure if the oil level in the crankcase is too high, even just a little. Oil on top of the crank froths, changing viscosity and temp. This really freaked us out the first time I saw it. Then I found a note in the operations manual explaining it. So, ... read your operations manual?

Selidster said:

I thought my Lehman 120 overheated today. It always sits at 162 degrees while underway or idling. Comes up to temp and stays there. Today after changing fuel filters and running it afterwards the temp jumped to 190. I immediately shut it off. My manual says it should run 175 to 190 but 195 is optimum. I'm questioning my guage a bit now. What temp are other Lehman's running?

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i also have a lehman 120 that has been overheating - 200 degrees.
the first strep in figuring out what is wrong thought is to test the engine temp. i use a hand held heat sensor and it shows a temp about 20 degrees less than the gauge.
i have a new thermostat that opens at 190 degrees which is what is required. it was not difficult to replace.
there are other problems that affect heating but it is good to get advice from someone who can look at the engine, assess hoses etc, check out the heat exchanger and then confirm you do not have leaking head gasket.

Selidster said:

I thought my Lehman 120 overheated today. It always sits at 162 degrees while underway or idling. Comes up to temp and stays there. Today after changing fuel filters and running it afterwards the temp jumped to 190. I immediately shut it off. My manual says it should run 175 to 190 but 195 is optimum. I'm questioning my guage a bit now. What temp are other Lehman's running?

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I used to run mine fine at 195. The gauges are not perfect and have a tolerance of 7 to 10 percent or 14 to 19 degrees. When in very hot summer days it began to rise up to 205, I realized that the cooling capacity was wearing off. Usually, a stuck thermostat, or low amount of coolant, or coolant refill cup leak caused the system to not suck back coolant when the engine cooled down.



There are other potential causes for engine overheating. For example, a propeller seriously fouled up with barnacles will have the engine overheat and produce lower boat speed for a given engine RPM. In my case, I would lose up to 2 miles per hour of speed for the same engine RPMs due to the propeller being severely fouled with barnacles, Other potential causes include excessive Cutlas bearing friction, transmission gear bearings, bent shaft and vibration, engine oiling system and poor mist generated by injectors.



Te most likely cause from one week to another with the boat not operating are the fouled propeller and the leaky coolant re-filler cap. When the engine is cold after a hot run, the coolant overfill reservoir should have the coolant level change a bit. I had one case where the reservoir was leaking coolant into the bilge drop by drop. I discovered the problem by placing paper towels under the reservoir bottle. The next week, the dry paper towels had the distinctive color of the coolant. It was a $5 fix I could have spent thousands chasing it. Look always for the most plausible first.


Rolo

Lehman 120

Selidster said:

I thought my Lehman 120 overheated today. It always sits at 162 degrees while underway or idling. Comes up to temp and stays there. Today after changing fuel filters and running it afterwards the temp jumped to 190. I immediately shut it off. My manual says it should run 175 to 190 but 195 is optimum. I'm questioning my guage a bit now. What temp are other Lehman's running?

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I have a 36 year old Lehman with 7700 hrs that has been very well maintained. It runs at 180. I have been told by several knowledgeable sources that 180 is the optimum running temp.

Hi long time lurker ... 1st time poster .. woo hoo (I guess being in precautionary covid isolation has some advantages!)

Had a very similar situation on my delivery voyage, Grand Haven to Lk Ontario.

Turned out that the coolant was leaking from heating coil in the tucked away potable water heater. Easy to by-pass this circuit to check.

When topping up the coolant, venting using the system using the vent valve (aft left of expansion tank, engine at idle and cool), really sped up getting the cooling system purged of air and truly full.

Graham Lindfield

Lady Morgana

GB32 - 457

Comodave said:

If it was the heat exchanger then wouldn’t the coolant go out the exhaust? Mine is dropping into the drip pan under the engine sometime over the winter.

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Colder temps cause more contraction of the block and freeze plugs,I'd have a look there to start with.

180 to 185 on my 135’s. I do an engine check every couple of hours using a infrared thermometer gun. I measure the bump underneath the header tank on the front of the engine at the same place each time which confirms the instruments.

Sadly the problem is a cracked manifold. The crack is above the center two exhaust ports. Expensive repair.

Good luck!

Graham_l said:

Turned out that the coolant was leaking from heating coil in the tucked away potable water heater.

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I'm hoping that is my problem. I went down to the boat (first time in two weeks) and looked close at the heater hose connection to the potable hot water heater. The part of the old hose sticking out past the hose clamp was all cracked and moist even when cold and with no pressure in the system. If it dripped under pressure it would flow right into the bilge under the shaft. Since the packing gland drips, any coolant mixed in would get pumped out occasionally.

Time for all new hose to the water heater aft and the Red Dot heater forward. I found an online vendor that sells heater hose in 50' lengths. That would eliminate quite a few splices in the present system.

Question: Any problem with just running a single loop through the Red Dot and then back to the water heater? The Red Dot would be served first and then circulated back to the hot water heater. Any temperature loss wouldn't be of too much concern because the hot water tank seems to get way to hot as it is right now. (Is there a thermostatic shut off for the coolant to the tank?) If not, two valves close by the block would allow shutting things down in case of a leak or for repairs/replacement. Is this too simple of a setup?

Mark

Soo-Valley said:

Oops, just remembered, I also replaced both rad caps. Only 4lbs.

The pressure pump reminded me.

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Since these are older style, larger diameter, low pressure caps you have to be careful that your replacement cap is a coolant recovery cap with the second sealing disk. Caps of this size and pressure rating were very common on older cars and equipment which did not have coolant recovery bottles. Those caps lack the second seal that causes the coolant to be sucked back into the expansion tank as the system cools.

Island Cessna said:

Since these are older style, larger diameter, low pressure caps you have to be careful that your replacement cap is a coolant recovery cap with the second sealing disk. Caps of this size and pressure rating were very common on older cars and equipment which did not have coolant recovery bottles. Those caps lack the second seal that causes the coolant to be sucked back into the expansion tank as the system cools.

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Thanks I got the one that cross matched the original equipment part number

Possibly, a hose connection, gasket leak or a crack that only leaks when under some pressure and/or when cooled fully or partially. When hot, the places of possible leaks will be heat expanded, therefore they self seal until cool. Once cooled to a point things shrink allowing a leak. Possibly not noticed when hot and/or when the pressure is equalized. When pressure is equalized the leak may be reduced to nil. I have seen all three of these leak possibilities. Something to consider.

Turns out I have a cracked manifold. Letting coolant into an exhaust port. No fun.

Great you identified the issue. Keep us posted on the repair.

Depending on your heat exchanger and zincs you may be breaking off part of the zinc when you install if the zinc is a little long. It’ll hit the back edge and snap off when you tighten. So if you’re going through zincs really fast that may be part of it

Here is the cheapest 4# radiator cap that I could find for a Lehman. $8 on Amazon Prime and I could have returned it if it didn't fit. This isn't the coolant overflow type (which I didn't need). An "official" Lehman cap at a marine store might cost $25. I suppose I could paint this one red.

It didn't solve my coolant loss issue, but I'm one step closer.

https://www.amazon.com/gp/product/B000IVL6SG/ref=ppx_yo_dt_b_asin_title_o09_s00?ie=UTF8&psc=1

Ignore the title about a cam-shaft seal. Amazon often has an erroneous description. I use the part number (and Amazon Prime in case things get screwed up).

10281 Stant or
31307 Gates or
703-1419 NAPA

These are all rare around here

Marco Flamingo said:

Here is the cheapest 4# radiator cap that I could find for a Lehman. $8 on Amazon Prime and I could have returned it if it didn't fit. This isn't the coolant overflow type (which I didn't need). An "official" Lehman cap at a marine store might cost $25. I suppose I could paint this one red.

It didn't solve my coolant loss issue, but I'm one step closer.

https://www.amazon.com/gp/product/B000IVL6SG/ref=ppx_yo_dt_b_asin_title_o09_s00?ie=UTF8&psc=1

Ignore the title about a cam-shaft seal. Amazon often has an erroneous description. I use the part number (and Amazon Prime in case things get screwed up).

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If I'm not mistaken, the Lehman 120 requires a 7# cap. I'm not at my boat right now. I'd Call American Marine in Norfolk. They have the proper cap, whatever it is.

Bryant said:

If I'm not mistaken, the Lehman 120 requires a 7# cap. I'm not at my boat right now. I'd Call American Marine in Norfolk. They have the proper cap, whatever it is.

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https://www.fredwarner.net/product/...k-cap-marine-diesel-engine-2715e-2712e-2c302/