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Old 08-01-2011, 11:32 AM   #21
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RE: 120 Lehman overheating

Another quick question; I'm trying to order the impeller, is the original model number for the Jabsco pump 5850-0001?

The boat is a 1981 35 CHB tri cab with a 120 Lehman.

As far as I can tell, the Jabsco part number for the impeller is either 1210-0001 (neoprene for water only) and 1210-0003 for the same impeller in nitrile (which is rated for also pumping other fluids including oil and fuel).

Thanks Guys!
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Old 08-01-2011, 01:00 PM   #22
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RE: 120 Lehman overheating

Quote:
RickB wrote:

To eliminate the chance of confusing terms, EGT is normally measured in the exhaust gas path as near to the exhaust valve as practical.
*On our engines the EGT or pyrometer probe is mounted in the water-cooled elbow attached to the rear of the exhaust manifold.* The probe is installed just upstream of the water injection point.* So they are a fair distance from the exhaust valves themselves.
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Old 08-01-2011, 01:11 PM   #23
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120 Lehman overheating

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tomtomterrific wrote:
I was cruising at 6-7 knots which is normal, tachs read 2500 RPM at this speed (but may read high)
*
*You either have a very different version of the FL120 than just about everyone else or you have more than just an overheat problem.* Or you mistyped.

The redline for the FL120 is 2500 rpm.* If you're running at that rpm to get 6 or 7 knots you either have a REALLY big and heavy boat, your props have very little pitch to them, or your tachs are totally out of whack.

To get 7 knots out of our boat we have to run our two FL120s at about 1500 rpm or so.* We normally run at about 1650-1700 (the old SW tachs on our boat are not the most accurate things on the planet) which gives us about 8 knots through the water.* Our boat is 36 feet long with a semi-planing hull and it weighs about 28,000 pounds.

If your tachs are out of whack you need to get that fixed asap because without an accurate rpm reading you are operating your engines in the dark.

PS--* I bleed the exhaust manifold on each engine before each day''s start using the petcock on the front of the manifold.* I have to have the expansion tank cap off to do this properly as with the cap on it may not allow the coolant to bleed out.* Air trapped at the top front of the manifold can cause a hot spot and subsequent damage or even burn-through of the manifold.* This bleed procedure is only called out in the engine manual when changing coolant.* It is not part of the recommended pre-start checks.* Most people probably don't do it.* I do it because it's easy and is one more way of confirming everything's okay.

As noted by Tom (Sunchaser) the leak from your exhaust elbow is an indication of a problem that could become a big problem in a hurry.* I would have a mechanic familiar with these engines check it our thoroughly.* The leak indicates one of several problems depending on where it''s coming from.

According to the manual, the coolant capacity of the 6-cylinder FL120 is 20 quarts.* So if you had to add 2 gallons of coolant to get the correct level, you were replacing close to half the coolant in the engine.* It would be very enlightening to find out where that coolant went, because wherever it went, and why it went there, do not sound like situations that will fix themselves.* Unless the coolant level had never been checked and the loss of coolant was gradual over a long period of time.

The advice to run the whole situation past Bob or Brian Smith at American Diesel is good.* While it's hard to impossible to accurately troubleshoot over the phone these guys have seen just about everything that can happen to a Lehman-marinized engine so may be able to tell you exactly what's going on.


-- Edited by Marin on Monday 1st of August 2011 01:39:57 PM
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Old 08-01-2011, 01:48 PM   #24
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RE: 120 Lehman overheating

Marin,

I replaced all the gauges with new Teleflex/Morse units 3 years ago.* The tachs*have never been*properly calibrated.* I have not been able to figure out how to do this.* Let me know if you know how.* I believe that I'm running ~1600 RPM @ 7 knots.* Boat is ~18,000 lbs, is properly propped and bottom is clean.***

I'll double check the "drip" on the exhaust elbow.* It's*where*the exhaust manifold mates with the exhaust elbow.* Ahead of the muffler and just*above the port side of the heat exchanger.*Since the HX is newly painted I noticed a small stain there so I assumed there was a "drip."* I'll monitor more closely to confirm.

*

Thanks!
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Old 08-01-2011, 02:00 PM   #25
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RE: 120 Lehman overheating

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tomtomterrific wrote:
Marin,

I replaced all the gauges with new Teleflex/Morse units 3 years ago.* The tachs*have never been*properly calibrated.* I have not been able to figure out how to do this.* Let me know if you know how.
Our boat is equipped with its original SW tachs.* Or if they aren't original the replacements are the same make and model.* They are electric and they get their signal from an electro-mechanical sender mounted on the side of the engine.* So I can't give you any insight into adjusting your TM units other than get a pro down to do it.
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Old 08-01-2011, 03:29 PM   #26
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RE: 120 Lehman overheating

I Googled your problem and got this but*I agree with Marin.* Get some help.

http://www.jamestowndistributors.com...hometer+Gauges
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Old 08-01-2011, 05:19 PM   #27
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RE: 120 Lehman overheating

Quote:
tomtomterrific wrote:
Marin,

I replaced all the gauges with new Teleflex/Morse units 3 years ago.* The tachs*have never been*properly calibrated.* I have not been able to figure out how to do this.* Let me know if you know how.*
*You will need a hand held strobe tach to calibrate your Teleflex tachometers. Those hand helds are pretty inexpensive now, I think I've seen them for $40 online. You stick a piece of reflective tape (that comes with the tach) to the harmonic balancer on the front of the engine. Then start up and take a reading. There should be instructions with the tach to show you how to do this. On the back of your boat tachs there should be a small hole with an adjustment screw. You'll need a jewler's screwdriver or a glasses repair sized screwdriver. Then at the dock in neutral you set the throttle to some rpm, hopefullt around 2000 works best. Take a reading with the handheld, then adjust the boat tachs to that reading.

I like to have a helper adjust the rpm to an even number like 2000 on the handheld, then I adjust the boat tachs accordingly.

Simple proceedure takes about 1/2 hour to complete.

I probably missed a step, but I have done it so many times for myself and others I take the procedure for granted and don't even think about it.

*

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Old 08-04-2011, 02:00 PM   #28
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RE: 120 Lehman overheating

Update...

Replaced the impeller today. It had 4 blades broken off and another 2 cracked, so this was definitely the culprit.

There is no active drip from the exhaust elbow. Just a stain.

Picked up a IR thermometer gun and having some fun with it. The trans runs at 138 degrees.

Ordered a photo tach and will be looking at calibrating the tachs next!

Thanks to all for your help.

This weekend's family cruise is back "on!"

Tom
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Old 08-04-2011, 02:10 PM   #29
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RE: 120 Lehman overheating

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tomtomterrific wrote:
Update...

This weekend's family cruise is back "on!"

Tom
*Terrific, Tom!!
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Old 08-04-2011, 02:50 PM   #30
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RE: 120 Lehman overheating

Just a thougt, but an important one, did you find all of the broken and missing impeller rubber? I am in the process off rebuilding the water pumps on my twin Perkins, so this is fresh on my mind. I found most of the broken impeller rubber in my heat exchanger, where it was blocking several tubes. Some was actually in the tubes. I removed this with a long thin needle 'awl; that I bent a small fish hook barb on the end while heating it with a propane torch so as not to break it. Some was stuck in the pump discharge goosenecks. I saved all the chunks and compared it to the broken impeller to be sure all the missing rubber was accounted for. Certainly not a good situation if left behind.
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Old 08-04-2011, 04:38 PM   #31
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RE: 120 Lehman overheating

If you change out your impellers every 12* - 18 months you won't be digging out pieces and overheating. Has anyone seen an impeller crater in a year - excepting run dry periods?
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Old 08-04-2011, 08:29 PM   #32
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RE: 120 Lehman overheating

A quick question on impellers. Broken impellers are always a potential problem, they are pretty flimsy things. Are there more robust options out there?*

Impellers have*always seemed to to be the achilles heel of the Lehman.(apart from its water pump)

Regarding the post, I would still be a little concerned as to where 2 gallons of fresh coolant got to, and why, the broken impeller pump doen't account for it.
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Old 08-04-2011, 11:46 PM   #33
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120 Lehman overheating

Quote:
shrimp wrote:
Impellers have*always seemed to to be the achilles heel of the Lehman.(apart from its water pump)

*As the owner two Lehman 120s for the past 13 years I have not found that to be the case at all.* We do not change our impellers every year or even every other year.* We change them every 200 - 300 hours, whenever I feel like dealing with it during that envelope.* Granted, we use the boat year round so the impellers are not sitting in one position for weeks on end.* And about five years ago we switched from the stock raw water system to the 1" Johnson pumps.* But in both cases--- Jabsco and Johnson--- the impellers that came/come out look exactly like the impellers going in.* In fact every time I do it I ask myself why I didn't leave them in for another 100 hours or so.


-- Edited by Marin on Thursday 4th of August 2011 11:47:52 PM
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Old 08-05-2011, 04:55 AM   #34
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RE: 120 Lehman overheating

Broken impellers are always a potential problem, they are pretty flimsy things. Are there more robust options out there?

My way is a Y style strainer after the pump that simply catches the impeller pieces. Inspection is fast and easy .

When the imperller fails , no attempts at back flushing (to hope to get all the chunks) is required.
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Old 08-05-2011, 11:14 PM   #35
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RE: 120 Lehman overheating

Having lost an engine to an impeller failure, I am a little nervous of repeating the experience.
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Old 08-09-2011, 01:17 PM   #36
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RE: 120 Lehman overheating

Guys,

A quick follow up question. Anyone know where I can get paper gaskets for the jabsco pump seperately?

I had to a gaskets from the second kit I had as well as some sealer on the R&R of the impeller.

So now I'm shrot a gasket for the second kit. I'd also like to get some spares in case I run into the same issue again.

Thanks!

Tom
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Old 08-09-2011, 01:29 PM   #37
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RE: 120 Lehman overheating

Quote:
tomtomterrific wrote:
Guys,

.....Anyone know where I can get paper gaskets for the jabsco pump seperately?...

*Tom:* The Jabsco part # is:* 3298-0000*

Just google it.
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Old 08-10-2011, 05:55 AM   #38
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RE: 120 Lehman overheating

Thanks Larry!
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Old 08-11-2011, 06:48 PM   #39
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RE: 120 Lehman overheating

i had a weird engine overheat problem that was eventually traced to loss of coolant occurring from minute cracks in the water heater hoses abrading on the bulkhead between the engine room and water heater. the tiny cracks caused loss of coolant and it was a devil of a time finding where the coolant was coming from as it was running down the inside of the bulkhead on the water heater side and ending up in the bilge. i kept noticing that i had to top up the coolant overflow container after each long run, and that the temp was running hotter than usual. but there was no coolant drip or loss under the engine area. i even taped a terrycloth towel 'diaper' under the engine to see if i could find any drips out of say the antifreeze on-engine pump. finally with engine cold, i got a stant tester , put it on the radiator cap, and pressurized the the coolant system to about 7 psi. i saw a huge jet of coolant blowing past the heater hoses where they entered the bulkhead.. problem solved for about $50 of new hoses (now installed with abrasion protectors ...). i also put in a borel exhaust temp alarm as a double check on the engine's own overheat alarm..
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Old 04-08-2013, 10:02 AM   #40
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I am in need of a face plate gasket for my jabsco water pump on my ford lehman 120. Can anyone point me in the right direction. I am also replacing the pencil anodes on the coolers,,are they 1/2 inch in size. Thanks.
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