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Old 08-07-2016, 01:45 PM   #1
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Lehman Stalls at Crucial Times

So it was pointed out to me that I should change my fuel filters more often as I was having stalling problems portside Lehman 80 - the starboard seemed to be ok but I changed 4 filters on each engine as the engines were due for regular maintenance anyway. portside seems to be ok now but starboard stalls now. The worst part of this is the stalls happen just after I have pulled back on the throttles to approach the dock. (performance was great at cruising speed for hours...) I can start the engine again right away so no vapor lock I think but anyone with twins will know that when you lose an engine the steering goes to hell NOW !...not good when you are trying to bring in a 13 ton boat...any ideas ?
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Old 08-07-2016, 02:03 PM   #2
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stalling at critical time

Interesting.... We have twin Lehman 120's and in the 5 years we have owned it one engine has quit once. That was exiting the narrow harbor entrance with a big swell running and a boat under tow approaching as the engine alarm sounded and the boat started veering to port. Once I figured out what was happening, the engine restarted with no problem and has never stalled again. I was not having a bad dream and would like to understand what the issue was.

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Old 08-07-2016, 03:26 PM   #3
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Originally Posted by Tangler View Post
So it was pointed out to me that I should change my fuel filters more often as I was having stalling problems portside Lehman 80 - the starboard seemed to be ok but I changed 4 filters on each engine as the engines were due for regular maintenance anyway. portside seems to be ok now but starboard stalls now. The worst part of this is the stalls happen just after I have pulled back on the throttles to approach the dock. (performance was great at cruising speed for hours...) I can start the engine again right away so no vapor lock I think but anyone with twins will know that when you lose an engine the steering goes to hell NOW !...not good when you are trying to bring in a 13 ton boat...any ideas ?
Check you throttle cable travel.
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Old 08-07-2016, 04:03 PM   #4
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I had a 120 Lehman that drove me crazy with a capricious stall - turned out to be a little bitty screw on the injection pump. I was in despair having traced checked everything and suddenly a tiny bubble formed and popped on this screw. An "aha" moment! I removed the screw, annealed the tiny copper washer and screwed it down again, never another stall problem. Good luck finding yours, it's an air leak 100%.
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Old 08-07-2016, 07:50 PM   #5
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Check you throttle cable travel.
I had the same problem on one of my 120's. Indeed it was the throttle cable travel. On my injector pump the travel was a simple adjustment of the threaded portion at the end of the cable where it attaches to the pump. A few turns had it idling at the proper RPM without it shutting down when backing down of the throttle lever to full idle.
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Old 08-07-2016, 08:14 PM   #6
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What's your idle rpm?

Also if you're overpropped rpm will drop considerably when you put it in gear.

I'd prop to rated rpm and raise the idle speed.

Another thought is that if the throttle is'nt comming down hard against the set screw you may have various idle speeds.
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Old 08-08-2016, 06:13 AM   #7
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IF it stalls shifting at docking it could be you are not pausing long enough for the shaft and prop to stop spinning.

It doesn't take much power to get a stopped shaft started , but if its spinning in the opposite direction much more is needed, for a short time.,

Even coasting in one direction in neutral can cause a higher shaft load when shifting to stop the vessel..
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Old 08-09-2016, 06:57 AM   #8
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sounds like when you swapped filters you didnt bleed all of the air out.

the pump needs to have the fuel bleed bolt bled and you may even need to crack open the injector hoses (fully unscrewed) until a solid flow of fuel comes out. the bleed bolt needed to be loosened and retightend and then reloosened several times before the main fuel cavity was bled all the way.

then on top of that you may need to run the motor 30 minutes continuously, so says the shop manual.
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Old 08-09-2016, 07:58 AM   #9
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This gets my vote: "it's an air leak 100%", although 100% might be more like 90, especially since you state that the problem has switched sides.
My lehman started doing this after a maintenance session. Turned out I had developed a leak in a "T" fitting in the fuel lines.
Recheck the seating on your filters, then recheck everything else.
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