FL 120 temperature

[Randomwake]

Just bought a 34chb trawler And have two questions :
1- Manual says optimum engine operating temp is 190, but it only gets to 150. Not sure if anyone else has encountered this? I assume I just need a different thermostat but not sure if it is deliberately set lower? Possibly to keep #6 cool as I’ve heard there can be some issues.

2- I’m trying to troll with this big brute, at high idle to
Ensure good combustion, if I’m at 900-1000rpm I should be getting good combustion eh? Don’t want any engine damage, if I’m not getting great combustion what is the harm? Just fuel dilution in the oil? Or something more?

3- it trolls too fast so I’ll be kicking it in and out of N a lot. It shifts incredibly smooth! Is this bad for the transmission or is it no diffeRent than pressing the clutch in your car?

 

[artfulltune]

Hello Random, are you just using your gauges? Try a laser or infrared thermometer for comparison. Then check your thermostat, if there is one.

 

[catalinajack]

Just bought a 34chb trawler And have two questions :

1- Manual says optimum engine operating temp is 190, but it only gets to 150. Not sure if anyone else has encountered this? I assume I just need a different thermostat but not sure if it is deliberately set lower? Possibly to keep #6 cool as I’ve heard there can be some issues.



2- I’m trying to troll with this big brute, at high idle to

Ensure good combustion, if I’m at 900-1000rpm I should be getting good combustion eh? Don’t want any engine damage, if I’m not getting great combustion what is the harm? Just fuel dilution in the oil? Or something more?



3- it trolls too fast so I’ll be kicking it in and out of N a lot. It shifts incredibly smooth! Is this bad for the transmission or is it no diffeRent than pressing the clutch in your car?

After confirming the temp with an infrared thermometer, if your operating temp is, in fact, 150 degrees you should consider changing your thermostat to a 180-degree model. My FL120s, with 180 thermostats run at 182 degrees as measured by a high-quality Fluke IR thermometer. Running too cold, over time, risks fuel dilution of your lube oil. I found this out (oil analysis) by using 160-degree thermostats for a time, a poor decision.

 

[DavidM]

Your thermostat may be stuck in the open position. A quick test to confirm is to run the engine at wot for 5 minutes after it is warmed up to 150. If it quickly rises 20-30 degrees, it is likely stuck open.

David

 

[Tator]

I'm sure it can be a bit harder on the transmission to keep shifting it in and out. That being said, we too troll by shifting our B-W trannies and have been doing it for 15 years. We also spent many years and hundreds of hours shifting them in and and out while researching and recording humpback whales. Keeping your rpms below 850 and shifting slowly will help. It's the flex plate that will go. We also have flexible couplings on our shafts that help absorb the shock. Of course...they could go out tomorrow. And be sure and run your engine at 180deg and run it hard for a few minutes after running it at trolling speeds.

Tator

 

[SteveK]

Stop shifting to obtain troll speed. Why high idle, what is wrong with just idle.
Check the thermostat. If it is rated 180 and running 150 it could have had a hole drilled to prevent air getting trapped. At idle that is enough flow to keep temp lower.

 

[Cigatoo]

I think that the "earlier" Lehmans came with 150 degree thermostats. They were later changed to higher temps such as 190. You can email American Diesel with your questions / parts requests. It would be helpful to have the engine serial number included in the email.

 

[Marco Flamingo]

My thermostat had a hole drilled in it and wouldn't heat properly at anything below about 1,800 rpm. There were lots of places where pole holders had been attached on my boat, so I know that the boat was used for trolling and would not have heated properly with a hole drilled in the thermostat. Also, one of the prior owners had installed the heavier Lehman flywheel (100# instead of 87#) to smooth out the idle when trolling. Usually used on the 120 Lehman, I've got one on my 80hp. Smooth idle but probably takes a couple extra seconds to spin up to start.

Stant makes a 180 degree Ford thermostat (PN 45358) that has a "micro channel" that doesn't trap bubbles. No need to buy a "Lehman" specific thermostat. It's a Ford. For $10, you might as well buy one and install it if you're even thinking of looking at your old one. When I took my old one out I saw that it was a 170 with a hole drilled in it, so not even worth keeping as a spare. Stant (and others) also makes a 190 degree for Ford, but I thought I'd split the difference.

 

[catalinajack]

I'm sure it can be a bit harder on the transmission to keep shifting it in and out. That being said, we too troll by shifting our B-W trannies and have been doing it for 15 years. We also spent many years and hundreds of hours shifting them in and and out while researching and recording humpback whales. Keeping your rpms below 850 and shifting slowly will help. It's the flex plate that will go. We also have flexible couplings on our shafts that help absorb the shock. Of course...they could go out tomorrow. And be sure and run your engine at 180deg and run it hard for a few minutes after running it at trolling speeds.



Tator

Tator, those flexible couplings are not flexible. They do not absorb shock. They fracture when their torque rating is exceeded.

 

[catalinajack]

My thermostat had a hole drilled in it and wouldn't heat properly at anything below about 1,800 rpm. There were lots of places where pole holders had been attached on my boat, so I know that the boat was used for trolling and would not have heated properly with a hole drilled in the thermostat. Also, one of the prior owners had installed the heavier Lehman flywheel (100# instead of 87#) to smooth out the idle when trolling. Usually used on the 120 Lehman, I've got one on my 80hp. Smooth idle but probably takes a couple extra seconds to spin up to start.

Stant makes a 180 degree Ford thermostat (PN 45358) that has a "micro channel" that doesn't trap bubbles. No need to buy a "Lehman" specific thermostat. It's a Ford. For $10, you might as well buy one and install it if you're even thinking of looking at your old one. When I took my old one out I saw that it was a 170 with a hole drilled in it, so not even worth keeping as a spare. Stant (and others) also makes a 190 degree for Ford, but I thought I'd split the difference.

Marco, my 180-degree stats have holes and the boat warms quickly to 182 degrees and stays there even at less than 1,600 RPM.