Official Caterpillar3116/3126 Thread

[Strecker25]

How much stuff do you guys think you might have accumulated? It might take a lot to really affect rpm and load but I picked up my sons toy bin today and swear it’s 200lbs.

just saying, maybe there’s lots of extras on board? I went from 2860 to 2805 just between April and august and I’m fAirly certain it’s mostly us just putting more junk on the boat

 

[Riptide III]

soiled aftercooler could lower boost subsequently lowering WOT, but I’d think it would have to be a pretty serious case to drop 100+ rpm.

do you have boost gauges?

I do not
Also load is probably less than it has ever been. I just remembered that I tried to adjust the throttle levers to make them even(no luck). It is possible they are no longer touching the stops. I will check them tomorrow

 

[ttmott]

I do not
Also load is probably less than it has ever been. I just remembered that I tried to adjust the throttle levers to make them even(no luck). It is possible they are no longer touching the stops. I will check them tomorrow

You might consider single engine load testing to ensure both engines stall at the same RPM.

 

[Riptide III]

You might consider single engine load testing to ensure both engines stall at the same RPM.

What is that? Is that just checking one engine at a time with he other in neutral to see which is the lower one?

 

[ttmott]

What is that? Is that just checking one engine at a time with he other in neutral to see which is the lower one?

It's an important load test which checks the basic health of each engine independently. Run each engine at full throttle independently and see what the stall RPM is. You may have to do the test a couple of times as it tends to blow out the prop. Bring the RPM up slowly to prevent blow-out. If, for example, one engine pulls to (stalls) at 2100 RPM and the other only makes 1600 RPM there is probably some issues with that engine or it's drive gear; it's not making the power of the first.

 

[dtfeld]

I done the one engine at a time both stalled at the same RPM, but don't recall exact number.

I think it might be load. The reason I've been testing is I'm going to repitch or re prop now that I have the boat the way I want it. For me it may be windage. I have added a rolled up aqua mat and a SUP board to the front rails. I guess easy enough to remove and retest to see if that make a difference.

Just want to rule out any other issues before deciding.

 

[fwebster]

The boat has been running well with the exception of higher than normal temps. Today I opened her up to check full throttle RPMS. I usually do it at the beginning of the season but this year I didn’t. 25kts 2660 rpms both sides. Usually it’s 2800rpms. Clean bottom(just pulled last week). Aetna tachometers (installed a few years ago). No smoke. Airseps cleaned 20 hours ago.
This is the fifth season(about 475 hours) since cleaning aftercoolers. Could that have an affect on rpms or cooling. I have 3116 so afercooler is not raw water cooled.

The recommended after cooler maintenance interval on 3116's is 1000 hours or 4 years (for a Northern recreational boat the 4 year interval isn't applicable.) Unless you have been using a multi-viscosity oil, it is very unlikely that you have noticeable fouling in the intake passages of the after coolers and if you do, there would be a lot of soot on the transom after a day on the water.

On the overheating issue, what coolant are you using and have you ever changed it? Cat ELC is great because you don't have to monitor the SCA levels in thew coolant, but you do need to change the coolant every 4-5 years in a recreational boat. The coolant will break down and it can coat the internal passages where the antifreeze lives. When that happens the coolant deposits actually inhibit the transfer of heat in the heat exchanger and the operating temps begin to rise.

and, David. . . . . on Cat engines with the unit injection system (3116 & 3126), if any air enters the injection system it goes to the fuel gallery that feeds all 6 injectors. Air cannot be processed so it shuts down any injector that it hits. Therefore, if you had air in your fuel system, you wouldn't experience a decrease in RPMs, instead the cylinder the air gets to, stops firing and you get a dead miss. If it happens on cylinder #6, you just get a miss on #6 but the engine will run on 5 cylinders; however, if it happens on #1 thru #5, the air is pushed on to the subsequent cylinders, and the engine cannot sustain rpms and will probably die.

 

[Riptide III]

On the overheating issue, what coolant are you using and have you ever changed it? Cat ELC is great because you don't have to monitor the SCA levels in thew coolant, but you do need to change the coolant every 4-5 years in a recreational boat. The coolant will break down and it can coat the internal passages where the antifreeze lives. When that happens the coolant deposits actually inhibit the transfer of heat in the heat exchanger and the operating temps begin to rise.

and, David. . . . . on Cat engines with the unit injection system (3116 & 3126), if any air enters the injection system it goes to the fuel gallery that feeds all 6 injectors. Air cannot be processed so it shuts down any injector that it hits. Therefore, if you had air in your fuel system, you wouldn't experience a decrease in RPMs, instead the cylinder the air gets to, stops firing and you get a dead miss. If it happens on cylinder #6, you just get a miss on #6 but the engine will run on 5 cylinders; however, if it happens on #1 thru #5, the air is pushed on to the subsequent cylinders, and the engine cannot sustain rpms and will probably die.

I use the NAPPA green at the recommendation of my CAT mechanic. He said it is also ok. I would like to hear your opinion on that. Also, if an inferior product were used would some type of flushing be required and if so, what would you suggest? Thank you

 

[fwebster]

I prefer Cat ELC because the engine maker formulates it to match and support the continuing needs of their engines. By the same token, like many aftermarket supplies, it may be almost impossible to find out what NAPA's supplier adds to their coolant for anticorrosives, anti cavitation in the black and anti foaming. With any non Cat coolant, I suspect you will need to test the coolant at least annually for ph, and SCA 's. One of the advantages of Cat ELC is that it has a 4-5 year life in recreational boats, so when you do change the new coolant needs nothing for a long time except for checking the level as a part of your pre-departure check list.



Now . . . . . the above are the advantages and why using Cat ELC is practical and cost effective but the NAPA Green is a general Ethylene Glycol coolant for use in automotive and light duty diesel truck applications. Here is a quote from the NAPA website:

"NAPA Antifreeze/Coolant Is A Conventional (Green) Ethylene Glycol Based Antifreeze For Automotive & Light Duty Diesel Applications."

The Cat owner's manual clearly says that Ethylene Glycol meets Cat's minimum coolant requirement provided you dilute it 50/50 with distilled water and that you add Cat's recommended SCA 'S and check and replenish the SCA's periodically as needed.

Napa does offer a prediluted version of the NAPA Green coolant. They say it has SCA's in it, but we have no way od knowing if they meet Cat's requirements which are determined based on the metals used in manufacturing Caterpillar engines.

 

[Riptide III]

Houston I think we have a problem.

I would think that would cause my engine to run a little warmer than usual.

 

[Strecker25]

Houston I think we have a problem.
View attachment 110600
I would think that would cause my engine to run a little warmer than usual.

wow! I’d say so

 

[Pour Excuse]

Hello
I am new to this club so please instruct if this is not the area to be asking this question
I have recently purchased a 97 400 sedan bridge with twin cats
In my documentation there are conflicting methods to starting and stopping these engines.
On the start it instructs to push the rocker up and wait for lights. I only get engine cranking and starting engines? There does not appear to be any preheat operation.
On the port engine rocker if I rock the switch down I notice a load on the battery voltage. Could this be the preheat? The starboard rocker does not load the batteries that I can see.

The only method that I can see to turn the units off is the emergency stop rocker but my cat documentation warns that this is a damaging process
Any help would be great

 

[Strecker25]

Hello
I am new to this club so please instruct if this is not the area to be asking this question
I have recently purchased a 97 400 sedan bridge with twin cats
In my documentation there are conflicting methods to starting and stopping these engines.
On the start it instructs to push the rocker up and wait for lights. I only get engine cranking and starting engines? There does not appear to be any preheat operation.
On the port engine rocker if I rock the switch down I notice a load on the battery voltage. Could this be the preheat? The starboard rocker does not load the batteries that I can see.

The only method that I can see to turn the units off is the emergency stop rocker but my cat documentation warns that this is a damaging process
Any help would be great

@dtfeld posted the official cat documentation I think but in order to cycle the AIH properly you should push the rocker switch to the run position (invaluable tip - press the button on the SR monitor panel to silence the buzzer temporarily) and wait 30 or so seconds until the battery voltage returns to normal indicating the first heating cycle has completed. You can now start the engine

if your one engine isn’t loading the battery when cold it might be disconnected or malfunctioning. The heaters come on if the coolant is below a certain temperature, I think it’s around 140

if you don’t want the heaters to run I believe starting the engine without letting them complete the startup cycle will defeat them until the next cycle of the ignition circuit

 

[dtfeld]

What Ryan stated is correct at least for 3126's with air inlet heat. 3116's are pretty similar, but I cant speak to that aspect of them, I've never looked specifically at the 3116's

My bet is they are pretty similar.

If you are not getting a big voltage drop on your starboard engine, its possible you have a bad connection or a bad solenoid that controls the air heaters on/off. I had one go bad, it was about $75, and a pretty easy swap out.

 

[Steve S]

Hello
I am new to this club so please instruct if this is not the area to be asking this question
I have recently purchased a 97 400 sedan bridge with twin cats
In my documentation there are conflicting methods to starting and stopping these engines.
On the start it instructs to push the rocker up and wait for lights. I only get engine cranking and starting engines? There does not appear to be any preheat operation.
On the port engine rocker if I rock the switch down I notice a load on the battery voltage. Could this be the preheat? The starboard rocker does not load the batteries that I can see.

The only method that I can see to turn the units off is the emergency stop rocker but my cat documentation warns that this is a damaging process
Any help would be great

I have a 2000 400DB (Sedan Bridge) with 3116's. As far as I know, there is no Preheat position, only the "Run" detent and when pushed all the way, the "Start" mode. The "Run" position energizes the solenoid which turns on the fuel pump.

I am not sure if we have Air Inlet Heat. I will have to check for the voltage drop/restore the next time I am at the boat.

Now from the "Run" position when the engine is running, I simply press the bottom of the switch and the engine stops.

 

[Pour Excuse]

Thank you
I will investigate as there isnonly one cranking battery and there might have been alterations to the heating circuit

Is the emergency stop rocker the correct method to kill the engines?

I have a 2000 400DB (Sedan Bridge) with 3116's. As far as I know, there is no Preheat position, only the "Run" detent and when pushed all the way, the "Start" mode. The "Run" position energizes the solenoid which turns on the fuel pump.

I am not sure if we have Air Inlet Heat. I will have to check for the voltage drop/restore the next time I am at the boat.

Now from the "Run" position when the engine is running, I simply press the bottom of the switch and the engine stops.

 

[Pour Excuse]

Thanks for the info
Somethings definitely different with my boat
Pushing down on the start run will not kill the motors at this time????

 

[fwebster]

Neither engine has glow plugs or a preheat position. The auxiliary intake air heater was only installed on 3126's. Those delivered in Florida didn't even have the intake heaters on them. I never saw a need or a way to control the intake heaters operation. they are controlled by the engine temperatures. When you start a 3126, if it is cold enough the intake air heater comes on and then it goes off by itself when the engine warms sufficiently. You can check the operation with a volt meter or the simple man's way is by watching the voltage gage on the panel. When the heaters operate, there is a significant drop in voltage and when the heaters cycle off, the volt meters go back to normal readings.

 

[ttmott]

What Ryan stated is correct at least for 3126's with air inlet heat. 3116's are pretty similar, but I cant speak to that aspect of them, I've never looked specifically at the 3116's

My bet is they are pretty similar.

If you are not getting a big voltage drop on your starboard engine, its possible you have a bad connection or a bad solenoid that controls the air heaters on/off. I had one go bad, it was about $75, and a pretty easy swap out.

I didn't think the 3116's were offered with heaters (grids or glow plugs). My 2000 400DA with these engines didn't have them. Regardless, turn the keyswitches on make sure the gear is in neutral and throttles closed then click the ign on and further depress to crank and start - that's it. To shut down depress the ign switch to off (down).
The Emergency start only combines the batteries so get around a battery problem for engine start.
Depress the Emergency start switch and hold it while starting the engine of choice; then release. Whom ever told you that things can be damaged using the emergency start switch is wrong - there is nothing you can do to damage anything other than holding on the engine start switch after then engines have fired off.
There isn't many things simpler that the engines and systems to operate them than what you have....

 

[Pour Excuse]

Neither engine has glow plugs or a preheat position. The auxiliary intake air heater was only installed on 3126's. Those delivered in Florida didn't even have the intake heaters on them. I never saw a need or a way to control the intake heaters operation. they are controlled by the engine temperatures. When you start a 3126, if it is cold enough the intake air heater comes on and then it goes off by itself when the engine warms sufficiently. You can check the operation with a volt meter or the simple man's way is by watching the voltage gage on the panel. When the heaters operate, there is a significant drop in voltage and when the heaters cycle off, the volt meters go back to normal readings.