Risingson
Active Member
Did those pumps come with the gear on them? Or do you use the gear from the old pump?
Official Caterpillar3116/3126 Thread
- Thread starter carterchapman
- Start date
my understanding is no gear but we’ll see what shows up next week
- Jun 5, 2016
- 5,551
- Boat Info
- 410 Sundancer
2001
12" Axiom and 9" Axiom+ MFD
- Engines
- Cat 3126 V-Drives
They do not come with a gear. I used an impact wrench to get the nut loose and swapped over. I used a punch to knick a thread to make sure the nut was captured.
did the gear just pop off the taper then?
Idle speed question - I have mine set to 700RPM no load idle, they drop 60-70rpm or so in gear (both sides) so the low idle in gear is about 630. It creates a bit of vibration and if I add a few revs back they smooth right out
my question, what is your in-gear low idle rpm? Does it drop from your neutral rpm as well?
my question, what is your in-gear low idle rpm? Does it drop from your neutral rpm as well?
- Jun 5, 2016
- 5,551
- Boat Info
- 410 Sundancer
2001
12" Axiom and 9" Axiom+ MFD
- Engines
- Cat 3126 V-Drives
I cant remember getting the gear off, I may have used a gear puller, or put the nut over the threads and hit with a mallet while bracing the gear. Regardless, wasn't hard.
On the other hand, I've considered buying 2 new gears and building a backup set.
Risingson
Active Member
When I changed my starboard pump. The easy side. I couldn’t get the gear off so my yard mechanic did it for me and also measured where the gear was on old shaft so he could press the gear on the new pump shaft in the exact location
So the gears are aligned perfect.
- Jun 2, 2008
- 5,023
- Boat Info
- 1998 450 Sundancer, Achilles dinghy w/15hp
- Engines
- 3126 Cat's
Port side is the easy one in my ER...
920richardf
Member
I'd go for 750rpm no-load idle. Will leave you about 700rpm with gear engaged.
I like that, I might bump up. No concern with transmission wear at that rpm?
- Jun 5, 2016
- 5,551
- Boat Info
- 410 Sundancer
2001
12" Axiom and 9" Axiom+ MFD
- Engines
- Cat 3126 V-Drives
What is the procedure to set the idle? My port is very low 585-615 when cold but gets closer to the starboard at about 650 as it warms up.
are those numbers in gear or no load?
You disconnect the throttle linkage, bring the idle screw on the throttle stop down to 650 and then use the buffer slotted screw on the side of the governor to bring the idle up to desired 700-750. This process must be done with the engine at operating temp
I’ll find the official procedure wording and post here
Carver370
Well-Known Member
- Mar 30, 2007
- 1,927
- Boat Info
- 2000 Sea Ray 400 Sundancer - Diesel
- Engines
- T-3116 CAT - 350 HP
FYI that buffer screw is very touchy. Make sure to give the throttle a few bumps after adjusting the screw.
I have also found that different adjustments to the buffer screw and the idle stop net different reactions when put into gear.
I have also found that different adjustments to the buffer screw and the idle stop net different reactions when put into gear.
Yep, same on ours and it really MUST be at operating temp or you get a completely different result
- Jun 5, 2016
- 5,551
- Boat Info
- 410 Sundancer
2001
12" Axiom and 9" Axiom+ MFD
- Engines
- Cat 3126 V-Drives
I'm looking for a diagram of whats what...
- Jun 5, 2016
- 5,551
- Boat Info
- 410 Sundancer
2001
12" Axiom and 9" Axiom+ MFD
- Engines
- Cat 3126 V-Drives
I'll have to pay more attention next time out to get better numbers...I know I have to bump the port up...it drives me crazy
I'll take pictures tomorrow, the pics in the service manual are horrible.
Ok gurus, try and save me a call to CAT 
I have made significant headway on my overpropping issue from last year when I bought the boat. We were seeing over 950* EGT and only 17 PSI of boost at WOT. Port RPM was as low as 2680 and startboard was even worse at 2608
I cleaned aftercoolers, compressor side of the turbos, replaced all boost hoses and clamps. I also straightened my starboard strut as it was bent and aligned the engine. Both sides can be turned easily in neutral by hand (I needed a wrench to turn the starboard last year) and I also replaced both cutlass bearings.
Props were tuned, balanced, and cut to 21.5" pitch with a target of 2850 loaded RPM.
I went for a ride today, almost full fuel, very little water, all of our gear, and I was alone so 1POB. I am seeing VERY good boost and in my opinion WOT speed and RPM but I still have a high EGT on the starboard side at cruise RPM and slightly low boost compared to the port.
I note that I have full tabs but backing the tabs off did not decrease the EGT in a meaningful way.
What is next? I do know the previous owner was chasing a low WOT issue with CAT and they did some playing with fuel and governor settings. I don't want to get them out if I can avoid it but that might have to happen to reverse anything they did.
No black smoke, a tiny bit of soot on the transom but this was the first ride of the year so maybe she needed her pipes blown out.
I know it's close, but I'm not really comfortable running 900* EGT all the time at cruise. The CAT service manager said the sea trial data for our engine is 761*F EGT +/- 8% so I'm almost 80* high
Oh, one other thing. CAT won't send me exactly what was done last year because the previous owner didn't pay the invoice. They did share that the fuel settings were messed with. Maybe overfueling causing low boost/high EGT?
I have made significant headway on my overpropping issue from last year when I bought the boat. We were seeing over 950* EGT and only 17 PSI of boost at WOT. Port RPM was as low as 2680 and startboard was even worse at 2608
I cleaned aftercoolers, compressor side of the turbos, replaced all boost hoses and clamps. I also straightened my starboard strut as it was bent and aligned the engine. Both sides can be turned easily in neutral by hand (I needed a wrench to turn the starboard last year) and I also replaced both cutlass bearings.
Props were tuned, balanced, and cut to 21.5" pitch with a target of 2850 loaded RPM.
I went for a ride today, almost full fuel, very little water, all of our gear, and I was alone so 1POB. I am seeing VERY good boost and in my opinion WOT speed and RPM but I still have a high EGT on the starboard side at cruise RPM and slightly low boost compared to the port.
I note that I have full tabs but backing the tabs off did not decrease the EGT in a meaningful way.
What is next? I do know the previous owner was chasing a low WOT issue with CAT and they did some playing with fuel and governor settings. I don't want to get them out if I can avoid it but that might have to happen to reverse anything they did.
No black smoke, a tiny bit of soot on the transom but this was the first ride of the year so maybe she needed her pipes blown out.
I know it's close, but I'm not really comfortable running 900* EGT all the time at cruise. The CAT service manager said the sea trial data for our engine is 761*F EGT +/- 8% so I'm almost 80* high
Oh, one other thing. CAT won't send me exactly what was done last year because the previous owner didn't pay the invoice. They did share that the fuel settings were messed with. Maybe overfueling causing low boost/high EGT?
Last edited:
- Jun 5, 2016
- 5,551
- Boat Info
- 410 Sundancer
2001
12" Axiom and 9" Axiom+ MFD
- Engines
- Cat 3126 V-Drives
Here's the Spec's that CAT publishes for the 2001 350 hp version of the 3126 TA. Yours should be identical.
Boost pressure is listed in Hg guage. Conversion is 2.036 in Hg --> psi Ex @ 2400 RPM boost = 38.1 = 18.7 psi.
@ WOT rpm approx 27 psi and around 1060*F
@ 2400 rpm approx 19 psi and around 810 *F
@2200 rpm approx 13 psi and around 760*F
Ambient air and water temperature, air pressure, relative humidity will have an effect. There is very little boost until you start getting over 2000 rpm.
The only thing I see that is a little out of spec is the EGT @ 2200 rpm, but its not terrible. Go rerun the numbers at 2300 rpm, and 2400 rpm. You might see the EGT come down slightly as you get more boost (air) at those higher rpms relative to fuel. That might be out the window if they changed the fuel delivery.
Boost pressure is listed in Hg guage. Conversion is 2.036 in Hg --> psi Ex @ 2400 RPM boost = 38.1 = 18.7 psi.
@ WOT rpm approx 27 psi and around 1060*F
@ 2400 rpm approx 19 psi and around 810 *F
@2200 rpm approx 13 psi and around 760*F
Ambient air and water temperature, air pressure, relative humidity will have an effect. There is very little boost until you start getting over 2000 rpm.
The only thing I see that is a little out of spec is the EGT @ 2200 rpm, but its not terrible. Go rerun the numbers at 2300 rpm, and 2400 rpm. You might see the EGT come down slightly as you get more boost (air) at those higher rpms relative to fuel. That might be out the window if they changed the fuel delivery.
Thanks Dave. I also torqued the aftercooler bolts down to spec, I completely forgot I didn’t have my torque wrench when I installed them after cleaning so maybe I had a slightly boost leak
as a test I just swapped gauges too since the scale is 300-1300 I could easily have some variance there.
Next time I’ll get better data and record it as I go. I’m thinking 2000-2400 rpm tests in increments of 100 and record all the numbers.
Still waiting on CAT to get back to me about the fuel thing though.
