CAT 3126 - economy / performance tuning

The marine based CAT 3126TA motor, that the diesel SR 410DAs left the factory with, was manufactured in three different HP ratings: 350HP, 385HP and 420HP. The 420HP version has different injectors, turbo, governor and rack settings. The ONLY difference between the 350HP and 385 HP version is the governor settings and rack settings...no iron changes. So, to answer the OP question, yes, there is some 'power' left on the table by CAT in the base 350HP motor in the 410DA....in fact, the 385HP version was a special order option in the 410DA but only a few came through the factory doors with that option. The 350HP motor can re-tuned to 385HP. Now, don't go expecting any blistering changes in performance if you choose that option. BUt, you would be doing the upgrade with all the CAT engineering behind you.

The factory props on the 410DA with 350HP CATs were 22 X 23. Load up the 410DA and those props won't allow the CATs to spin up to rated WOT RPM. I had my factory props re-tuned three times till I finally got them where they perform the best. Currently, they are 22 X 22 with a custom cup. They are the factory Hy Torq props.

The OP mentions EGTs and Boost. I installed a set of these guages on my motors. They are an easy 'cool mod' and provide a host of useful information. All new electronically controlled diesel motos have this info readily available to the end users in the Electronic Computer Displays.
 
The marine based CAT 3126TA motor, that the diesel SR 410DAs left the factory with, was manufactured in three different HP ratings: 350HP, 385HP and 420HP. The 420HP version has different injectors, turbo, governor and rack settings. The ONLY difference between the 350HP and 385 HP version is the governor settings and rack settings...no iron changes. So, to answer the OP question, yes, there is some 'power' left on the table by CAT in the base 350HP motor in the 410DA....in fact, the 385HP version was a special order option in the 410DA but only a few came through the factory doors with that option. The 350HP motor can re-tuned to 385HP. Now, don't go expecting any blistering changes in performance if you choose that option. BUt, you would be doing the upgrade with all the CAT engineering behind you.

The factory props on the 410DA with 350HP CATs were 22 X 23. Load up the 410DA and those props won't allow the CATs to spin up to rated WOT RPM. I had my factory props re-tuned three times till I finally got them where they perform the best. Currently, they are 22 X 22 with a custom cup. They are the factory Hy Torq props.

The OP mentions EGTs and Boost. I installed a set of these guages on my motors. They are an easy 'cool mod' and provide a host of useful information. All new electronically controlled diesel motos have this info readily available to the end users in the Electronic Computer Displays.


Mine are the 385hp versions, and would run 2250 at WOT (+/- 50rpm) with me, my wife, ~1/2 tank fresh water and black water or better, gear, fluids/ice and food for our 10day, 600 mile Great Lakes trip last August. Top speed I recall was 32mph on a flat calm day - on Lake Superior no less...

At one point later in the fall, we had 11 adults dispersed throughout the boat, it still ran great - no problems with performance to plane, but IIRC it was only capable of making 2100-2200rpms at WOT, probably to be expected with ~1500# extra people on board. :wow:

Depending on conditions, I found 1800-2000 rpms to be a nice cruising speed, favoring the lowest RPM that made the most speed that was comfortable. Wish I had recorded more data, as some of the numbers fade in my memory, but I am pretty sure on calm smooth waters I was capable of making 24mph at 1900rpm. Our fuel consumption for the entire 600mile trip was about .8mpg.

I'll get the numbers off the props and post them soon. EGT and boost gauges are nice to have - I have always added to any truck that is modded with additional fuel and/or boost. They are engine savers - especially the EGT gauge. Comparing port to starboard would be very telling if everything is happy in the engine room.

My goal is to have the boat tuned and running at peak performance by the end of this season, which will be spent doing a series of cruises out of Pikes Bay Marine, Bayfield WI. In the fall, we plan to haul her to Lake Union, Seattle where the distances will increase as we stretch her legs to explore the San Juans Island area. My dream is to cruise her all the way to Alaska.

I like to cover lots of ground, and while we are up to it, my goal is 1000-1500 cruising miles per year. Finding any fuel economy is paramount to the fuel budget. The efficiencies of going slower are understood - but getting the optimal GPH burn at the best cruise is my goal at this point. "Trawler speed" if ever, is still in my future when I tire of burning so much fuel. :grin:
 
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Your RPM numbers are WAY OFF!!!! I am going to assume that you have the factory analog tachs. If so...they are garbage. If you don't already own one, buy a laser tach and check the RPMs at the harmonic balancer. Then, while you are installing your 'cool mods' include a pair of Aetna Digital tachs. If you have a few extra boat dollars, fuel monitoring guages...Flo Scans.... and some exhaust temps sensors....Borrell......., would complete the gambit of usefull guages....IMHO.
 
Your RPM numbers are WAY OFF!!!! I am going to assume that you have the factory analog tachs. If so...they are garbage. If you don't already own one, buy a laser tach and check the RPMs at the harmonic balancer. Then, while you are installing your 'cool mods' include a pair of Aetna Digital tachs. If you have a few extra boat dollars, fuel monitoring guages...Flo Scans.... and some exhaust temps sensors....Borrell......., would complete the gambit of usefull guages....IMHO.

Okay Dom, you just spent my fuel budget on "cool stuff"...but we are now sitting in the slip.
:smt101

I am pulling these numbers from my 48yr old memory, and yes all gauges are factory OEM stuff... What numbers would you want/expect to see? i.e. Where are they way off? On second read I think the common 24mph cruise required more RPM...closer to 1950 or 2000...
 
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You should be turning 2800rpms at WOT. I cruise at around 2300 at 22-23kts. If your tachs are accurate then you're overloading your engines big time. You're probably leaving a lot of soot on your transom which is unburnt fuel. Once you get everything spec'd out, you should see about 1.1-1.2mpg.
 
You should be turning 2800rpms at WOT. I cruise at around 2300 at 22-23kts. If your tachs are accurate then you're overloading your engines big time. You're probably leaving a lot of soot on your transom which is unburnt fuel. Once you get everything spec'd out, you should see about 1.1-1.2mpg.


Its my memory, not the tachs. Didn't spend much time at the upper RPM limits, other than to verify that the engines would turn close to the target RPM that I researched prior to the sea trial. IIRC, they were at the target RPM (2800) only when the boat was unladen - i.e. me and the salesguy before closing. After wife, gear, fuel, water I didn't spend much time at WOT but remember that max RPM was about 150 below that target, which would be 2650 @ ~32mph.

No transom sooting. Oil was only 10hrs in and honey clear when I bought the boat, by the end of the season it had just turned from brown to black, indicating no heavy sooting internally. It was still translucent and similar port to starboard at 50+ hrs in.

It will be great to hit the water this spring and get some good baseline numbers established. Would LOVE to see 1.1mpg. Maybe I was too conservative on our cruise speeds, but ride/chop really dictated that. On the one flat calm day we had, I probably blew out the fuel budget with too much speed.
 
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As far as I recall, the DA models like 400/410/420/450 with CATs 3116/3126 were the most economical boats where we see 1.1MPG or better on a regular basis. 420 has the Cummins engines but still very economical boat. As others have mentioned spend the money on tuning your rig to produce rated WOT. I understand that SR does the tests on 1/2 loaded boats, but I personally try to achieve the same results with fully loaded boat (full or close to full fuel and water, all gear on board, including provisions, at least 4 people on board). IMO, if you tune your rig to run about 50RPMs over your rated WOT on lightly loaded boat it will be the best for your engines. Cummins suggests to tune our rigs to see close to 2700RPMs on 2600RPMs rated engines (at least this is the info for my 450C).

I guess, as new seasons starts you'll have number of tests to do with good room for improvement.
 
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One of the most important things for a diesel is to be able to turn up recommended WOT RPMs with a full load. Years ago, a certain boat company put the 4cyl Cummins in a 28' fishing boat, overpropped them bigtime to get impressive performance numbers and within 200hrs of running like this the engines experienced significant failures.

If your fully loaded boat is turning 150-200rpms less than recommended WOT, you should have some pitch, cup or both removed from the props asap.

When I redid my boat (www.seanile31.com) I had the engines turn 200 over recommended WOT RPM to adjust for a dirty bottom, coolers full of fish, 6 adults, etc.
 
First of all: Cats handle juicing up with very little effort or aftermath. The marine 3100 rotating assembly for a 350 is just as robust as a higher rating. The lubrication and cooling systems are identical. So it simply comes down to fuel and timing. Boost, aftercooling and oil capacity improvements are going to help with the upper rpms and continuous duty rpm rating.

My thoughts on what your trying to accomplish are simple but... It seems the simple things can become complicated.

If I had your money and my Cat experience here’s what I’d do: <Find the cruising sweet spot of your hull, where it likes to run up on plane with not too much effort. <Then record rpms and fuel rate in a rough attempt to calculate HP needed to move the hull at target cruising speed.
With the above data; Look into prop and governor tuning.


FWIW: If you had Cummins power this project would be impossible…. just sayin
 
Well, with respect to CATS, the 3208 was a bulletproof engine until they squeezed too much HP out of the block. I won't touch a 3208 at 435hp. Just because you can get the HP from the engine doesn't mean you should.

You can do it with Cummins as well, the 6B series is easy to change HP settings.

To the original point, even getting 50hp from your engines won't make much of a performance difference. If you want to see the different fuel burn specs at specific RPMS and HP ratings just google the fuel burn, it's consistent and all depends on the RPMs.
 
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One of the most important things for a diesel is to be able to turn up recommended WOT RPMs with a full load.Years ago, a certain boat company put the 4cyl Cummins in a 28' fishing boat, overpropped them bigtime to get impressive performance numbers and within 200hrs of running like this the engines experienced significant failures.

If your fully loaded boat is turning 150-200rpms less than recommended WOT, you should have some pitch, cup or both removed from the props asap.

When I redid my boat (www.seanile31.com) I had the engines turn 200 over recommended WOT RPM to adjust for a dirty bottom, coolers full of fish, 6 adults, etc.

I believe that this is a very important point, and appreciate you reinforcing it.

Q: If a boat is overpropped (as in your example) but not run at WOT, will the damage still occur? (I am not planning to do this, just trying to understand the theory behind matching HP and props...)

(Also, how cool would it be to meet Roger Waters?)
 
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First of all: Cats handle juicing up with very little effort or aftermath. The marine 3100 rotating assembly for a 350 is just as robust as a higher rating. The lubrication and cooling systems are identical. So it simply comes down to fuel and timing. Boost, aftercooling and oil capacity improvements are going to help with the upper rpms and continuous duty rpm rating.

My thoughts on what your trying to accomplish are simple but... It seems the simple things can become complicated.

If I had your money and my Cat experience here’s what I’d do: <Find the cruising sweet spot of your hull, where it likes to run up on plane with not too much effort. <Then record rpms and fuel rate in a rough attempt to calculate HP needed to move the hull at target cruising speed.
With the above data; Look into prop and governor tuning.


FWIW: If you had Cummins power this project would be impossible…. just sayin


My thoughts exactly, and the purpose of this thread.

During the darkest days of the recession, when diesel spiked in price and demand for all services fell, I had to find every nickel to keep my trucks on the road. We basically had more TIME at our disposal, so slowing down was a start. I knew each truck had better mileage potential, and started tuning to that specific target speed. It didn't save my company from downsizing, but we did improve cash flow, and started shaving 5-10% off fuel consumption.

I'd love to save even 5% off my cruising fuel bill, while making same or better on-plane performance.

The best cruise speed (as conditions allowed) I found was 24mph. If I recall correctly, this was about 2000-2100 rpm. I was far more engaged with learning the autopilot and navigating 600miles of Great Lakes than I was focused on efficiency, and was also working old fuel out of the system, changing RACORs as they plugged with algae, etc.

So next season my first trip will be set up to gain some good cruising numbers, with a plan in place to find the 'sweet spot' and tune to that. My mileage should be better now that the fuel system is clean, filters new, injectors have a few tanks of good fuel through them.
 
Well, with respect to CATS, the 3208 was a bulletproof engine until they squeezed too much HP out of the block. I won't touch a 3208 at 435hp. Just because you can get the HP from the engine doesn't mean you should.

You can do it with Cummins as well, the 6B series is easy to change HP settings.

To the original point, even getting 50hp from your engines won't make much of a performance difference. If you want to see the different fuel burn specs at specific RPMS and HP ratings just google the fuel burn, it's consistent and all depends on the RPMs.

Agreed - 50hp increase on a 385hp powerplant will not change speeds or on-plane performance in a noticeable way. However, it has been my experience that in certain cases, that last 50hp + correct injection timing can yield BIG savings in fuel consumption at your target RPM.
 
The way I understand it is, you want to match fuel delivery with RPM's, otherwise you're dumping too little or too much fuel per ignition. Dumping too much fuel into a cylinder will not ignite it all, wash the oil off the liner, etc... So prop tuning and making sure the fuel rack is all calibrated will probably yield good results. Just getting everything to factory spec will get you a 60% increase in economy from the numbers you threw out, no need for fancy doodads or super blowers or boostermabobs. Much better than the 5% you're looking for.
 

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