Fuel consumption meter on CAT 3306?

[LeoKa]

My single engine feeds from the starboard tank. The fuel comes out of the bottom of the tank and goes through rancor filters and the engine’s fuel filter. The return goes into the same tank on the top. The engine was built in 1986, so it has a metered governor/fuel injection pump.
I would like to figure out the consumption of this engine. Is there an easy and affordable solution to incorporate a flow meter somehow? Has anyone figured this out?
I know I could just start with a full tank and run some miles and fill up again. The tank is 400 gallons and I do not plan to buy diesel just for this purpose. It would be a very costly test. Plus, I would like to figure out the consumption at different rpm’s. I do not need high accuracy. I just want to know approx what I need to a certain distance, before I plan longer voyages in the near future.
Thanks.

 

[tiltrider1]

Do you have sight tubes on your tank?

 

[twistedtree]

If your engine is propped correctly, you could get pretty accurate numbers based on the engine's performance specs. There should be a published prop power curve that will show fuel consumption across the engine's RPM range. That will give you gph at each RPM point. Be sure to use the prop curve, not the max power curve. That should give you pretty good numbers, assuming the boat is propped correctly. To confirm it's propped correctly, at wide open throttle the engine should turn a bit over max rated RPM. Perhaps 25-50 rpm over. That will match the curve in the data sheet.

 

[LeoKa]

Do you have sight tubes on your tank?

There is only a cynic tube coming out of the bottom, marked with a pen for each 50 gallons. It is not very useful for measuring consumption.
The boat was custom built over 20 years ago and there is no sophisticated anything on it.

 

[LeoKa]

If your engine is propped correctly, you could get pretty accurate numbers based on the engine's performance specs. There should be a published prop power curve that will show fuel consumption across the engine's RPM range. That will give you gph at each RPM point. Be sure to use the prop curve, not the max power curve. That should give you pretty good numbers, assuming the boat is propped correctly. To confirm it's propped correctly, at wide open throttle the engine should turn a bit over max rated RPM. Perhaps 25-50 rpm over. That will match the curve in the data sheet.

Unfortunately there is not much documentation available on my boat. Certainly nothing about the prop. The CAT manual does not give me any directions on this. The engine is a turbo, industry converted/marinized engine. It was rebuilt in 1996.

 

[LeoKa]

Here are some photos.

 

[Greg QS]

This is an easy one.
1 way is the engine spec you can get online for your engine It will give you the gph per every 200 rpm or so.

Second way is use the 50 gallon marks on you tank. Run the engine at a set rpm every time you use the boat. Keep accurate distances you go and time of travel. Ignore idling time and slow under rpm times. do the math Gal/hrs = gph or gal/miles= gpm

third is fill the tank till the first click off on the hose. . fuel doesn't go bad. run for a set period of time say 3 hrs at a constant rpm. Fill back up.

If you dont trust the tank lines. Its normally pretty easy to figure out. Mark your sight tube, to to the fuel dock, put in however much fuel you would like. 50 gal? mark sight glass again if it goes up a 1/2 inch , or whatever increment, and its a rectangular tank. every 50 gals the 1/2 . if its a irregular tank this wont work.

 

[Greg QS]

You can download the spec sheet for your engine from Boat diesel. You need to be a member. Mine is expired.

https://boatdiesel.com/PDFLibrary/Index.cfm#

search 3306 and look at the data sheets tab

 

[Greg QS]

found it
diesel parts direct under cat spec sheets if below link dose not work

https://www.dieselpartsdirect.com/documents/caterpillar-specs/cat-3306b-dita-propulsion.pdf

 

[Greg QS]

just need to know where to look.
lol

 

[tiltrider1]

This is an easy one.
1 way is the engine spec you can get online for your engine It will give you the gph per every 200 rpm or so.

Second way is use the 50 gallon marks on you tank. Run the engine at a set rpm every time you use the boat. Keep accurate distances you go and time of travel. Ignore idling time and slow under rpm times. do the math Gal/hrs = gph or gal/miles= gpm

third is fill the tank till the first click off on the hose. . fuel doesn't go bad. run for a set period of time say 3 hrs at a constant rpm. Fill back up.

If you dont trust the tank lines. Its normally pretty easy to figure out. Mark your sight tube, to to the fuel dock, put in however much fuel you would like. 50 gal? mark sight glass again if it goes up a 1/2 inch , or whatever increment, and its a rectangular tank. every 50 gals the 1/2 . if its a irregular tank this wont work.

As already stated. Fill to the 50 gallon mark. Run for 3 hours or more and then refill to the same mark. Now you know.

For years I made a point of filling my boat to the same mark and then running Seattle to Friday Harbor and refilling to the same point. This verified that I was seeing the same data as published by Cat for my 3208’s.

I continue to always fill to this mark and track the data monitoring for change.

 

[Greg QS]

What is the hp of the engine.
for the 335 hp fuel burn as follows

rpm hp tor bsfc fuel
2200 355 848 .388 19.7
2100 309 773 .372 16.4
2000 267 701 .360 13.7
1900 229 633 .353 11.6
1800 195 568 .350 9.7
1700 164 507 .350 8.2
1600 137 448 .352 6.9
1500 113 395 .355 5.7
1400 92 344 .360 4.7

 

[Delfin]

Here are some photos.

View attachment 132187View attachment 132188View attachment 132189View attachment 132190View attachment 132191View attachment 132192

You are here....


Note, I have a Floscan meter on the identical engine, which matches this pretty precisely.

 

[Taras]

Yes, I too have FloScan meters on my twin 3306 Cats. The numbers from Delfin look very close to what I see on the Floscan's. Note my motors are 1990 350 hp motors

 

[LeoKa]

You can download the spec sheet for your engine from Boat diesel. You need to be a member. Mine is expired.

https://boatdiesel.com/PDFLibrary/Index.cfm#

search 3306 and look at the data sheets tab

I did. I am a member, but the data sheets are for engines starting from 1997. My 3306 was built in 1986 and it was an industrial engine originally. It was converted to marine setup by the first owner who built the boat.

 

[LeoKa]

What is the hp of the engine.

for the 335 hp fuel burn as

To my knowledge it is 220 HP.

 

[LeoKa]

As already stated. Fill to the 50 gallon mark.


I continue to always fill to this mark and track the data monitoring for change.

Yes, that is my plan, regardless of the data I’ll find. That is the best method to have the real data. CAT data sheet would be useful for comparison on a 36 years old engine.

 

[twistedtree]

I did. I am a member, but the data sheets are for engines starting from 1997. My 3306 was built in 1986 and it was an industrial engine originally. It was converted to marine setup by the first owner who built the boat.

I don’t think that will matter as long as you have the data sheet for the correct HP.

 

[LeoKa]

I don’t think that will matter as long as you have the data sheet for the correct HP.

Maybe you are correct. I still want to know as close as possible.
When bought the boat, I was told about 3-4 gallons at cruising speed. The data sheet shows between 7-10 gallons an hour. That is a big difference on a long trip.
Well, the broker lied about my keel tanks, too. It was listed as two 400 gallons tank in the keel just recently I was able to measure them accurately, and they are only 200 gallons each. Again, important misinformation for a long range trip.

 

[Delfin]

I don’t think that will matter as long as you have the data sheet for the correct HP.

Don't think that matters. You'll get higher fuel burn with an A rated motor, but only at rpms that are higher than that available for, say a C rated motor. The displacement times the rpm equals the fuel burn, so horsepower is a derivative of those values, not a driver of fuel burn.

 

[twistedtree]

Don't think that matters. You'll get higher fuel burn with an A rated motor, but only at rpms that are higher than that available for, say a C rated motor. The displacement times the rpm equals the fuel burn, so horsepower is a derivative of those values, not a driver of fuel burn.

If the extra HP is all at higher RPMs, then I agree.

 

[twistedtree]

Maybe you are correct. I still want to know as close as possible.
When bought the boat, I was told about 3-4 gallons at cruising speed. The data sheet shows between 7-10 gallons an hour. That is a big difference on a long trip.
Well, the broker lied about my keel tanks, too. It was listed as two 400 gallons tank in the keel just recently I was able to measure them accurately, and they are only 200 gallons each. Again, important misinformation for a long range trip.

I would give the broker's/owner's statements about fuel burn the least credibility. In fact, I'd probably dismiss it entirely. And besides, what is "cruise speed". Slight speed differences make huge fuel consumption differences.

 

[Greg QS]

I understand your concern on a long trip. No offence here please. It seems to me you don't have a lot of experience with traveling on THIS boat. On any boat that is new to me, I do incremental voyages. Take the vessel on a medium trip and get good data on your fuel burn before jumping into a long trip. This is also good to do as a shake down cruise to find any boat gremlins that may come up. You don't wat failures on a long trip.

When I purchased my current vessel from Florida , I went down for a check out drive for a week, taking longer and longer trips till I wound up in the keys. As I told the broker I was trying to break the boat. I did too. I got a handle on the fuel burn. I went through all the systems I could to learn them and inspect them. On the trip a bunch of items came up that had to be repaired, this was annoying but It was a good thing I did that. These items would have came up on the 1200 mile trip home causing substantial delays . Since I was able to work the kinks out of the boat, it made the trip successful without a break down. Take the boat out and run harder than you normally would for an extended period of time. This will test your systems. If all is good when you run normally you will most likely have a relatively issue free trip. You need to get her off the dock and run her. You fuel burn wont matter if you cannot get there in the first place.

I would also recommend diving into the boat and learn every nook an cranny of her. Have spares for whatever you can think of . From spare engine parts, belts, hoses, clamps, bilge pumps, oils, filters for fuel and oil. The more the better. There are no stores on the water and some times you will have to do on the water repairs. Especially in a single engine platform. Tow insurance a must.

 

[twistedtree]

I think measuring fuel burn by running a bunch and then refilling your fuel tank is a good way to get a very high level view of typical consumption. It will inherently factor in slow operation, docking, as well as steady underway operation. You can track mileage and engine hours, but you will have hours idling at the dock with no miles traveled. And how reproducible is the fill level on your tank, and the gauge on your tank. Is it +/- 1 gal? +/- 5 gal? +/- 10 gal? I'll bet mine are +/- 20-50 gal. That will introduce a huge inaccuracy into any calculations.


The above is a good thing to do, but it's not going to give you a plot of gph and nmpg at various RPM operating points. The only way to get that is to confirm that you are propped correctly, then run at the various RPM points. Measure your speed, and pull the burn rate off the engine performance graph. This assumes you don't have an engine that reports fuel burn, or have actual flow meters.

 

[LeoKa]

This assumes you don't have an engine that reports fuel burn, or have actual flow meters.

Yes, this was the original point. Is there a solution on this engine for a flow meter? If yes, how is it installed?

I understand the different opinions about using the tank measuring procedure and I will do that, regardless of my future plans. At present prices, I do not have any long range plans. I just want to know approximately what my engine consumes? Preferably with a mechanical/plumbing solution. If there is none, or too expensive, I will play with the tank levels, rpms, dock and underway scenarios.

 

[twistedtree]

Yes, this was the original point. Is there a solution on this engine for a flow meter? If yes, how is it installed?

I understand the different opinions about using the tank measuring procedure and I will do that, regardless of my future plans. At present prices, I do not have any long range plans. I just want to know approximately what my engine consumes? Preferably with a mechanical/plumbing solution. If there is none, or too expensive, I will play with the tank levels, rpms, dock and underway scenarios.

You could install a Maretron metering system, but it would cost around $2k by the time you are done, so I'm guessing not something you want to pursue. I think your choices are, in order of accuracy:


1) Maretron (or similar) fuel flow metering system


2) A calibrated fuel burn tank that can accurately measure to at least 1/10th of a gallon. Unless you already have such a tank, I expect building one will be cost prohibitive.


3) Pick the fuel burn numbers off the manufacturer's data sheet.
.
.
.
10) Measuring refills of you regular tanks


You seem resistant to using the data sheets, and I don't understand why. That's infinitely easier than any of the other approaches, and I think much more accurate than (10).

 

[LeoKa]

.
10) Measuring refills of you regular tanks


You seem resistant to using the data sheets, and I don't understand why. That's infinitely easier than any of the other approaches, and I think much more accurate than (10).

No, I am not against the data sheets. They are useful. Perhaps I just want to verify with the manual method that those numbers apply correctly to my particular engine? The more info the better. I even plan to visit the local CAT dealer to see what they can find? There were helpful in the past, when I had to solve parts location issues.

 

[LeoKa]

I have done the test today. Here are the results.

Total engine run time - 3 hours and 20 minutes.
Total nautical miles sailed - 18.92
Total diesel consumed - 12 gallons.

This gives me an hourly consumption just below 4 gallons per hour. Besides the short warm up and mooring at return, the engine was running at 1600 rpm, or bit below. The weather was mostly calm, with occasional breeze in both direction. There was only one turn around, with slower rpm. Average speed was 6.2-6.7 knots.

I plan to do another later at 1800 rpm for couple hours. Curios what the consumption increase will be?

 

[Greg QS]

If you look at the fuel burn charts you can see the throttle response for this series of engine .In the low rpm range it goes up 1 gal per 100 rpm. So , 1600 to 1800 should be an additional 2 gal per hour. From 1800 to 1900 2.5 gal per hour from 1900 to to 2200 3.5gpgh more .

 

[OldDan1943]

I called the folks at Tomco, maker of American Tugs.
They sent me resulting fuel usage chart for MY boat and the conditions of the boat when taken.
Not too shabby.
The only thing that could have made it better would have been 'sea state' and wind.
They did run each test twice..... out/back .... so that's pretty close to real life.