Is Cummins the BEST Engine Choice for our Boat?

Swapping our "screaming Jimmys" Detroit Diesel 12V-71s with Cummins ISB from a 2012 Dodge Ram truck!
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[@Cheers_Warren]

Quite the challenges!!!

[@OnboardTangaroa]

Oh yes.

[@DirkDiggler-qp3vm]

Amazing wealth of knowledge

[@OnboardTangaroa]

A lot of years of all sorts of thi mashed together!😁

[@yamahagriz8820]

Thank god you married a mechanical mastermind. Could you imagine if you walked into the boat yard and asked them to do the engine refit. Thanks for sharing. Really looking forward to watching it all!

[@OnboardTangaroa]

Lol, I used to have a sign on my desk that said "evil genius". We have always realized that if we had to pay people to do this work we could never afford to own this boat. Thanks for watching!

[@hansh8071]

Looks great, the new engines must weigh less as well, good luck

[@OnboardTangaroa]

Thanks! Yes, so much less that I am looking into ballast options. Roughly 2800 lbs per engine less.

[@pilhoney10]

Don't you think a medium duty Cummins would have been a better choice? I think those 5.9 litre are a little small for that BIG boat.

[@OnboardTangaroa]

Its not necessarily about how big the boat is. Its mainly to do with how fast you want to push it. We cruise at 9 knots and max out at 12 knots. At 9 knots the boat only requires 75hp per engine. At 12 knots it only needs just around 150hp per engine. Its not a planing hull so there is no hump we have to get over therefore the torque requirement is a standard curve with speed. Torque is handled by the multiplier in the trans. With a 2:1 gearbox on the Detroits and a 3:1 gearbox on the Cummins our shaft torque is actually quite similar.

[@cornnutzgazpacho-libre3555]

Hi Blaine; The size of the two engines are quite different. I'm sure you took that all into consideration, but could you tell us the horsepower and torque comparison of the two. And the weight difference, is there going to be any trim problems. I'm sure you will love the fuel usage differences. Good video.

[@OnboardTangaroa]

The new engines should be around 400 HP and 1000 ft/lbs peak however there are some things I will be testing for aftercooling that will likely affect this negatively. The original engines have no data plates but I am thinking they are the 450hp versions and have 1200 ft/lbs of torque peak. With the reduction ratios of the new transmissions the peak prop shaft torque should be higher with the new engines. Weight difference is about 1500 lbs per engine. I am weighing options for ballasting currently. Can't wait to see how the new engines work out.

[@leop9021]

Are you going to use water cooled turbos like Cummins does on their marine engines?

[@OnboardTangaroa]

Currently using non- water cooled turbos but with water cooled manifolds. Will likely take a spare or two along with us on our travels. Thanks for watching!

[@robertwegmann1716]

Nice to see a mother and her son on a project like this

[@OnboardTangaroa]

Funny, this is the second comment we have received like this. Not sure if they are serious comments or what. Janis is my wife of 20 years. I am coming up on 50 years old and Janis is only 5 years older than I am. I guess I was just blessed with good genes?

[@markhuston9250]

Incredible knowledge, creativity and skill. Wow!

[@OnboardTangaroa]

Thank you very much!

[@deuteronimus750]

Are you going to have a bulb on the bow?

[@OnboardTangaroa]

I had debated it for a while but our cruise speed is really below the range where the greatest benefits of a bulbous bow are seen.

[@Adam-en4zm]

Looks like you're doing a superb job rebuilding those truck engines. Quite the project getting the transmissions mounted up! I'm a gasser guy, so I don't know much about diesels, but I have to wonder is going from two V12's to a pair of I6 engines that look 1/3 the weight going to deliver enough torque to keep Tangaroa underway at a good speed in inclement conditions? Those new Cummins look like they'd be more suitable in my 41' power boat than in your massive yacht (and proper engine ROOM). With electronic injection and custom tuning I'm sure you're going to get fantastic fuel economy!

[@OnboardTangaroa]

Thanks! I t has been quite an experience so far. The 14L Detroits certainly have a lot of bottom end torque however the max horesepower levels are about the same between the two engines. The 3:1 gearboxes should do the majority of the work to level the playing field as the new engines have less torque but spin 50% faster than the Detroits. Tangaroa is by no means a fast boat. Hull speed is around 13 kts. The power required to push her is not that high. The new engines by calculations will be safely below the prop curve and should have plenty of reserve to push the boat in inclement weather. These engines on a 41' boat would be designed to push it at higher planing speeds which requires lots of power that we don't need as a slower semi-displacement boat. There will likely be some prop pitch changes but they should be pretty close.

[@Adam-en4zm]

@@OnboardTangaroa Do you guys actually cruise anywhere near 13kn? That's crazy fast for a boat that size, although I've heard LOA increase = hull speed increase. My 41' can theoretically plane, but it's really a semi displacement hull and I usually keep it off plane because it drinks fuel and runs the engines hard. I also don't think it's really a true plane, it just goes nose up a bit and pushes a big wave.

[@OnboardTangaroa]

We used to cruise at 12 knots but have since dropped down to 9 knots as the boat is easier to control, more comfortable, and goes through a lot less fuel. Sounds like your boat acts like a semi-displacement for sure. Typically ours just pushes the bow down and makes a big wake. Gets a lot tougher to keep a straight line as well. Seeing as we don't currently have a working autopilot it adds a lot of excess steering.

[@ryanlambert3717]

The 12v71 has the nick name of the buzzin dozen. They sound cool in a truck but man would i hate to ride in a boat all day with 1 let alone 2. I remember hearing an old lobster boat in maine when i was a kid it was probably half a mile offshore and you could the Jimmy clear as day. Those motors leak so bad due to the design not due to lack of maintenance. For them to work as a 2 stroke they need positive pressure to fill the cylinders through holes in the sleeves, that inevitably pressurizes the crank case and gained them the additional nickname of driptroits

[@OnboardTangaroa]

I thought I had heard all the nicknames for the Detroits. Thanks! I am looking forward to hearing the new engines for sure.

[@turnerfleet3966]

detroits arnt typical 2 strokes. the crankcase is not pressurized, the engine has extra long pistons that block the holes in the liners when the piston goes above and it has a second set of rings to seal it off so there minimal blowby. they’re actually quite engines if you have the right muffler and the engine room is setup right. my 6-71 run quiet and dry. the saying if there ain’t no oil under them there ain’t to oil in them is completely wrong. the oil you see is actually soot and left over fuel pushing back in the air box and running out the weeper tubes, 4 strokes do it too they just shove it out the exhaust pipe. detroit fixed this with a catch can that was installed and emptied every so often. these are the most reliable engines out there while being good on fuel with good power. they got a bad wrap from the 53 series and people neglecting them.

[@ryanlambert3717]

@turnerfleet3966 I'm well aware of how 2 stroke diesels function. Detroits were almost all 2 stroke prior to the 6.2l, 8.2l, and 60 series. They use positive pressure to force the air through the holes in the liners and push exhaust out. When you have a motor that the cylinders are always under some level of pressure, you will eventually, due to wear and design, pressurize the crankcase higher than is normal on a diesel, and that will cause more seepage and leaks than is typical in a diesel motor. Old Detroits leaked worse than other 4 stroke diesels because they are 2 stroke more than any other reason. Poor maintenance and neglect contributed far more to a bad wrap for sticking injectors and dangerous runaway motors.

[@chriswoodward5368]

I wish hade seen this sooner as it explains a lot. Glad to see your explanations of what it’s like to try and do a re-power. Everybody thinks that you just take one engine out and drop the other one in. Even if you’re buying a package from Cummins or Cat with the transmission and everything it’s still not simple. I’m going to show my age. electronic engine would’ve not been my choice. That does not mean it’s not the right choice for you. I have a great dislike for anything electronic. The complexity and the cost of repair is more than I can stand. As a former truck mechanic, I watched trucks become less reliable every time they add a new layer of electronic complexity. I believe KISS System. I will be interested to see how this does on sea trials. My choice for engines would’ve been a cat C9 or an ISL 9. That does not mean that your choice was incorrect. Great video I look forward to the rest of them.

[@OnboardTangaroa]

You may just have a little catch up to do on the videos 😁. Yes, repowers are never easy and I chose probably the most difficult way to do it however I should end up with a more robust and better integrated result. I totally understand the mistrust of electronics. I am very capable with the new electronic control systems and it took me a bit to get comfortable with the idea. The benefits are just too tempting. While I do dislike the cost of the new electronic parts I am not uncomfortable with the complexity. It is I have been doing for a long time at this point and I actually enjoy it. With the control units I am running diagnosing is considerably easier as well. The C9 of ISL9 certainly would have been fantastic choices but I reckon that would have cost me well over double what I have into these and definitely would not have been in the budget. I am confident these will work well but only time will tell. Take care!

[@pilhoney10]

I'm sure you'll get a good price for those Detroit's.

[@OnboardTangaroa]

Hopefully we can sell them. No bites yet.

[@johnvcramer5517]

Those Detroit engines should be a better fit. although a smaller Detroit like a 6V 92 or a 8V92 could work to.!!

[@OnboardTangaroa]

The 92 series could for sure but still not quite what we were after. Owning a performance automotive shop where we specialize in new engines and engine management I coudn't see myself going with an older motor and even the 92 series design is older than I would like. Definitely not against them. Just not quite what we were looking for.

[@JustinTurnerman]

Are you keeping the stock hp and torque or are you doing some performance modifications.

[@OnboardTangaroa]

We are keeping it pretty mild for power but the injectors are a higher flow than the stock truck injectors and the camshaft has been swapped for a Colt Cams stage 2 cam which will help with EGTs and economy. The turbo is a Borg Warner S366 which is a mild upgrade as well.

[@JustinTurnerman]

@OnboardTangaroa awesome can't wait to see it installed. I'm sure fuel economy for your trip is more important then speed anyways.

[@OnboardTangaroa]

Lol, oh yes!

[@robertharris1016]

Detroit's are also called bird scarers!

[@OnboardTangaroa]

Seems fitting. Thanks for watching!

[@turnerfleet3966]

the leaking with those engines are greatly exaggerated. all those covers are for service use and for additional accessories like air compressors and hydraulic pumps. as long as you don’t touch the covers and blocker plates which you should have no reason to your good. the air box doors sometimes need new gaskets which are cheap or can be made easily. the oil issue from these engines is from the weeper tubes which let soot and excess fuel that comes from idling and no load conditions (happens to every engine) that was blown into the air box out, a simple catch can with a small filter will fix that. another big issue is ventilation, all engines sweat or have blow by if some sort, to fix it with any engine you need proper airflow to get the oil out before it lands. they are actually rather quiet compared to other engines you just need to set them up right, volvos, cats, cummins are all equally loud if not louder especially the cummins (they shake the boat apart). probably the best thing for you guys to do would have been to put 6-71t in there since they are mechanical engines which can’t have any electrical issues and will run as long as they have fuel and air. if you really want electronic control it is very easy to switch to a ddec (detroit diesel electronic control) that allows you to have the ability to do some tuning for better efficiency. my 6-71na running n70 injectors at 1500rpm will burn about one and a bit of a 5 gallon jerry for a 6 hour round trip (60km) and that was a tired old work tug which is setup for pushing and not for on the run. my engine is actually rather dry but it needs some tlc since it was abandoned for 20 years until i got it going. if your looking for reliability go for mechanical everything, the transmissions it has are way more reliable than the electronic control, the cables just need oil. it would be cool to see those old detroit’s make their way all the way across. gm certainly did something right to make the same engine from ww2 all the way up till the 90s.

[@OnboardTangaroa]

I have to say, I don't dislike the Detroits. The run well and as you said will run until they run out of fuel. These particular engines are leaking oil from many places, not just the weeper tubes. I added the late model valve covers with breathers when we first bought the boat to help it breathe a bit. Back then my intention was to modify these engines with some modern components to increase efficiency. The problem we the motors we have is that there are no hour meters or service records. To go on the trip we are planning I would at the very least want to rebuild them for peace of mind. Unfortunately, no matter how well I rebuild them it will not fix the fact that their BSFC is tragic compared to a modern 4 stroke electronic turbo diesel. They also do not like to be run at the engine speeds we would normally cruise at. A 6-71T would be better as it would be a tad more efficient but we would still have had to change the ratios in the gearboxes. Even with that the fuel consumption would still be upwards of 25 percent worse than a modern 4 stroke turbodiesel. That's a lot of lost range. As for the noise, even if they were as quiet as you claim (standing in my engine room underway I would tend to disagree with) you are comparing them to similar displacement/era engines. The new common rail Cummins motors are incredibly quiet due to the ability of common rail injection to use a pilot injector pulse to quiet if not eliminate the diesel rattle and they are incredibly smooth running as the inline six motors are inherently well balanced. Unfortunately with the reliability of an engine designed during WW2 come the drawbacks associated with said old design. There is a reason they stopped making them 20+ years ago. The only part of the transmissions themselves that are electronic are the solenoids and they have manual back up in case of failure. That being siad electronics have come a long way over the last 40 years. They are not the unreliable systems they were back in the 80's. I have been working with them for close to 30 years in one way or another and have no fear of them. Treated right the modern Cummins marine diesels have tbo times rivaling or exceeding the Detroits. Sure, I could rebuild the Detroits in frame but I doubt I will still have the boat at that point. Thanks for watching and as I said I don't hate the Detroits, they are just not the ideal engine for our purposes.

[@codew5y2f94]

Will both engines have the same rotation? If so how will the boat not crab to one side?

[@OnboardTangaroa]

Both engines have he same rotation but he transmissions are capable of full power and speed in either direction. To run counter rotating propellers you just run the other transmission in the opposite direction. Easy peasy.

[@imoovabull6042]

final drive reverses the rotation to prop

[@hildablanco1591]

You can't remove the piston sleeves in the Cummins only in the 2 strock Detroit's and a 8 .2 Cummins is better than the 6.7

[@OnboardTangaroa]

Yes, as I built these engines I definitely know they are not sleeved. I think in one video I may have gotten tongue tied when I said which engines had sleeves but if I did it was not intentional.

[@va7dgp]

I blew my head on my cummins in my big truck. Granted it was back in 2003. I had to run my heater blowers and fan in my truck as I was climbing that mountain west of Colorado.

[@OnboardTangaroa]

There were head gasket issues on some of these motors from what I have read. When I built these I o-ringed the block and am using upgraded head studs as well. It should not be a problem. Thanks for watching!

[@scottburke9379]

You want to see a boat build ,go to Colonial heights va and see

[@OnboardTangaroa]

I had a google look. If i saw what I think you are referring to that is something else!

[@scottburke9379]

It's stainless steel .

[@OnboardTangaroa]

:o

[@joesutherland225]

5.9 12v would have been a better choice far more dependable better fuel consumption too electronics equals problems just ask any dodge Cummins owner after the 5.9 .oh Cummins leak too

[@OnboardTangaroa]

We will have to agree to disagree on this one. The reduction in fuel economy on the 6.7 engines was to do predominately with the need to meet emissions requirements which I am not near as constrained by in this application. I may be mistaken but I believe the marine 6.7 motor specs actually show less fuel consumption than the marine 5.9 engines. As far as the electronics, yes it is an additional point of failure and one that I have much debated. That being said, the marine QSB 6.7 engines have a pretty amazing track record. Yes, I do realize the Cummins engines will leak at some point. Every engine will but it is better than something that is at best designed to leak a little.

[@joesutherland225]

@@OnboardTangaroa yeah though those Detroits are a very good motor they are leaky buggers your point about emissions is well taken still a pain in the butt todiagnose fueling hiccups compared to mechanical injection of the 5.9 it's the old Cummins fan argument over this lol

[@OnboardTangaroa]

Absolutely, everyone goes with what engines they like and are comfortable with. I have been doing electronic fuel injection for a very long time so am very comfortable with it. With the ecu's I am using I have all the information to diagnose at my fingertips. Will also be adding per cylinder EGT monitoring to assist in diagnosing individual cylinder problems.

[@MrAmartin8]

Who would have thought it ?? Turning a boat into a car ??? The old Detroits were very reliable and didn't leak if they were built right . The only other area to leak is the air box drains which can be contained . And they can be rebuilt in place . I know this because I was a marine mechanic in the 70's working only on Detroits . Your choice on what you want to use in your build but seems to me you are spending alot of money to change something that has been proven over the years . Just saying ...

[@OnboardTangaroa]

I did say in the video that the Detroits were very reliable. I am certainly not knocking that fact. As for the leaks, any engine can be built to be dry for a time. The leaking was only one of the issues I have with the Detroits. The fuel consumption is one of the bigger issues. There is close to a 25% reduction in fuel burn with the new engines. That is obviously directly proportional to range and there could be times where we could really use the additional range. Fifty years of technological advancements go a long way. A bit more explanation may be warranted. When we bought Tangaroa there was an obvious lack of maintenance. There are no hour meters on the current engines and zero maintenance history. As a technician I would NEVER trust these engines as is to do the traveling we plan to do without said history. At the very least I would want to do an overhaul. The expense to do a complete overhaul would not be trivial even with myself doing all of the work. At the end of the day the benefits of going to he new engines is worth the additional expense for us. Sure, there will be different demons to face with the new engines but I am ok with that.

[@MsJon52]

@@OnboardTangaroa love the old engines, but totaly agree with your resoning, going on long sea journeys you got to trust the engines, if you build them and test them yourself it should give you the much needed confidance in them, plus the fuel saving, lol

[@OnboardTangaroa]

Peace of mind is very important with a trip like the one we are planning. Everything doesn't have to be perfect but the Mechanicals have to be pretty spot on for me to be happy. Thanks for watching!

[@buckrager4165]

Should have bought the ISX engine those 6.7 l engines are just not built for what your doing

[@OnboardTangaroa]

I respectfully disagree. They are a perfect fit for our application. What is it you feel they lack in for our use?

[@buckrager4165]

@@OnboardTangaroa I have to maintain a school bus fleet with these 6.7 Cummins engines and I’m seeing blown or worn out engines at 135,000 to 140,000 miles I’m sorry in my opinion they are a light duty engine we had buses with older pre emissions DT466 engines and they were a lot more reliable

[@OnboardTangaroa]

Very different loads and uses on a bus fleet compared to a semi-displacement boat. In our application these engines will see 1600-1800 rpm and 60hp for 99%of their lives with little idling. They are also not loaded with all of the emissions equipment that the road going engines are a slave to.