Old iron is out!!!!!!!

[harnett]

I did rework the cockpit. Mezzanine seating, bigger deck hatches and ER access from the cockpit. This did require moving the rear fuel tank aft. There are some pictures posted.
The current plan for gears are ZF325A with 1.73:1 ratio with 28' 4 blade props. Still working through the pitch. The M3 rated John Deere's make 500 HP at 2000 RPM. A software change is available to upgrade to an M4 rating making 575 HP at at 2100 RPM. Now for my black magic estimates. I have some test data from Cummins engineering of a 53C with QSM11. She ran 20 knots at 1800 RPM and the QSM is making 320 HP here. Per side of course. This is per Cummins engineering. I have additional data from another 53C owner with QSM's that match that. So if I used that to estimate the JD is making 320 HP prop HP at 1800 RPM and about the same torque as the Cummins. I don't know if my QSM numbers are crank or prop HP but I'm thinking I should be close to 19 or 20 knot cruise with the JD. Maybe just a bit lower cruise since JD wants me cruising at 50% load. That would technically be 64% but the Deere torque curve is really flat through here making tons of torque down to 1400 RPM before falling off. The 500 HP JD makes more torque than the 670 HP QSM by just a bit at 1800 but at 1400 it's over 10% more.. We are back at that displacement thing but torque turns the prop. So that's how I got here, big displacement, low HP and high torque I hope will equal a lightly loaded happy engine. FYI the JD is basically the same displacement as the 12V71N that it's replacing. 13.5 vs 13.96. Make about the same HP at 300 less RPM. Can't find a torque spec so not sure of that but at 3500 lbs lighter there is just not way I won't get a slight bump in performance with all the other benefits of a modern engine. Well that's the plan anyway. We all know how the best laid plans work out sometimes.

 

[jim rosenthal]

FWIW I think you are right. I suspect your boat will go a bit faster, use probably 60% of the fuel that it used to use, and generally run cleaner and be easier to maintain.

 

[Cricket]

So just thinking this through since i've already been down this road with a similar boat.
If it was me i would go for the higher horse power rating of 575hp, and then run them slow to cruise the 20 knots you're looking for. Is there a big cost increase to the JD 650hp and 750hp models?
Looks to me the JD is more like a CAT c15/3406E than the QSM as QSM only has 661 CID, CAT 893 CID, JD 824 CID with the CAT pumping out 850 hp compared to the JD's top rating @ 750hp, so JD is already being conservative.
I'm a big believer in high horsepower run at moderate RPMs for longevity and fuel savings. There's a reason the charter boat fleet gets so many hours on a 2300 RPM engine they cruise at 1600 RPMs, as an example.

There's 2 projects we should have done, move the aft tank back to be able to get the ER access through the cockpit and not making the bridge wider and also pushing the bridge front forward.
Extending the aft bridge floor ended up being one of our best improvements.
What we ended up with is using what was the generator hatch in front of the door for access moving the genset to the other outboard side, worked out pretty well with the Amtico flooring in front of the door area.

 

[harnett]

I don't disagree. I bought the AF version which means no seawater cooled aftercooler. The SF version has a saltwater cooled after cooler and goes to the higher HP. I am limited to the 575 HP. Its a simple software upgrade they do. Well plus paying them a few more grand to do it. It also changes to engine to an M4 rating. I'm holding it in my back pocket til I see how things shake out. It I need the extra HP it easily available to bump from 500 to 575.

I think you are right. It is closer to the C15. JD is just very conservative in the ratings.

 

[jim rosenthal]

The last 53C I know of with a QSM11 repower was Hookshot, done by Slane Marine. I think her M11s were rated at 700hp. She topped out at >28knots on her sea trisals; this included the weight savings of the Cummins engines, and the bigger bridge fitted by Slane, and some other mods. Very good speed for a relatively small engine in that heavy big hull.

I don't think you'll have trouble cruising 20 knots. How much faster she'll go is an open question.

 

[Cricket]

I definitely get going with the freshwater cooled after cooler, just removes a major potential issue.
Think it's going to be a wash cost wise for the upgrade to 575hp and then have to modify/mess with the props etc. Would that be "more is less" ??????? Looking forward to watching your project.

 

[harnett]

That's a good point. I'll have to rethink that a bit. Might just should start out with the 575 hp.

 

[Westfield 11]

Are the new motors 3500 lbs lighter on each side? If so, what effect will the removal of that weight have on seaworthiness and stability? When I was considering a 61’ cpmy with the DD’s replaced with Cummins, the consensus here was that I needed an NA to run stability calculations for safety’s sake. Does that not also apply here? If not then why not?

 

[harnett]

The 3500 lbs is total not per side. The JD pair is about 1000 lbs heavier than a pair of Cummins. The 3500 Lbs is about a 5% weight reduction in my boat. The other thing is that by going to a 7 degree gear box the engines will sit lower in the hull than the Detriots did. I don't believe the weight difference will matter especially when coupled with sitting them lower in the hull. I'm certianly hoping that is true. With so many boats out there with Cummins running I think if it made a big difference we'd have heard about it by now. I haven't ran the calculations but I feel certian that the change in weight will have much less effect on stability than say a full tuna tower.

 

[jim rosenthal]

I don't think you will have a stability problem at all. You could get a NA to look at it, but frankly the money would be better spent on the install. You might find you have to move some things around. You would think that putting in engines which are the same amount lighter on each side would not cause the boat to list, but I have heard of it happening. I have no idea why.

The JDs are very good engines. Lugger used to use them in some applications; they were very strong and reliable.

 

[Texastailboard]

Really looking to see how your project turns out, we have been considering a repower on our 52. Just haven’t finished our cosmetic stuff we have currently started on.

 

[krush]

.. Maybe just a bit lower cruise since JD wants me cruising at 50% load. That would technically be 64% but the Deere torque curve is really flat through here making tons of torque down to 1400 RPM before falling off. The 500 HP JD makes more torque than the 670 HP QSM by just a bit at 1800 but at 1400 it's over 10% more.. We are back at that displacement thing but torque turns the prop. So that's how I got here, big displacement, low HP and high torque I hope will equal a lightly loaded happy engine. FYI the JD is basically the same displacement as the 12V71N that it's replacing. 13.5 vs 13.96. Make about the same HP at 300 less RPM. Can't find a torque spec so not sure of that but at 3500 lbs lighter there is just not way I won't get a slight bump in performance with all the other benefits of a modern engine. Well that's the plan anyway. We all know how the best laid plans work out sometimes.

If you toss out the torque thoughts and data and do your analysis with HP only you will come to much more clear conclusion. The torque does not matter...and that is exactly the reason you can't find a torque curve for the old detroits.

The engine makers provide a HP vs RPM curve that shows you what rated HP the engine can reliably make at a given RPM. However, in a boat application with a fixed propeller, the prop demand curve will likely never line up with the engine HP curve (prop is exponential, engine is mostly linear). Cummins marine usually provides a generic "prop demand curve" on their engine plots to give you an idea what the HP vs RPM output will be in a generic boat.

Prop size/pitch will shift that prop demand curve around. The usual goal is to have the prop demand HP be equal tot he engine HP output at rated RPM. However, there are unique cases where somebody may "overprop" to increase cruise efficiency (see this thread (wow, it's been over 10 years since that discussion!): https://www.samsmarine.com/forums/s...And-Engine-Life-When-Running-Big-Engines-Slow)

 

[nautibake]

The 3500 lbs is total not per side. The JD pair is about 1000 lbs heavier than a pair of Cummins. The 3500 Lbs is about a 5% weight reduction in my boat. The other thing is that by going to a 7 degree gear box the engines will sit lower in the hull than the Detriots did. I don't believe the weight difference will matter especially when coupled with sitting them lower in the hull. I'm certianly hoping that is true. With so many boats out there with Cummins running I think if it made a big difference we'd have heard about it by now. I haven't ran the calculations but I feel certian that the change in weight will have much less effect on stability than say a full tuna tower.

I'm finding a great deal of inspiration from your project (have to admit, also a welcome distraction from watching Dorian). I grew up driving a 1958 JD tractor pulling hay mower, hay bailer and 5-ton hay wagon. I have imagined a repower to CAT or Cummins but for some reason never even considered the Deere. I have a 1977 Hatt 58 MY. Although I don't like to admit it, I primarily cruise with a trawler profile like many here. Do you think the M2 or M3 version of your engine would be a good match? I cannot get close to getting on plane with my current DD 8V71TI's. 2400 lbs of gyro stabilizers and an 850 lb tender all basically on the stern I assume are the main reasons. I would like the option of occasionally getting up to 18 - 20 knots to get somewhere (or to get away from something). I know many more details would need to be analyzed, but just curious if you thought these would fit the profile for a 58MY.

Also, without disclosing anything specific, do you mind sharing approximately what the street price is to buy those engines? And the ZF gears?

In any case, look forward to seeing your progress, and good luck!

 

[harnett]

Interesting that you said that. I grew up sitting on a JD tractor in the fields to so there was definitely some history with JD there. I know of at least one 53MY with JD 8 liters running around. The owner has nothing but positive things to say about them and he says she runs on plane great. I can only imagine with the 13.5 liters a 58 would fly. As for price they were a bit more that Cummins recons but more or less the same as the Cat C12. I'm going to keep everyone post but it's going to be a bit longer than I thought. I didn't order my engines until I had the old ones out and had test fit a CNC template I made. I was really worried about the oil pan hitting the hull. All my measurements said it was ok but I was to scared to place the order until I knew. The order is in but they are telling me I may not see them until Nov. 12V is a stock item but 24V that I wanted is special order and takes a bit longer. Not that I don't have lots of engine room cleaning and preping to do anyway. Still hoping for a 2019 launch. We'll see.

 

[nautibake]

Interesting that you said that. I grew up sitting on a JD tractor in the fields to so there was definitely some history with JD there. I know of at least one 53MY with JD 8 liters running around. The owner has nothing but positive things to say about them and he says she runs on plane great. I can only imagine with the 13.5 liters a 58 would fly. As for price they were a bit more that Cummins recons but more or less the same as the Cat C12. I'm going to keep everyone post but it's going to be a bit longer than I thought. I didn't order my engines until I had the old ones out and had test fit a CNC template I made. I was really worried about the oil pan hitting the hull. All my measurements said it was ok but I was to scared to place the order until I knew. The order is in but they are telling me I may not see them until Nov. 12V is a stock item but 24V that I wanted is special order and takes a bit longer. Not that I don't have lots of engine room cleaning and preping to do anyway. Still hoping for a 2019 launch. We'll see.

Thanks harnett, good luck getting your engines in and installed. Really looking forward to your progress. it’s hard to believe those engines will make that much HP on such low fuel flows, but wow that would be amazing. I won’t have any issues with space.

 

[Rocco]

Did the 24v JDs show up in November as promised? Curious how the project is going.

 

[harnett]

No they are a little behind. Production date got changed to Dec. 7th. I am pretty much ready with everything else waiting on the engines to arrive. I'll keep everyone posted.