Doug's Re-power

Post by **dougl33** » Sat Oct 28, 2006 9:10 am

I've decided to re-power with a pair of RTO 6BTA's this winter. They are 300hp and are coming with brand new ZF 220A 1.5:1 gears. Some of you have known this for quite some time and I appreciate your keeping it quiet while I worked things out. The work is being done at my yacht club by the Cummins rep for my area, Doug Currier of Russ Marine in Peabody, MA. I will be keeping my inch and 3/8's shafts. The port engine and the genny are already out. If anyone's interested in the mains (1300 hours with 1.9:1 BW gears), genny (6.5 kw Onan w/ 300+ hours), and/or the twin scan flo-scans please let me know. I am looking for $4500 for the motors, trans, and flo-scans and $1500 for the gennie. I also will need to sell my 2004 4 blade Michigan Nibral DQX 20x16 props. The have a very small cup. I am looking for $1500 for these as well. If some from the site buys everything, I will sell it all for $7000. Regards, Doug L. 1986 33 Bertram FBC Queen Elizabeth Marblehead, MA [img]http://www.bertram33.com/photogallery/p ... sabeth.jpg[/img]

jav · Post by **jav** » Sat Oct 28, 2006 2:00 pm

Doug, congratulations! I don't think you'll regret the decision. Just a quick question though.. did you consider 1:5 gears versus the 2:1 or were they only option?

Post by **dougl33** » Sun Oct 29, 2006 3:17 am

John, I'm looking to keep my original shaft size and trying to utilize my 3 blade 21x20 props (I'll be getting them re-pitched up to 22's). Regards, Doug L. 1986 33 Bertram FBC Queen Elizabeth Marblehead, MA [img]http://www.bertram33.com/photogallery/p ... sabeth.jpg[/img]

jav · Post by **jav** » Sun Oct 29, 2006 11:40 am

Doug, thats kind of why I asked.... I had a similar decision when I did my RTO engines since the gears had to be new. Please don't take this the wrong way...no disrespect intended. it's just that I had the option of any ratio - with no cost impact, and I didn't research it as well as I should have back then. I'm just trying to help you if I can. I took the liberty to run some quick calcs on your boat. I used (24000 pounds loaded and ran both the average and slow planning hull forms)... IMHO, the 1.5:1 appeared to be a better option. I think the 6BTA 300's are 2800 RPM engines? Using the 2:1 gears as your planning.. it put prop pitch above 30" which is a non standard (Michigan stops at 28 for 21" diameter props). I don't think the 22 pitch will work. Also, the 2:1 puts more torque on your shafts than the 1.5's would. Anyway, just food for thought and if I can be of any help, don't hesitate to ask.

Post by **dougl33** » Sun Oct 29, 2006 12:39 pm

John, None taken. After going back and looking in my notes, we will indeed be using 1.5:1 ZF 220A's. I've played around with the prop calculators on boat diesel as well. In my attempts to establish a base line with a known quantity (my gas engines and gears), I actually had to use a fast planing hull with a weight of 27.5K lbs, 300hp, a 2:1 ratio, and 20 inch 4 blade props to hit what I got with my gassers: Max Speed: 26.9 kts Cruising Speed: 18.6 kts Fuel: 16 US Gall/Hr PROPELLER BASED ON INPUT DIAMETER Diameter: 20.0 Pitch: 17.1 Blades: 4 Its what the calculator is giving me for cruise speed, fuel burn, and prop size that makes me think that this is the best fit. Regards, Doug L. 1986 33 Bertram FBC Queen Elizabeth Marblehead, MA [img]http://www.bertram33.com/photogallery/p ... sabeth.jpg[/img]

IRGuy · Post by **IRGuy** » Sun Oct 29, 2006 1:17 pm

My '83 FBC has Cummins 1996 6Bt's 315 HP, and runs at 23 knots at 2,400 RPM. The 315 HP 6Bs are indeed 2,800 RPM engines, which should not be cruised at more than 2,600 RPM, and Tony Athens said I should run them at no more than 2,400 RPM for them and consequently me, to be happy. I have Twin Disc 5050 gears, 1.5 to 1, and 21D x 23P 3 blade no cup wheels. I believe the 300 HP 6Bs are essentially the same as the 315 HP with perhaps some different bolt on items. I don't have enough time with them yet to have good fuel burn numbers. You will be happy with the 6B's, and I can tell you, there is enough room to work on them in my FBC. Not a lot, but you can get outboard of them if you don't mind being squeezed here and there. Frank B - IRGuy@aol.com "Phoenix" 1983 FBC Wilmington, NC

Post by **dougl33** » Sun Oct 29, 2006 1:47 pm

Frank, Doug Currier actually told me that the 300's and 330's were really the same engine just that Cummins changed the way they rated the hp. If that's true then I'd bet that your 315's are probably the same as the 330's as well. What are you getting for WOT? Regards, Doug L. 1986 33 Bertram FBC Queen Elizabeth Marblehead, MA [img]http://www.bertram33.com/photogallery/p ... sabeth.jpg[/img]

Rick · Post by **Rick** » Sun Oct 29, 2006 2:06 pm

Congrats Doug ! I bet you won't miss those Merc's for a micro second. Doug does good work and seems to know Bertram wiring very well, so the transition should go very smooth. Let us know if you need any help and best of luck. Rick Ticket 85 SF Falmouth, MA

Post by **dougl33** » Sun Oct 29, 2006 2:09 pm

Thanks Rick. I might take you up on that when it comes time to paint the bilges. Regards, Doug L. 1986 33 Bertram FBC Queen Elizabeth Marblehead, MA [img]http://www.bertram33.com/photogallery/p ... sabeth.jpg[/img]

Rick · Post by **Rick** » Sun Oct 29, 2006 2:13 pm

Hey I'll pass a beer down to you no problem ! Rick Ticket 85 SF Falmouth, MA

jav · Post by **jav** » Sun Oct 29, 2006 2:35 pm

Doug, that makes me feel better! I didn't want come off as raining on your parade or a know it all but having stepped in that pot hole myself, I was hoping I could coax you to dig a little deaper. I'm glad you already had it in hand. I think you'll be tickeled pink with that setup in the end. I also like the 3 blade choice... I've been dying to try the new DJX series (I like the DQX series too but DJX is just such a sweet compromise between the speed of 3 blade and blade area of a 4 blade) Doug/Frank- I've struggled with some of the Cummins nominclature in the past. If you go to the Cummins data base on Boatdiesel, you won't find a 330 HP or 300 HP engine at all. Cummins of late has had a funny way of naming engines. What Cummins calls the "330B", is not a 330 HP engine. It's actually rated at 315 HP. The same thing happens with the 370B in that it's often refered to as 370 HP engine when in fact it's really rated at 355 HP. Doug, the closest engine they list to 300HP is the 6BTA5-9M-SW which is essentially the 330b, detuned for medium continuous duty at 280 HP (light commercial service)... For all intents and purposes, my understanding is that engine is as bullet proof as they come. It can be run proportionally harder than the 315 HP version, which gives it almost identical cruising speed and just a little off the top where you wouldn't run it any way. Either version would be a great find and I'm jealous. Please keep us posted so we can live vicariously through you.

lobsta1 · Post by **lobsta1** » Sun Oct 29, 2006 2:37 pm

Rick, Since Doug is a two-fisted beer drinker, I would pass down the second beer to him. Except he needs one hand for painting. Al P.S. Doug, Congratulations on making the repower happen! 1978 33 FBC NITES OFF

Capt. Ed · Post by **Capt. Ed** » Mon Oct 30, 2006 2:13 am

Way to go Doug, nice choice in your set-up!

franklyprice · Post by **franklyprice** » Mon Oct 30, 2006 2:46 am

Doug, Glad you finally came out of the closet(so to speak)

IRGuy · Post by **IRGuy** » Mon Oct 30, 2006 2:51 am

During the seatrials with a supposedly clean bottom we got 2920 and 2930 rpm, and I believe about 27/28 knots. I agree they are all probably the same engine, possibly with some external component differences. I believe I read somewhere that they "uprated" the 315 HP version to 330 HP by simply increasing the rated max operating RPM from 2800 (for the 315 HP) to 3000 (for the 330 HP). In fact, I have a graph of HP and torque vs RPMs for the 315/330 engines, and the output lines are identical for both, except the 330 line goes to 3000 RPM. It does not make sense to have many differences in engines with ratings so close together. I would suspect the 370 HP's have different fuel pumps and injectors at least. I am as confused as everyone else seems to be about the ratings.. there are at least three Cummins categories for ratings based on operating conditions.. they are "Recreational/Light Duty Commercial", "Medium Continuous", and "Continuous". I have the Cummins O and M Manual in front of me but I won't take the space here to define each, other than to say they are based on combinations of the fraction of operating time that engines are run at full power, the number of operating hours per year, and the max operating speed. Doug.. I would suggest that you get a manual ASAP, because there is a ton of info available there. I bought one from my local Cummins guy for about $35 as I recall. I believe my 1996 engines were RTO's from a new large custom sportfish that the owner repowered after one year because he wanted more speed. Apparently while he was using them in the first year he had Cummins make several trips to his boat and make some adjustments. As a result the Cummins warranty work computer database states Cummins "derated the engines" to 250 HP, supposedly by modifying the fuel pump. I suspect what Cummins was trying to do was to say the boat they were installed in really needed "Medium Continuous" duty rated engines instead of "Recreational/Light Duty" rated engines, and therefore these engines if left in the boat should be considered 250 HP instead of 315 HP. This is usually accomplished by reducing the max RPM of the engines. There is some suspicion that this was really a paperwork shuffle by Cummins to convince the owner he needed larger engines based on the size of the boat and the way he wanted to use it. As far as anyone can tell my engines perform as 315 HPs would be expected to perform in the B33 FBC, and the nameplate data was never changed, so I am not concerned, except when I sell the boat I will have to convince the buyer in fact they really are 315 HP if he pulls the Cummins files as I did. I have recently gone through the complete raw water system on my port engine and I can say they are fairly easy to work on in an FBC.. and per Sean's comments they should be great to work on in a SF with engine boxes. Everyone I have spoken with who knows these engines says they are pretty much bulletproof. I feel with my setup of engines, gears and wheels I can run at the speed I hoped for (at least 22-23 knots) while not overloading or overrevving the engines (2400 RPM), and have another 200 RPM in reserve if I need to get back a little faster. These engines are rated at 2800 max, and should not be cruised at over 2600 RPM, and I plan on running them at 2400 RPM max since I am a conservative engineer who is a diesel newbie. Frank B - IRGuy@aol.com "Phoenix" 1983 FBC Wilmington, NC