This forum contains 22 topics and 99 replies, and was last updated by  Stephen Oliver 2 days ago.

Viewing 20 topics - 1 through 20 (of 22 total)
    • Cummins Marine Forum Topics
    • Repower Question

      This topic has 4 replies, has 4 voices, and was last updated by Stephen Oliver 2 days ago

      August 10, 2018 at 10:03 am I’m a new registered user, and I’d like to ask you a few questions and hopefully anyone can be of some help. sbmar website is great btw. I am interested in a purchase of a 1998 Maxum 4100 SCB, but it has 330hp Cummins 6BTA’s, and I think that is not enough engine for that weight boat. I could be wrong, but while I know some may say buy an express boat if you want something that does around 22knots, but I am leaning towards a Se…

      Started by:  Carmen L Spagnolo


      4 Replies
      Reply #4 August 13, 2018 at 10:40 pm Are they 330’s I just had a quick look and most I could find are 370? There was also an Aussie review of the boat with 370hp’s and they reckon close to 30knts top speed and 22-24 cruise.. so doesnt seem too under powered. As a comparison I have a 40 (45ft overall) locally built flybridge weighing in at arounds 11,5 metric tons so similar weight, with a higher (18deg) deadrise and narrower beam by around 1ft – so in theory mine…

      Last Post by:  Stephen Oliver posted: 2 days ago

    • Re-Powering 1999 26' Shamrock Express

      This topic has 4 replies, has 3 voices, and was last updated by john 1 month ago

      July 9, 2018 at 10:29 am Hi from the East Cost, I have been considering to re-power the 99 shamrock 26′ express from the 5.7 gas Sea max for long time to power Diesel to get more fuel efficiency per Gal and long range . what is the right eng application or the right fit for this 99 26′ Express. Is Cummins like 6BT 215hp~250hp with the current ZF to keep the existing 1 1/4 shaft will be the right fit for this project ? what is the cost associated with …

      Started by:  Al


      4 Replies
      Reply #4 July 10, 2018 at 5:30 pm I have a friend that has that has that same boat with a cummins 6b 210. They came as a option. To me putting a diesel in a boat like this is a great project. Is it always the right choice?? Going from gas to diesel requires a lot of work. Some of these boats with a diesel in it might be a better way to go. Not trying to burst your bubble just putting it in perspective. I would do a little research and there is a owners club with a ton of info.

      Last Post by:  john posted: 1 month ago

    • Unspported Shaft Length

      This topic has 1 reply, has 2 voices, and was last updated by Tony Athens 2 months ago

      May 19, 2018 at 9:01 pm Hell Tony and All, I’m considering a repower of a fiberglass keel boat. My calculations show a 28″ to 30″ length of shaft between the hull shaft log forward to the shaft/tranny coupler. Figure 380 QSB 5.9 Recon power, 8 degree ZF85A gear, 2:1 gear swinging a 22X19 four blade more or less. TBD . Prop shaft diameter 1.75 inch. 20/40 rule apply here ? No less than 20 X shaft diameter between bearings? = 35″ No more tha…

      Started by:  Bill Desmarais


      1 Replies
      Reply #1 May 20, 2018 at 1:46 pm Am missing total shaft length? Flexible or rigid engine mounts? Flexible or rigid shaft seal/log? Tony Tony Athens Seaboard Founder Go here for the latest stuff we put together and share for all to see: https://www.sbmar.com/tonys-tips/

      Last Post by:  Tony Athens posted: 2 months ago

    • Transmission Clearance to Hull

      This topic has 2 replies, has 2 voices, and was last updated by Mike P 3 months ago

      May 12, 2018 at 8:10 pm I am currently in the middle of a repower project. In order to get good shaft alignment, I need to have the engine sitting low in the boat, with the corner of the ZF220A only clearing the bottom of the boat by about 3/8″ on the outboard side. Is this too close? Is there a rule of thumb or a standard for this? Appreciate any input. -Mike-

      Started by:  Mike P


      2 Replies
      Reply #2 May 14, 2018 at 9:01 pm Tony, A fiberglass boat, a 37′ SeaRay. The stringers looked wimpy to me so I added 3/4″ of plywood that was glassed in, transom to forward engine room bulkhead. Mounts are 1/2″ aluminum “L” channel with 1/2″ backing to sandwich the top of the stringers, each bracket being 12″ long. I used new Barry mounts I got from Cummins. Sorry, no pictures, my phone dropped and ceased working today!

      Last Post by:  Mike P posted: 3 months ago

    • 1997 Bertram 36 Repower

      This topic has 13 replies, has 8 voices, and was last updated by Tim Schantz 3 months ago

      December 27, 2017 at 3:03 pm We are considering a purchase of a 1997 Bertram 36 with Cummins 450 Diamond engines. Approximately 1800 hours. Engines appear to be in good shape (sea trial and inspection pending), but the current owner has told us its not very fuel efficient above 1800 RPMs. Displacement is 30,000 lbs dry. Owner says at 1850 RPMs it is 17 knots and ~24 GPH, which seems a bit higher than the published power curves for the 450C Fuel efficiency, no smoke/fume…

      Started by:  Tim Flynn


      13 Replies
      Reply #13 May 2, 2018 at 8:12 am I’m a little late to the party here by the looks of it! I figured I would chime in anyway . I just completed a repower of my 36 Bertram Moppie. The boat originally had 430hp Volvos in it. I repowered with a set of 550hp QSB6.7’s. From my experience your fuel burn numbers at 1800 don’t seem too far off. This hull does not like speeds below 20 knots, it’s like it is fighting itself to plane out. With the Volvo’…

      Last Post by:  Tim Schantz posted: 3 months ago

    • Possible shamrock repower

      This topic has 1 reply, has 2 voices, and was last updated by Tony Athens 3 months ago

      March 21, 2018 at 8:50 am Thinking about repowering a 1987 26 shamrock stalker. Boat weighs about 6000 lbs dry currently with a pleasure craftt 350 gas direct drive inboard. Boat will be used mostly in Arkansas but trailered to coast for some “real” fishing and diving adventures. Currently has 54 gal port and starboard fuel tanks total 108 with about 100 gal usable. I would like to increase speed thinking of around 350 to 380 hp Cummins 6bta? Currentl…

      Started by:  John Kurtz


      1 Replies
      Reply #1 April 30, 2018 at 1:53 pm John, Somehow I missed this post–Sorry.. Anyway, I have repowered 2 Shamrock “Keel Drives” like yours and both turned out really well.. #1 was done using a Cummins 6BT 210 and a Velvet drive 1:1 gear ( like a ski-boat) , and the other one we used a Yanmar 6LPA 315–We called it the “Sham Rocket”.. Very fast and very smooth……………………………….Later…

      Last Post by:  Tony Athens posted: 3 months ago

    • Possible shamrock repower

      This topic has 1 reply, has 2 voices, and was last updated by john 4 months ago

      March 22, 2018 at 5:55 am Thinking of repowering a 1987 26′ shamrock stalker…..used mainly in freshwater lake but would like to trailer the boat to the coast for some fishing and diving adventures I was thinking about 380 ish hp. Boat weighs about 6000 pounds dry with the 350. Would like to gain speed, fuel efficiency, and dependability Currently has port and starboard fuel tanks 54 gal each Also have some concerns about prop clearance shaft size runnin…

      Started by:  John Kurtz


      1 Replies
      Reply #1 March 22, 2018 at 8:46 am I take it you want to put a diesel in it. I’m a big fan of shamrocks. They put a lot b series in the 26 shamrocks. Most were 210 hp. Big difference from that and 380 hp. Personally I think I would look for one of those. You have a ton of issues to deal with. Exhaust, fuel returns, shaft sizing, will it fit, prop clearance to name a few. This site has a lot of info on shamrocks https://forum.classicshamrock.net/ Great project though goo…

      Last Post by:  john posted: 4 months ago

    • Repowering 1990 luhrs 320

      This topic has 9 replies, has 3 voices, and was last updated by Tony Athens 5 months ago

      March 2, 2018 at 6:59 pm Hello everybody my name is Cesar Correia from Rhode Island i work on alot of diesels i work for an oil company full time servicing everything they have from diesel vans and gas jobs to large freight liners and kenworts. Lots of diagnosing also. That said i will be doing 90 percent of the work to try and keep my bank account in one piece..Originally the boat had twin 454 crusader 350hp models with 1 3/8 shaft. Originally with 454s 350hp model at …

      Started by:  Cesar


      9 Replies
      Reply #9 March 17, 2018 at 8:01 am Ceasar, You seem to have a great hands-on background in working on engines & equipment, but you are not understanding my responses. 1) The total operating WEIGHT of your finished vessel will be the main factor as to meeting your performance goals vs the HP you have to put into the props. Have you weighted your vessel and thought about what it will weigh after you are finished with the restoration/repower? Every extra pound you add will re…

      Last Post by:  Tony Athens posted: 5 months ago

    • Repower 35 Henriques Pilothouse

      This topic has 8 replies, has 3 voices, and was last updated by Tony Athens 5 months ago

      March 1, 2018 at 3:18 pm I have a 35 Maine Coaster pilothouse that I am considering downsizing the engine from a 420 to 370 Cummins Is this a reasonable possibility in theory. We use the boat for recreational fishing and don’t need a speed demon. Again this is a boat with a 4kw Onan genset, 300gallons of diesel max and 50 gallons of water if we were full. It is an 18000lb boat I need to repower but budget dictates and I’ve seen another similar boat a 34 Du…

      Started by:  finalee2005


      8 Replies
      Reply #8 March 6, 2018 at 7:01 pm From your answer to my post, I am not sure if you understood what points I was trying to make.. May I ask where you are located? Can you post some good pics of the 8.3 as currently installed in you vessel so we all can get an idea what what you are dealing with? Maybe a “smaller” engine will allow better service accessibility and that is part of the underlying issue or issues? But regardless, these engine are far from “ap…

      Last Post by:  Tony Athens posted: 5 months ago

    • Jersey Dawn Repower

      This topic has 6 replies, has 3 voices, and was last updated by RicM 6 months ago

      February 14, 2018 at 12:33 pm The boat in question is a 36 or 42 jersey dawn. Most 36s come with 3208 cats at 320hp and most 42s have 6-71s TIB 485s. From my research they are 18/19knt boats. My question is it is even possible to get these boats to that 27/28knt cruise with the newer technology? I am also aware that some of the older hulls don’t perform well at higher speeds so any information there would be appreciated as well. Ultimately, I don’t think I would …

      Started by:  Martin Padgett


      6 Replies
      Reply #6 February 16, 2018 at 3:53 pm Did something like this conversation occur over on BoatDiesel.com a while ago? In any case, if that’s the boat you want, and those are the engines you want, go for it. Life is too short to own an ugly boat, or is it Life is too ugly to own a short boat? Something like that, in any case, keep us informed about your quest. I for one would very much like to hear more about this project. Believe me, I spent many hours pondering the same questi…

      Last Post by:  RicM posted: 6 months ago

    • 3.9 stern drive repower?

      This topic has 2 replies, has 2 voices, and was last updated by Paul Harper 7 months ago

      December 28, 2017 at 11:51 am We inherited a 2958 Bayliner last year with twin 350’s & omc Cobra’s. After throwing some time into it, we have decided it needs repowered with engines & drives. The beam is 10.5 making the 350’s very difficult to work on. I work in heavy equipment repair & hate spark plugs. My neighbor at the marina has a 2001 sea sport with twin 3.9’s and Volvo drives, was wondering if this is a option? Thanks for any advic…

      Started by:  Paul Harper


      2 Replies
      Reply #2 December 29, 2017 at 6:08 pm Thanks Tony, we will probably fix what’s in it and use the boat for awhile till something pops up that has a good diesel package. Alot of nice boats out there with really outdated engines installed, hopefully that changes in the next few years. Paul. 1989 Bayliner 2958 Avanti.

      Last Post by:  Paul Harper posted: 7 months ago

    • Repowering a Baja

      This topic has 1 reply, has 2 voices, and was last updated by Tony Athens 9 months ago

      October 12, 2017 at 6:34 am Let me preface this by saying I have not purchased any boat to do this in yet, this is just a really wild idea in my mind that I really want to make happen, and would like some input as to what your thoughts or concerns would be. I am looking at getting a 26-30 foot Baja Sport powerboat if you will, going to get one with a 454 BBC or bigger in it with a Bravo drive to it at minimum. Now I have always been a diesel guy and would love to do a dro…

      Started by:  Bryan Pence


      1 Replies
      Reply #1 November 16, 2017 at 9:59 pm I guess this is another one that got missed.. Sorry.. Before I get into the “has anyone done this” , (I have) let me ask you this……………..Do you have a general “budget” for such a project and do you have a general sketch or some pictures of what you have now vs, what you want to end up with.. That would make it a lot easier to comment effectively.. Tony Tony Athens Seaboard Founder Go here fo…

      Last Post by:  Tony Athens posted: 9 months ago

    • CAT 3126 420 to Cummins 6CTA 430

      This topic has 6 replies, has 3 voices, and was last updated by Tony Athens 9 months ago

      October 25, 2017 at 8:26 am Posting this for a guy on down east boat forum. I’ve asked him to join……”hell it’s free” !!!!! “hey bill I know your a cummins guy and are very knowledgeable in this are I’m thinking for down the road I have a cat 3126B 420hp now with a td2.5:1 gear if I put in a recon 6cta 430hp could I use the same gear the cat turns 2800 wot the cummins 2600 wot” The boat is a beautiful 36 H&H down east lo…

      Started by:  Bill Desmarais


      6 Replies
      Reply #6 October 29, 2017 at 12:49 pm Propped right, the 6CTA 8.3 will turn at least 2750 and can run all day at 2400 RPM.. If you are working the motor super easy, just add 1-2″ of pitch to get the R’s down to 2200 or so to get your happy vessel speed. Don’t confuse MINIMUM rated RPM or test cell data with how this engine really likes to be propped in the field under real ocean/working conditions. . Tony Tony Athens Seaboard Founder Go here for the latest stuf…

      Last Post by:  Tony Athens posted: 9 months ago

    • Jersey Sportfish Repower

      This topic has 8 replies, has 5 voices, and was last updated by leonaj99 9 months ago

      October 9, 2017 at 6:38 pm The boat is a 42′ 1993 Jersey Dawn III sport fish. The engines are 6-71 TIB’s, 485HP, that have about 1000 hours on them since full rebuilds. They run fine, but they are noisy, dirty, and smelly. It’s a great boat, and my wife and I both love the interior layout and it’s livability. We are now retired and are contemplating the options of running this boat back and forth from RI to FL vs staging it down there and buying …

      Started by:  RicM


      8 Replies
      Reply #8 October 22, 2017 at 8:16 am Rick good luck in your repower and in making the tough decisions. I just want to emphasize Tony’s comments regarding sub system upgrades/improvements. Having done a single engine repower myself in the past and having done most of it myself I found an awful lot to do as soon as the old engine was out. Old thru hulls? Now I have good access so time to install new ones. Old water system plumbing? Gone and a new system installed with proper a…

      Last Post by:  leonaj99 posted: 9 months ago

    • Repower Options ?

      This topic has 6 replies, has 3 voices, and was last updated by Bill Desmarais 11 months ago

      September 1, 2017 at 7:09 am I’m posting this question for a boat owner friend who has a 32 H&H (Osmond Beal down east) lobster boat. Right now the boat is powered by a 1999 Isuzu 6 cyl. Model A-6BG1T 230 hp rated @ 2500 rpms. The engine is keel cooled with dry stack exhaust. Tranny is a ZF63A 2:1 gear, 1.5” shaft with 24X22 #3 cup prop. Weight is a guess @ 12,000 lbs +-. Owner stated the boat is “heavy” for the sea trial. I sea trialed the boat this past week …

      Started by:  Bill Desmarais


      6 Replies
      Reply #6 September 3, 2017 at 8:07 am Rob, I’m confident the repower of this older 32 H&H will be no more than a ReCon engine. 25 Terry Jason down east, 370 6BTA 28 Henriques Sport Fish, twin Volvo 200 41 PA s

      Last Post by:  Bill Desmarais posted: 11 months ago

    • QSC propping to engine load

      This topic has 2 replies, has 2 voices, and was last updated by Luke Nelson 1 year ago

      June 14, 2017 at 6:03 pm Hi Guys, I am after some input on engine load to propping. I have just swapped out a pair of 3208’s to qsc 540’s. I think I may be close but everyone wants more speed if they can have it. The props were calculated on the 490 hp curve to keep within the shaft limits for survey( I am using marinex hs22 2.25). I can post the full numbers but at 2400rpm I get 19.5 knots @ 120 LPH and 52% load. At 2600 I get 22 knots and 74%. The engine …

      Started by:  Luke Nelson


      2 Replies
      Reply #2 June 25, 2017 at 2:56 am Thanks Tony, It makes sense when you say it like that. The sea water sides are on my list to strip and clean. thanks Luke Attachments:You must be logged in to access attached files.

      Last Post by:  Luke Nelson posted: 1 year ago

    • Repower 34' Libby with Cummins QSB 5.9 480

      This topic has 2 replies, has 2 voices, and was last updated by John Albaum 1 year ago

      June 14, 2017 at 9:14 am I’m looking to repower my 34′ lobster boat(Libby 34×13). I have a Deere 6068SFM50 rated at 265hp with a ZF280 at 2:1 to a 2″ shaft spinning a 24×25 wheel at the moment. The engine I’m looking at is a very low hour QSB 5.9 at 480hp. I know the engine will fit and my gear and shaft will handle the horsepower. My questions revolve around the exhaust and the power steering pump that is already on the engine. Th…

      Started by:  John Albaum


      2 Replies
      Reply #2 June 14, 2017 at 10:08 pm Thanks for the reply. With the Deere I can make a little over 19kts at WOT and about 13.5gph, and that’s right were I would like to cruise, so I feel like that wouldn’t be too hard for the 480 to do. I’ve read they can cruise comfortably at 17ish gph. I’d be doing 300-400 hrs per year so not too much. I’ve attached a picture of the engine with the power steering pump attached. I don’t know if this is a Cu…

      Last Post by:  John Albaum posted: 1 year ago

    • Prop Sizing Question

      This topic has 1 reply, has 2 voices, and was last updated by Tony Athens 1 year ago

      May 31, 2017 at 8:56 am Prop sizing. question. These are 6BTA- 300 in a 34′ Hatteras Convertible. 12.5 beam – 26000 lbs loaded (No Trim tabs) ZF220A 1:5-1 gears. 3100 rpm NO LOAD – Current props: 4Blade Nibral – 20 X 19.5 X 1.5 WOT= 2675 RPM – NO BLACK SMOKE UNTIL IT GETS JUST OVER THE 2600 MARK, 2675 WAS ALL SHE HAD TO GIVE. Looking to get 2950rpm. NOTE**Started with props 20 X 21 X1.5 that gave me a WOT of 2600 RPM. The 20 X21 set up…

      Started by:  paul j


      1 Replies
      Reply #1 June 2, 2017 at 7:24 am Paul, These are early 300B’s and they like to spin up easy to well OVER 2900 RPM when your vessel is loaded up as you use it–Typically I say “loaded for bear”…. Basically, you cannot under prop this engine as long as you are happy with the vessel speed at cruise RPM’s in the 2300-2500 RPM range.. Tell your prop guy this—————-Reduce my pitch/diameter/Cup or ??, until the engine …

      Last Post by:  Tony Athens posted: 1 year ago

    • Cutlass bearing

      This topic has 1 reply, has 2 voices, and was last updated by Tony Athens 1 year ago

      April 30, 2017 at 4:11 pm just hat my shaft shortened because when I repowered I had to slide the engine back I needed to replace cutlass so everything was out good time to do it now it’s all back together my question is new cutlass bearing should I be able to lift on the shaft and get any movement 

      Started by:  Derek chandler


      1 Replies
      Reply #1 May 9, 2017 at 8:00 pm All cutless type bearings are “sloppy” as to a shaft fit ,  Maybe a  new 1.5″ cutless is .010-015″ over… If the Bearing is in perfect alignment with the shaft going thru it, yes you can always feel some lift.. As that alignment gets skewed, than is gets less and less.. Another issue is the ID of the strut as to concentricity–Many struts have out of round bores and will crush the bearing as it’s pressed…

      Last Post by:  Tony Athens posted: 1 year ago

    • QSC 540 or C9 565

      This topic has 8 replies, has 3 voices, and was last updated by Bryan 1 year ago

      December 2, 2016 at 4:29 pm So what would be peoples thoughts?  The QSC’s have 4000 hours and the C9’s have 2000 hours. It would be  prop application for around 700 hours a year, both would be propped down to 500hp  and driven for the best part at around 1800  rpm. Discounting the general condition  of the engines would one be seen as the better choice? I had a water ingress incident and have 2 wet 3208’s and it seems the right time to upgrade. I und…

      Started by:  Luke Nelson


      8 Replies
      Reply #8 January 12, 2017 at 5:22 pm <p>Well the early pumps had issues that was recognized by caterpillar in a service letter. I’ve seen heui pumps last for upwards of 6000 hours and others 1500 hours was all the time they lasted this is where strict oil changes and regular maintenance ( anodes etc.) come into play, most times the pump can not make full pressure and the engine runs poorly at higher rpm. The downfall is when the pump fails and contaminates the oil rail …

      Last Post by:  Bryan posted: 1 year ago

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