Cummins Marine Diesel Repower Specialists › Forums › Boats & Repowers › 1997 Bertram 36 Repower

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  • December 27, 2017 at 3:03 pm #26599

    Tim Flynn
    Participant
    Country: United States

    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/fumes and quiet motors important to us. So considering a repower to Cummins QSM, QSC or QSB. Goal is to achieve close to 20-22 GPH at 20 knots if possible. Budget is roughly $100k…would love to do for less, but willing to spend more to get it right. I assume the current 450 Diamonds can be sold to offset the repower cost.

    Is this a crazy idea? I am not an expert in this stuff so please excuse any ignorance in this post!!

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  • May 2, 2018 at 8:12 am #31802

    Tim Schantz
    Participant
    Vessel Name: Miss Quinn
    Engines: QSB6.7 550hp
    Location: Cape May NJ
    Country: USA

    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’s at 2300 RPM’s I would cruise in the 24 knot range burning around 34 gallons an hour. In my opinion this hull seems to come alive in excess of 23 or 24 knots. Becoming much more efficient and needing a lot less tab to run correctly. With the knew motors in excess of 25 knots I am running with the tabs fully retracted.

    As far as the repower goes, you are not going to touch it for less than $100k. Just the parts along are going to cost you in that range, Engines, Gears and Glendinning control system. Now factor in all of the labor and miscellaneous parts. If you are able to sell the existing engines and gears for a good price you may be able to hit the $100K mark. Good news is the boat performs awesome with the new motors. We are hitting 36 knots at WOT.

    January 3, 2018 at 7:27 pm #26757

    Tony Athens
    Moderator
    Vessel Name: Local Banks
    Engines: QSB 6.7 550 HP
    Location: Oxnard, CA
    Country: USA

    Nick (?),

    Your reply is perfect for an comparison, but like I learned very well over the last 30 years ago, that there are no two boats are the same, and most times, not even close when you start talking max RPM’s , vessel speed at cruise RPM’s, etc etc……..

    But regardless, your input for perspective purposes is extremely helpful..

    At this point our poster, Tim, needs to come to grips that the 6CTA 8.3 450 Diamonds are right for this vessel as long as they are propped correctly and have been kept up within reason since new.. . At this point, that is still in question..

    He needs to reach out a tad more, and then actually LISTEN, and not speculate.

    Tony

    January 3, 2018 at 2:26 pm #26751

    Nicholas
    Participant
    Engines: 1200hp Man d28 v12
    Location: Cocoa Beach, Fl
    Country: USA

    I apologize if this is a duplicate; I thought I posted a reply but after waiting several minutes it never seemed to show up…

    I have a 1985 Betram 38 convertible with cummins 480CE’s. Basically a slightly bigger version of your hull with very similar engines. I have an aluminum T-top and outriggers, and typical “junk” onboard. I get about 20kts at 1900 RPM, 23 at 2000, 25 at 2200, 27 at 2350, and about 30 at WOT (not that I run there, but it did make 30 kts + on the original sea trial). Those numbers are about average; I can do slightly better with flat conditions and a tail wind or slightly worse in a choppy head sea. Generally I figure about 1 statute mpg at cruise and I can get close to 1 nmpg in ideal conditions. I’d think 22 gph at 20 kts would be pretty attainable in that Bertram 36 with the existing engines if they are running properly.

    December 29, 2017 at 4:31 pm #26650

    Bill Desmarais
    Moderator
    Vessel Name: Extremist
    Engines: Cummins 6BTA 370
    Location: Portsmouth, NH
    Country: United States

    This forum……it’s how we all learn !

    December 28, 2017 at 4:34 pm #26625

    Tim Flynn
    Participant
    Country: United States
    Bill Desmarais wrote:

    Tim,

    Bill D here.
    Guy at my marina runs a 36 Luhrs Tournament with the same engines.
    He never complains about performance.
    Maybe not apples to apples with the Bertram but close.

    IMO the ownerā€™s numbers are off.

    Iā€™m sure you noticed already, but if not, Tony Athens who owns Seaboard Marine with his family is ā€œjust up the street from youā€ in Oxnard.

    Keep us posted,

    Bill D

    Thanks for the insight Bill. Luhrs 36 is a bit lighter than the Bertram, but agreed, it is a good comparison. And I also agree that the owners numbers are likely off.

    I would hope to involve Tony as much as possible in the process of inspecting this boat. Thanks so much for your help!

    December 28, 2017 at 4:30 pm #26624

    Bill Desmarais
    Moderator
    Vessel Name: Extremist
    Engines: Cummins 6BTA 370
    Location: Portsmouth, NH
    Country: United States

    Tim,

    Bill D here.
    Guy at my marina runs a 36 Luhrs Tournament with the same engines.
    He never complains about performance.
    Maybe not apples to apples with the Bertram but close.

    IMO the owner’s numbers are off.

    I’m sure you noticed already, but if not, Tony Athens who owns Seaboard Marine with his family is “just up the street from you” in Oxnard.

    Keep us posted,

    Bill D

    December 28, 2017 at 9:10 am #26614

    Tim Flynn
    Participant
    Country: United States
    Rob Schepis wrote:

    You will need to bring a handheld photo(laser) tach along. The data is only useful if it is accurate. Laser tachs are cheap and easy and something that adds great value to any boat owners tool bag. Especially if youā€™re in the marketā€¦

    The CTAā€™s will do you just fine if setup right and you will have an enormous amount of ā€œfree fuelā€ to burn with the money you do not spend on a repower. If the current engines are healthy, IMO a repower makes zero sense and ā€œzero centsā€ā€¦

    Good stuff. I will buy a Laser tach for the sea trial. Any particular brand you recommend?

    With respect to the repower, I understand (and do agree) that on the face of it, a repower makes no sense (or cents). But this boat will be in charter and will need a repower in next 5 years anyway. So we are going to put the money in at some point.

    Given that, it may make sense to do the repower sooner (next winter) so we can get more benefit from the better engines. That is why understanding the potential cost of a repower is so important. Pretty sure we do a Cummins repower if and when it made sense.

    Thanks for your response! Very helpful

    December 28, 2017 at 9:04 am #26613

    Tim Flynn
    Participant
    Country: United States

    Thanks Glenn. Very good and helpful perspective. This boat is actually going to be used in fishing charter (4pack/6 pack) out of San Diego so fuel efficiency is critical to the business model. During peak times, we will be running the boat 30+ hours per week. In order to provide great customer service (reasonable speed to the fishing grounds) and competitive pricing, fuel efficiency really matters.

    I do think it is possible to make this work with the 450C’s, but I still would like to explore the cost of a repower. We are going to have repower at some point in next 5 years anyway….

    Thanks again for your response and feedback

    December 28, 2017 at 6:56 am #26609

    glenn111
    Participant

    Usually the first thing a new/typical buyer (RECREATIONAL boater) thinks about when considering to purchase a boat is the fuel economy of the vessel. How may gallons per hour at cruise. Experience shows that after several years of average usage of 150 – 200 hrs/yr, and a lot less if you’re boating in a Northern State, the fuel cost is the least significant item on the boaters expense list….especially if the boat is “getting up” in age. Rob’s comments are on-target from what I’ve seen and experienced. Sounds like it could be a very sound boat with great engines normally.

    December 28, 2017 at 6:43 am #26608

    Rob Schepis
    Forum Moderator
    Vessel Name: Tenacious
    Engines: 6BTA 5.9 330's - "Seaboard Style"
    Location: Long Island, NY
    Country: USA

    You will need to bring a handheld photo(laser) tach along. The data is only useful if it is accurate. Laser tachs are cheap and easy and something that adds great value to any boat owners tool bag. Especially if youā€™re in the market…

    The CTAā€™s will do you just fine if setup right and you will have an enormous amount of ā€œfree fuelā€ to burn with the money you do not spend on a repower. If the current engines are healthy, IMO a repower makes zero sense and ā€œzero centsā€…

    December 27, 2017 at 5:10 pm #26602

    Corey Schmidt
    Forum Moderator
    Vessel Name: Rebel Belle
    Engines: Cummins
    Location: Oxnard, CA
    Country: USA

    Sea trial day

    Bring a good camera to take lots of good clear pictures of the engines installed in the boat and a notepad to record as much info as possible… this will tell us the info we need to be able to answer questions re: efficiency, etc.

    December 27, 2017 at 4:06 pm #26601

    Tim Flynn
    Participant
    Country: United States

    Thanks Chris. We have not had a sea trial yet, so all my info is coming from the owner. We will need to sea trial to verify the RPMs at WOT and the RPMs required for 20 knots.

    Let me know if you have thoughts on the cost and sensibility of a repower to get better efficiency, and less smoke/noise. Seems like the 450C’s should be fine, but owners info giving me some pause.

    Thanks again

    December 27, 2017 at 3:58 pm #26600

    Corey Schmidt
    Forum Moderator
    Vessel Name: Rebel Belle
    Engines: Cummins
    Location: Oxnard, CA
    Country: USA

    Tim, I’ll let Tony chime in on this one but it seems to me that the 430/450 engines are plenty of power for a boat of that size. And you’re right, according to the power curve those engines should burn no more than ~10.5 GPH at 1900 RPM so not sure how he’s coming up with the fuel burn numbers but it appears the engines are burning too much fuel (over-loaded) if he is in fact accurate.

    Can both engines reach OVER 2700++ RPM when at wide open throttle (WOT) and reach it easily?

    At what RPM does the boat go 20 knots now?

    These engines like to see RPM, they do not like to be lugged down…

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