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B60 performance with 3412’s

Discussion in 'Bertram Yacht' started by CWV, Aug 1, 2021.

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  1. Capt J

    Capt J Senior Member

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    The problem is NOT in the props. The problem is in the engines. You're turning rated RPM, so why on earth are you only seeing 94/96% load. You should be seeing 100% load. Sounds like you have a starvation issue. Either fuel or Air......but definately an issue there, not in the props. The governor should be at 2400 rpms (if memory serves me right) on 3412's, so you should see 100% load, not 94/96%, something is creating an issue where the engine can't get enough air or fuel to make 100% load........perhaps something as simple as fuel vent, or bad air filters (yes you can only clean washable air filters so many times where they start to crush at full bore and restrict flow, but usually see black smoke when this happens. )
  2. CWV

    CWV Member

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    Interesting insight. Had a similar challenge post-repower on our B50 with new cats (replaced 8v92) because we were under propped badly - likely due to taking a lot of weight out of the boat. Took 2100 rpm to hit 80% load and amazingly couldn’t hit 100% load even dragging one motor at idle (test performed by Cat’s TC at Greg Poole). We were running 60% range load factors at nearly -1900 rpm cruise if I recall correctly, and while loaded for bear. New Veem interceptors ultimately fixed this and we picked up 2-3 knots and had the load dialed in perfectly. I’m kind of leaning more prop tuning and bottom job, but will pass your valued feedback to the mechanic for his thoughts. Boat ran great, just a lack of speed issue. No smoke.

    Should anything more come to mind, please keep the ideas coming ! :)
  3. Pascal

    Pascal Senior Member

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    A vacuum building in the ER? Was the ER door open ? Don’t forget the captain works for the owner / seller ...
    CWV likes this.
  4. Capt J

    Capt J Senior Member

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    Need all of the information from the computers on seatrial to see what's going on: IE fuel pressure, boost pressure, air pressure at air filter, EGT's, could also be not enough airflow from the engine room vents as Pascal is mentioning. I'm thinking air, turbo's, dirty aftercoolers, or bad air filters, as 100% load generally is measured as fuel rack at full tilt.
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  5. CWV

    CWV Member

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    Door was in fact open, yes.
  6. mapism

    mapism Senior Member

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    I'm struggling a bit with your reasoning.
    I mean, I can't rule out some engine problem obviously, but in principle if the engines reach the rated RPM with a light(ish) load, the first logical assumption is that they have some room left for pushing a bit longer props.

    If anything, it's the extent of the difference that doesn't stack up.
    In fact, it would take a significant pitch increase to gain 5 kts at the same RPM, and I very much doubt that the residual engines power theoretically still available from 94/96% to 100% could cope with it.
  7. Capt J

    Capt J Senior Member

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    The engines are rated for 2300 rpms WOT, but will turn 2400 rpms before the computer stops them from making more rpms. They're hitting 2310/2320 rpms, but load is only 94/96%, they should be seeing 100% load at WOT where the engines cannot make more HP/RPM's, but they're not. Something is stopping the engines from making full HP and therefore probably another 50 rpms. See post #2.

    But the engine computers aren't seeing enough air or boost, to give the injectors full rack to make 100% load and that final bit of HP.
  8. mapism

    mapism Senior Member

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    As I recall, high idle in that engine is set at the max rated RPM +20, not +100.
    I can't swear to be correct, but I am sure you can now see the logic of my previous reasoning, which was based on this assumption.
    OTOH, if your +100 assumption is correct, I agree that there's something else than the prop restricting the engine to run faster and reach full load.
  9. CWV

    CWV Member

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    Really good perspective, thanks guys.

    Just as an aside, props weren’t stamped properly for us to confirm size during survey. Seller advised this morning they may have another set, in boxes; if so, we’ll compare the boxed props against other known sistership vessel data with respect to size / performance.

    Thinking otherwise, and purely hypothetical, a bottom job might yield a knot and maybe we can find 2 knots within midrange rpm if we get the load numbers up through tuning. I’m not a run it on the pins guy, but I don’t mind running 75-80% load so long as below ~2000 rpm. Fingers crossed.

    I’m surprised that there’s so little data readily available on these vessels, despite being around for 20 years. Broker is going to check vessel books for any factory data; he also shared that capt’n comment about speed was when boat was new and being picked up from factory (insert eye roll).
  10. RER

    RER Senior Member

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    Not much data because it’s a limited production boat, and as you stated it’s 20 years old.
    Other than a very generalized baseline I don’t see what the data from another boat is going to do for you. There are just too many variables to put two 60’ Bertram’s side by side and expect them to perform within one knot of each other. Especially if you are using data from when that model was brand new.
    It sounds like you are coming from a repowered boat with a latest/greatest peak performance perspective. I think you need to factor in some old boat syndrome on the 60.
    Last edited: Aug 2, 2021
  11. d_meister

    d_meister Senior Member

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    I was involved with a brand new sportfisher that wouldn't come up to rated speed/RPM. The props came off and were reworked multiple times. Ultimately, the solution was to replace the 2-micron Racors with 30's and switch the Racor selector valves to "Both". It's good to start with the simple and cheap variables, first.
    Don't ignore the fuel question. Diesel is compounded at the refinery differently for different seasons, especially for algal growth prevention during winter months. Lab testing will answer the cetane rating issue. The object is to eliminate variables, and you won't know if too many factors are "x".
  12. Pascal

    Pascal Senior Member

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    Racors should indeed use 30 microns but they can run on a single racor, don’t have to run on both.

    I ve always run the 3412s and C32s, and now the 16V2000s on one racor at a time.

    Any fuel supply issue should result in low pressure. The surveyor should also be able to tell if fuel flow was correct on the pins.
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  13. Capt Ralph

    Capt Ralph Senior Member

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    Mud filters should be 30mic and secondarys around 10 to 16mic.
  14. CWV

    CWV Member

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    I hear ya, but old(slow)-boat syndrome is 100% not what I'm looking for; I expect a fair amount of mechanical reconditioning with respect to systems and customizing to my standards, all of which can be easily factored into the price and anticipated depreciation.

    When the capt'n gives you performance number which is spot on with all other B60's of similar vintage and power, then the boat misses the mark by about 5 knots... And when vessel is (hypothetically) lighter than the others - sans tower / davit, fish gear, etc... It makes you wonder, particularly when it does not hit 100% load at WOT and load factors are very low at traditional cruise RPM's (yep - - I understand this can be a good thing for longevity)... I'm looking for performance that matches other B60's - - or within reason. The disparity is just too great at this point.

    Would be happy with 28-30kn cruise between 1800-2000 and a 35kn WOT, which is about 2 knots off spec and other boats.

    Our Repowered and Refit B50 is actually a 1988 hull. We've owned her for 10 years this month and yes, all systems are all 'like new' thanks to about 3.5 years in the yard during our ownership. I get it and I'm not doing that again. Also not keen on going back to 20-25kn cruise speeds with performance of thirsty Detroit 8v92's; I'd double the budget on this B60 and go Carolina boat or 2005-ish Viking 61 first (each of which probably also needs work, of course). Speaking of which, custom boats probably carry considerably more variability between hulls than any production boat, no?

    BTW, for those following along..Was just told the travel lift weight gauge hasn't been working for quite some time, as per surveyor who has done several boats at that location. Still awaiting formal mechanic's report info / response to follow up questions.

    Thank you all again for your feedback. Some really good points being made, providing some further thought and consideration on my part with regard to different elements of this boat. It'll prompt a great convo or two with the professionals we've hired to help inspect her.

    Gratefully yours,
    -v
  15. RER

    RER Senior Member

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    I’ve been a party to more surveys than I can remember. Many hundreds. Many boatyards. Boats 30’ to 130’ and I can’t recall ever seeing a travel lift weight (when the scale happened to be working) that I or anyone in the survey party would count on as accurate.
    And just FYI sometimes the full time captain can be more hindrance than help on a sale. Sometimes a sale means they’re out of a job. I know the full time captains here might have something to say about that but I know what I know.
  16. Capt J

    Capt J Senior Member

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    I run 10 micron Racors- 30 micron racors are too large for today's lower sulpher diesel. I've come across 5 different yachts, mostly a few years old or less where the racors looked clean and weren't clogged and the secondaries so clogged the motors wouldn't make fuel pressure. Anything over 1500 hp, should have 2 racors open IMO.

    That being said. I'd take a 61' viking seven ways till Sunday over a 60' Bertram, and for a number of reasons.
    LM Viking likes this.
  17. Capt Ralph

    Capt Ralph Senior Member

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    Wait, Is this a F E B?
  18. Pascal

    Pascal Senior Member

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    the question is how many hours were on the secondaries. Often some owners replace the racors but not the secondaries. I replace both at every oil change and never had an issue using 30 microns. We do about 400 to 500 hours a year

    every mechanic I ve had working on the boat, Cat and now MTU, said they can run on one racor. 1400hp 3412, 1650 C32 and 2000hp 16V2000. I just like having a clean racor ready to go should I get a load of bad fuel.
  19. CWV

    CWV Member

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    Secondaries - just changed. Maybe 2 hours at most.

    More facts... We still don't know the prop measurements or confirmed vessel weight, but seller has a set of spare wheels in storage that reportedly came off the boat but not yet reconditioned. Stamped as 32x50 Rolla's. Calls to prop gurus won't bear fruit unless we first know what we're working with and have specific data points. However, one speculated that older wheels which have likely been reconditioned at some point over the last 10, 15 or 20 years can often end up losing some diameter in the process. Some prop shops tend to increase pitch while reconditioning to achieve the appropriate RPM at WOT - - this could potentially lead to the type of performance loss we're seeing. (another fact: I'm beyond my competency here)

    I guess with so much invested at this point, rather than walk, we need to now ask the seller to get us wheel measurements and help us identify the missing performance or be faced with accepting a 60' pig of a boat which has a relatively small resale market when economy or fuel prices turn for the worse. IMO, there's enough other small stuff on the vessel w/ 20 years of age and deferred maintenance, I would have to wish them good luck selling her for the top-dollar being sought.

    The survey reports have facts that show she needs some considerable TLC beyond routine maintenance; none of which are specifically impacting performance and nor are they deal breakers for me. It's just time, project management and a few buckets of money. I don't think negotiating the survey findings makes sense until we have the performance matter sorted.

    Again, I remain grateful for your wealth of knowledge and perspective. THANK YOU to all whom have chimed in.
  20. Capt J

    Capt J Senior Member

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    What ratio are the gears?