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Cat 3208 Question

Discussion in 'Engines' started by NorCalBoater, Feb 4, 2012.

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  1. NorCalBoater

    NorCalBoater New Member

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    I am in the final process of buying a 1984 50' Kha Shing CPMY. during the sea trial the boat at WOT got to 2650 RPMs as stated on digital tachs.

    My understanding is that the Cats should be at 2800 at WOT. Assuming the tachs are correct do I have a prop issue? The bottom is clean and the fuel load was light. The surveyor said that the engines could be governed.

    This is my first diesel boat and I want to get all the bases covered.

    Thanks,
    Shawn
  2. Capt Ralph

    Capt Ralph Senior Member

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    Get a mechanical surveyor on board. He should be able to answer real quick if your tacs are correct and if it's the governor holding the rpms back.

    You need 200 more rpm.
  3. dsharp

    dsharp Senior Member

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    See what it turns up in neutral. That will tell you if it's governed. I'm not familiar with the boat but if it's a planing hull you need to run it in deep water with a full load of fuel to see where you are with the props. If the tachs are accurate it sounds like you need to take an inch of pitch out to pick up approx. 200 rpm. What size props were on the boat when it was new?
  4. dennismc

    dennismc Senior Member

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    Some owners (like me) take 2-250 rpm of the top in order to preserve wear on the mains and prefer to run at that top rpm, however if the boat is not performing and needs the extra rpm, then yes, fix it.worth checking first before changing props etc.
  5. RT46

    RT46 Senior Member

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    get a mechanical survey, it will be money well spent.

    you will want the boat to reach max RMP at WOT under load....
    a no load test will confirm that your gov's are properly set.

    if not getting max rmp at wot under load you can substantially shorten the life of a diesel.

    You may have just have to take some pitch out of the props. It could be that simple. A clean bottom and fresh scanned props will help you get an accurate

    An engine survey by a qualified CAT tech shouldnt cost more than a few hundred dollars for a pair of 3208s.

    Also, oil analysis can be a helpful look into the life and condition of an engine, but sometimes hours on oil is not accurate. Oil analysis is best if you have a documented history of the samples and hours on oil along with fuel through the engines.
  6. RER

    RER Senior Member

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    The full spa treatment from a CAT certified tech for a pair of 3208's including sea trial and oil analysis, you're looking at more like $800 - $1,000 or more.

    Still, money well spent though.
  7. RT46

    RT46 Senior Member

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    RER,

    i agree you are correct in your cost estimate.

    worth every penny....

    RT46


    I also recommend that the buyer be present for the hull and system survey.

    I like to observe and ask questions along the way.
    Some surveyors might not like this, but if i am paying them, I want to be there to gain knowledge and awareness and ask questions....

    Plus the spoken word is often more descriptive than a written report.
  8. RER

    RER Senior Member

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    ...and the seller says "Well I don't know what to tell you, I never run the boat that hard" ...it's a common problem with older boats. Original prop specs are calculated for a bare boat with fresh motors. Manufacturers want to demonstrate peak performance. Those calculations change over time with added weight and as motors get older. You need to determine if the boat is propped correctly. Don't guess. And you need a mechanic shooting the rpms in the engine room. Don't buy a boat without a mechanical inspection from a qualified tech - in addition to the vessel survey.
  9. RT46

    RT46 Senior Member

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    RER,

    you on right on point.

    RT46
  10. captjohn22

    captjohn22 Member

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    Be careful

    I have 3208 TA's 375 HP in a 38' Ocean Yacht. In neutral they should spin up to 3000 RPM. FULLY loaded [fuel water gear and people ] you should go a little over 2800 RPM with a clean bottom and no opposing wind or current. If necessary do an average of a two way run.
  11. NorCalBoater

    NorCalBoater New Member

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    Thanks for all of the quick replies.

    More info:
    The engines have 2000 hours. A mechanical survey was done with nothing mentioned about RPMs but the boat was not taken out during the mechanical. The oil analysis came back showing glycol in the port engine. During the sea trial and on the way to haul out for hull survey. The surveyor found a blown head gasket on the port engine. I have used this surveyor 3 times and trust him.

    The current props are 20 x 26 and I have no way of knowing if they are original. The boat is 28 years old and had a couple of POs. The surveyor and I were both surprised by the small diameter but a larger prop with the same pitch would only bring the RPMs down more at WOT.

    I am going to have the seller's broker run the SB engine WOT in neutral but we don't want to do the port until the repairs are made. The seller is willing to make the repairs so I will most likely move forward with this boat. The positives far outweigh the negatives.

    Thanks again for all of your wisdom and insight.

    Shawn
  12. dennismc

    dennismc Senior Member

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    When you say Glycol inn the port engine you mean "real " glycol ? wow....there goes a set of bearings.....
  13. Capt J

    Capt J Senior Member

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    Depending on how much glycol, a little bit won't wash the bearings. Or a lot of glycol for a very brief period of time, and I mean very brief.

    I manage a sistership to the one you're looking to buy. It's a well built boat and roomy for it's size. The engines in the boat I manage were only supposed to go 2600 rpm's top end, not 2800 rpms. Check the serial numbers against what CAT recommends, but it's not uncommon to have to remove a little bit of pitch on a boat of that age. Also, depending, I've peeled all of the layers of bottom paint on a boat of that age and gained 100rpms. There's a lot of weight in all of the layers of bottom paint that build up as well as the surface isn't as true.
  14. captjohn22

    captjohn22 Member

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    A little more info

    My transmissions have a 1.5 to 1 gear ratio. I have been running 22x21x4 blades with a light cup, that now after 10 years only make 2700 RPM.
    The diamater is in part a factor of the tip clearence to the hull. You may also have a higher gear ratio than I.
    I also have a set of 22x24x3 blades that were the original spec from Ocean Yacht but now they only spin to 2650 RPM. Both sets are in the shop at this time.
    Call your local Cat dealer with the engine S/N's like the previous poster suggested to make sure what they should spin up to.
    Over propping will shorten the life of your engines and does not save on fuel like some people think. It raises the combustion temps which is detremental to engine life.
  15. NorCalBoater

    NorCalBoater New Member

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    Trace amounts of glycol. I will get the serial numbers and call CAT. There are several layers of bottom paint but we are moving it from salt water to fresh and we are planning to remove the old paint and have fresh water paint applied.

    Thanks for the additional info Capt. This is a roomy boat and feels very solid. Our sea trial in San Francisco Bay was with 20kt winds and about a 2' wind chop. Nothing rattled, nothing came loose, nothing broke. It also has $30k worth of new networked electronics and completely rewired panels (part of the $30k).And stabilizers. :)
    Just got a call from the broker and the SB engine hits 2850 at WOT in neutral....again, assuming the tachs are correct.

    This will all get sorted out. Thanks everyone.

    Shawn
  16. RT46

    RT46 Senior Member

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    depending on how long the head gasket has been leaking...the bearings may be still ok.....any other metals high in the oil?

    If the owner makes repairs on the head gasket, then I would want full receipts and documents from a qualified CAT guy. ask for tranferrable warranty.

    Sometimes you are better getting allowances and having the repairs done yourself.

    also, you really need to know exactly which 3208 you have in there, i suspect WOT will be different for the N/As vs the Ts, vs the TAs and whatever other variation was available for the 3208s
  17. NorCalBoater

    NorCalBoater New Member

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    Thanks RT.

    These are the 375 hp TAs. The CAT site shows WOT as 2800 RPM. We are planning to ask for an allowance after we get quotes for repair and then have the repairs done. We will get the quotes from an authorized CAT service tech.

    Again, I want to thank all of you for responding. This is not my first large boat but it will be my first oil burner and all of your generous knowledge helps me with this process.

    Shawn
  18. Capt Ralph

    Capt Ralph Senior Member

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    Fresh Water

    You brought up a point a few back and nobody picked up on it. Your moving the boat to fresh water?
    Is that way up river or on a lake your going to do most of it's use on? I know nothing about your part of the world on how fresh the fresh water is.

    In fresh water (lower density water), your boat will sit lower, have more drag and run slower. This ads more issues to your rpm questions.
    Look well at your boot stripe now, you may need to raise it an inch or two during your next bottom job.

    On the blown head gasket main;
    With out all of the hot exhaust gasses it needs, the turbo, then whole engine, Can not make full horsepower or rpm. If it can not make full hp, the second main engine is now under a larger load and may not be able to make up the missing horsepower and make it's rpm (domino effect).
    Get that engine fixed and oil changed, and run-em-again. Make sure engine syncs are off.

    More thoughts;
    Is there a lot of extra gear on board since factory? BBQ grills, extra anchor, all chain, tower, all curtains, Tools and spares? Bow comes up or a monster of a bow wave?
  19. captjohn22

    captjohn22 Member

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    You make a good point.

    I would recomend you do not change the props until the engine repair is compleated and the boat sea trialed again to see what they spin up to.
  20. Capt J

    Capt J Senior Member

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    I second this as well.