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54' Offshore won't get on plane

Discussion in 'Technical Discussion' started by CSkipR, Sep 26, 2020.

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  1. CSkipR

    CSkipR Member

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    A friend has owned this boat for approx 3-4 yrs. The boat has C18 Cats 700hp ea and about two months ago it would not get up on plane. Its a relatively slow boat and when on plane about 14 knts. Bob from Cat came over about a month ago and said its not an engine problem it was likely props. Thats when owner had boat pulled and all the bottom work done. The bottom was painted, new cutlass bearings, props pulled & scanned by General Prop, rudder and trim tabs both check okay. Put back in water and still same problem. The engines will get up to 2200+rpm and boat will be struggling trying to get on plane. Any ideas on what the issue could be.
  2. NYCAP123

    NYCAP123 Senior Member

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    Tabs could be an issue as could weight distribution, but I'm inclined to think the hull has absorbed water. Were there blisters when he hauled?
  3. Pascal

    Pascal Senior Member

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    Did they check the weight in the slings? I doubt blisters can carry enough water to make a difference...

    Twin 700hp should be plenty... heck my old 53 Hatteras gets in plan early with twin 435 6CTAs and she s no lightweight either.

    unless there is a ton of weight in the back of the boat, with clean running gear and working tabs, that thing should plane easily. Sounds like an engine issue to me.
  4. NYCAP123

    NYCAP123 Senior Member

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    He said the motors and running gear have been checked and that the motors are making correct RPMs. I'm thinking about blisters as an indication of a bigger problem. At 8.6 lbs. per gal. a 53' hull that's absorbing water could get very bogged down. My next question for the OP is how long was the boat in the water prior to this haul. I suspect a long time. I'd haul again and put a moisture meter on the hull and keel.
  5. Beau

    Beau Senior Member

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    You say it used to get up on plane at 14 knots. Did the problem arrive all of a sudden? If so, did the owner change anything 2 months ago? Do boats still get "hooked" transoms, I think was the expression.
  6. bayoubud

    bayoubud Senior Member

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    Probably Cat C12's, if they are max rpm at 2200 they are over propped. They should turn 2300 +. Should still get on plane.
  7. Pascal

    Pascal Senior Member

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    he also said the trim tabs have been checked ....

    unless the bottom is balsa cored I don’t see that much water getting in to the point of preventing the boat from getting on plane
  8. CSkipR

    CSkipR Member

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    I'll try to answer some of the questions.
    Bayoubud you are correct they are C12s. My mistake. The max rpm is 2300 and they will turn that I was just saying it wasn't planning at 2200. We didn't go any higher.
    Beau the problem did arise all of a sudden. The boat has been in the water since he owned it other than for a haul out once or twice. Trips to Keys & Bahamas last two years. The owner has not changed anything.
    NYCAP - other than the recent haulout the bottom was also painted last year. Guess it could be water in the hull although for it just to appear all of a sudden is strange. Its a 2003 boat. No known blisters.
    Pascal - the scale was broke when boat was hauled so we did not have the weight. Suspect around 80k. In order for the boat to plane the tabs have always had to be all the way down.
  9. NYCAP123

    NYCAP123 Senior Member

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    Because the tabs are working doesn't mean they're working right. He mentioned that they have to be "all the way down" to get on plane. Just a little low on fluid could keep this boat from getting on plane.
    I believe the hull sides are cored. Not sure about the bottom. Blisters would be a symptom, but no blisters doesn't preclude a wet hull. When we did Valhalla's bottom after 6 months in a climate controlled building with lamps on the hull it was still wet.
    I believe the specs say the weight is 60,000 lbs.
  10. Capt Ralph

    Capt Ralph Senior Member

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    What does the % of load say?
    Maybe some fuel flow data also.
  11. CSkipR

    CSkipR Member

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    NYCAP agree on the tabs although alot of pressure was applied when they were down as well as up. Fluid is full. I believe that weight for dry hull is correct. With 1000 gal fuel, 300 gal water and extra 25kw generator and alot of misc it is a heavy boat.
    Capt Ralph - before the issue the load was 80% at 2000 rpm. Since the problem the load is actually about the same maybe slightly better at 76% since the props were scanned and balanced. Don't have any fuel flow data.

    When we ran the boat yesterday after getting it out of the boatyard it did the same thing it was doing when we took it in with the problem. Up until this problem the boat has been run weekly to keep the bottom clean when this issue developed.
  12. PacBlue

    PacBlue Senior Member

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    Sometimes when they paint the bottom and use the wrong roller the paint gets “stippled” and is too rough of a surface, resulting in more drag and lower performance. Have had to have a few sand smooth to get it back to where it was at.

    The other thing is to get into deeper water, at least 30 - 50 feet before making any final assessments.

    At 2200 rpm, they may have scanned and reconditioned the props, but they have too much pitch. It is out of spec for a C12.

    Have had some luck in taking out pitch and adding cup to get more stern lift, but that is a trial and error game if you haven’t done it before.
  13. Capt J

    Capt J Senior Member

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    They don't get on plane. I ran a 66' offshore with 1000 hp C-18's and it was the same way. It did do 14.5 knots but HAD to have over 10' of water under her keel.....15' or deeper, depths......horrible bottom design......in the intracoastal she wouldn't do more than 7.8 knots.....no matter how much power you poured on. At 80% load she was at 7.8 knots, bow up at a 30 degree angle and throwing 6-7' rolling waves even with the side of the boat.
  14. Capt Ralph

    Capt Ralph Senior Member

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    One last thought here, How deep is the water your trying to run in?
    Been on a few boats that will not level out with less than 20 feet under them.

    I can tell it's getting shallow on our Bert, bow starts coming up under 15 feet.
  15. Pascal

    Pascal Senior Member

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    I routinely get on plane in 9’ of water. Both my own 53 hatt with the 435hp Cummins or the 84 lazzara I run (C32s). Before that the Johnson 70 with 3412s... the shallow water was never an issue.

    the only time i feel the shallow water is at hull speed. Loose about a knot but as soon as the power comes on, the boat pops on plane
  16. CSkipR

    CSkipR Member

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    PacBlue - no its not the bottom paint it did it before it was hauled and repainted. Yes we ran ran it outside and inside trying to get on plane. On the props it did it before and then after the props were scanned. They were scanned and tuned after the haul out but the problem started previously before this was done.
  17. CSkipR

    CSkipR Member

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    Capt J it has always been able to plane at 14 knts with trims full down. He runs it in the intracoastal as well as offshore at 14 knots. The boat now when trying to get up will start shuddering when it gets close to that plan speed. Kind of like you would have an prop with a bent blade except rpms and load are pretty normal.
  18. CSkipR

    CSkipR Member

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    He spoke to someone late yesterday from Offshore and they told him to check a section of the hull for water. Supposedly there is a pocket on the outward side of the hull that water could leak into when filing water tank.
    Thanks for all the feedback will let everyone know when the issue is found.
  19. bayoubud

    bayoubud Senior Member

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    Is the boat stabiliized with fins?
  20. CSkipR

    CSkipR Member

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    Yes it is.