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  1. #1

    WTH do I do with this?

    My 55c was missing 200-250 RPM's under load, heavy soot on
    transom and the horizon. Had props pulled, shop calls to inform the port wheel is 27x28, the starboard 27x30. I did note the starboard was slower to accelerate, by tach, but at wide open port was 2100, starboard 2150. Recommendations on where to go with these

  2. #2

    Re: WTH do I do with this?

    take both to 27x29 ?
    FTFD... i drive a slow 1968 41c381

  3. #3

    Re: WTH do I do with this?

    didn't you just buy this boat?? ....and talk to a prop shop and other 55C owners before changing anything . I would think you need to get rid of pitch on both to get 2350 rpm. I thought each inch = about 50- 100 rpm at WOT?? .....Pat
    Last edited by doc g; 08-15-2017 at 01:55 PM.

  4. #4

    Re: WTH do I do with this?

    Quote Originally Posted by doc g View Post
    didn't you just buy this boat?? ....and talk to a prop shop and other 55C owners before changing anything . I would think you need to get rid of pitch on both to get 2350 rpm. I thought each inch = about 50- 100 rpm at WOT?? .....Pat
    they are at the shop, they discovered the difference. It's just weird that the 27x28 only reached 2100, the 27x30 2150, the bigger prop spun up higher

  5. #5

    Re: WTH do I do with this?

    Did you verify that your tachs are accurate?
    --- The poster formerly known as Scrod ---

    I want to live in Theory, everything works there.

    1970 36C375

  6. #6

    Re: WTH do I do with this?

    If that's so I would suspect engine issues, the "under"- propped side could be pulling the "over"- propped side down(rpm -wise) too, why would you not have the same props on both sides????
    Last edited by doc g; 08-15-2017 at 03:02 PM.

  7. #7

    Re: WTH do I do with this?

    Quote Originally Posted by ageless View Post
    My 55c was missing 200-250 RPM's under load, heavy soot on
    transom and the horizon. Had props pulled, shop calls to inform the port wheel is 27x28, the starboard 27x30. I did note the starboard was slower to accelerate, by tach, but at wide open port was 2100, starboard 2150. Recommendations on where to go with these
    You using a really good prop shop? A good prop guy has forgot more than we'll ever know. If you're not sure, put the job on hold until you have confidence in them or find someone else. I grabbed my props away from the best guy around in Ft. Meyers when I found out he was the best guy around on outboard props. The boatyard made a recommendation on what was in their best interest and not mine.

    Don't worry too much about other 55's. Tell the prop shop what your expectations are relative your concerns. Ask them if they think they can achieve the goals. Settle on an agreed upon level, and ask what happens if the performance falls short.

    The minute you tell them how you want your props pitched or balanced or cupped is the point where you absolve them of any responsibility other than doing exactly what you told them to do.
    Semper Siesta
    Robert Clarkson
    ASLAN, 1983 55C #343
    Charleston, SC

  8. #8

    Re: WTH do I do with this?

    Quote Originally Posted by ageless View Post
    My 55c was missing 200-250 RPM's under load, heavy soot on
    transom and the horizon. Had props pulled, shop calls to inform the port wheel is 27x28, the starboard 27x30. I did note the starboard was slower to accelerate, by tach, but at wide open port was 2100, starboard 2150. Recommendations on where to go with these
    First off. 55C's came from the factory with 32" wheels. So the mystery deepens as to why your WOT RPMS are low.
    What HP are your 1271's? How many hours on them? Do you know when was the last time the timing was set and the racks adjusted? Lots of things play into low RPM's other than the props.

  9. #9

    Re: WTH do I do with this?

    Quote Originally Posted by mykim View Post
    First off. 55C's came from the factory with 32" wheels. So the mystery deepens as to why your WOT RPMS are low.What HP are your 1271's? How many hours on them? Do you know when was the last time the timing was set and the racks adjusted? Lots of things play into low RPM's other than the props.
    Deeper still. My owner's manual shows 30" props. I believe majority of the 55s were, as you say, 32" with Allison 2:1 gears adverting 650HP. Mine is ZF 1:1.51 with original rating of 850HP. There's at least some justification for Ageless' 28" wheels. PO of mine left me with a set of 28s. Said it jumped up on plane but lacked the top end of the 30s by a knot. Loooots of variables. Anyone looking for a nice set of balanced 28 X 28s?
    Semper Siesta
    Robert Clarkson
    ASLAN, 1983 55C #343
    Charleston, SC

  10. #10

    Re: WTH do I do with this?

    Quote Originally Posted by mykim View Post
    First off. 55C's came from the factory with 32" wheels. So the mystery deepens as to why your WOT RPMS are low.
    What HP are your 1271's? How many hours on them? Do you know when was the last time the timing was set and the racks adjusted? Lots of things play into low RPM's other than the props.
    my manual reflects 30" wheels from the factory, which are likely the extras in the ER.

    1271's are 850hp, ZF 1.51:1, 1500 hours, 2012 on timing and racks

    I agree with the other factors, thought I was being guided by a knowledgable individual
    Last edited by ageless; 08-15-2017 at 09:58 PM.

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