Click for Westport Click for Comfort Click for Nordhavn Click for Ocean Alexander Click for Mulder

Yard to do Strut replacement for Aluminum Hull

Discussion in 'Technical Discussion' started by jhall767, Oct 9, 2013.

You need to be registered and signed in to view this content.
  1. jhall767

    jhall767 Senior Member

    Joined:
    Jan 14, 2010
    Messages:
    319
    Location:
    Middle River MD
    I'm looking for recommendations for a yard to replace the struts on my 44' Striker. I'm located in the Baltimore area so I'd like to start there but the boat is operational and would consider taking it somewhere if the quality of work justifies it.

    I'm looking to increase the shaft size on the boat as it is marginal at best. This could either be done by replacing the sleeves that hold the cutlass bearings or replacing the entire struts. Currently they are V struts and I would like to consider P struts for less drag and turbulence. There is a small V strut about 12" from the shaft log and another V strut at the propeller. The boat currently cruises at 21 knots. At that speed the shafts are turning 1050 rpm. Swinging 26 x 30 nibral 4 blades.

    Thanks

    John
  2. CaptGDunz

    CaptGDunz Member

    Joined:
    Mar 24, 2009
    Messages:
    60
    Location:
    Jersey Shore (North)
    Yank Marine, Tuckahoe, NJ
    Derecktor, Mamaroneck, NY
    Ocean Marine, Portsmouth, VA

    Sorry, no experience with that in Baltimore.
  3. Yachtjocky

    Yachtjocky Senior Member

    Joined:
    Oct 17, 2010
    Messages:
    365
    Location:
    Fort Lauderdale
    Struts

    How old is the boat

    How many shafts have you gone through.

    Stick with what you have
  4. SeaEric

    SeaEric YF Historian

    Joined:
    Jan 28, 2007
    Messages:
    1,360
    Location:
    out on the dock
    Deckelman's in Rock Hall can probably do it. I'd also call Anchor Bay in Baltimore. They seem to be able to do most everything.
  5. Capt J

    Capt J Senior Member

    Joined:
    Jul 11, 2005
    Messages:
    14,432
    Location:
    Fort Lauderdale
    This. Or, I worked on a 75' Jim Smith SF and it only had 2.5" shafts for 2000hp engines. This was because they were splined and didn't have the traditional keyway making them much stronger.
  6. jhall767

    jhall767 Senior Member

    Joined:
    Jan 14, 2010
    Messages:
    319
    Location:
    Middle River MD
    NJ and Portsmouth are only a long day's run away. Been past Ocean marine at least a dozen times. Seems like I'll need a yard that does commercial vessels / large yachts.

    Thanks
  7. jhall767

    jhall767 Senior Member

    Joined:
    Jan 14, 2010
    Messages:
    319
    Location:
    Middle River MD
    Boat is a 1970. Shafts and struts are at least 25 years old. So yes they have been ok for awhile. Struts appear to be out of alignment based on wear on cutlass bearings and difficulty in turning them. Have been through at least one hard grounding that bent everything up. So I'd like to get them checked/realigned at a minimum. Since everything is welded in place I need a yard that knows how to replace welded struts.

    As to upgrading. I have 450 hp 671ti's running through 2:1 twin disc transmissions to 1.75" shafts. 26" props. Fine or barely large enough?

    If they have to cut the cutlass bearing housing off and re-weld it then I'll have them go up one size in the housing. Still will be able to use the current shafts just switch from a size "GLENDA" to a size "GLORIA" which has a larger outer shell. This will allow me to increase the size of the shaft in the future (repower) without reworking the struts again.
  8. jhall767

    jhall767 Senior Member

    Joined:
    Jan 14, 2010
    Messages:
    319
    Location:
    Middle River MD
    I've had a lot of work done at Anchor Bay East. Very competent but they don't (or didn't) have a welder who was experienced with boats. Might try Deckelmans. Was by your home marina on Saturday buying gas for our little boston whaler.

    Thanks
  9. Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    12,647
    Location:
    Satsuma, FL
    1 3/4" shafts should be a good size for you. The material of the shaft is what you need to be checking. The strengths and safety factors vary greatly from mfg to mfg and then different levels from the same mfg.
    Do you have any documentation on your shafts? Something like Aqua-met 22 or similar phrasing in any past notes , brochures or receipts?

    A complete inspection by a correctly equipped shaft shop could also be of benefit.
  10. jhall767

    jhall767 Senior Member

    Joined:
    Jan 14, 2010
    Messages:
    319
    Location:
    Middle River MD
    I have the shafts pulled and checked/straightened every two years. However I have no idea what the material is. What would they have used in 1988? I have been told by more than one professional shop that 2" aquamet 22 would be required to get me close to the recommended safety factor of 5. Also that 1.75" is below the recommend size shaft for a 26" prop and is the absolute minimum that michigan wheel will sell. Are they right? Who knows? Do I need the safety factor of 5? Is just over 2 ok? If I have to keep the 1.75" shafts I will definitely go with the high strength material.
  11. CaptGDunz

    CaptGDunz Member

    Joined:
    Mar 24, 2009
    Messages:
    60
    Location:
    Jersey Shore (North)
    Here is an easy way for you to check the shafts yourself: Take a magnet in the engine room. Hold it against the shaft. If it is Aquamet 17 the magnet will stick. It will not stick to Aquamet 22. If you're going to repower in the future with higher horsepower, increase the shaft size and strength.
  12. NYCAP123

    NYCAP123 Senior Member

    Joined:
    Mar 14, 2008
    Messages:
    11,205
    Location:
    Long Island, NY
    Call Mike's Mobile Marine Service 7629 Water Oak Point Rd
    Pasadena, MD 21122 Phone: 443-463-2820
    He can't do this job, but I had him do an emergency repair on the Hat recently and I'd trust his local recommendation.
  13. Capt J

    Capt J Senior Member

    Joined:
    Jul 11, 2005
    Messages:
    14,432
    Location:
    Fort Lauderdale
    Pulling the shafts every 2 years, if you've had no damage to the props is quite eccessive. 5 years is a good number. I wouldn't change anything right now. Have the shafts/struts aligned and leave everything else alone. Have the shafts dial indicated on the boat. If it lasted 25 years, it's fine. If you add more horsepower, keep the same shaft size and go to stronger splined shafts.
  14. Bill106

    Bill106 Senior Member

    Joined:
    Jan 9, 2010
    Messages:
    390
    Location:
    Beaufort NC
    After doing several refits on aluminum hulls I've had my eye's opened on how the "metal half" lives and goes about handling pesky issues like shaft alignment and such.

    In Fiberglass or wood construction, you have to nail the shaft line down when you install it and struts are bedded in to be within normal tolerance (.003" at the coupling end and no appreciable rotational resistance aft), all with cutlasses tight in the shaft log and strut. Of course some boats experience sagging or hogging when blocked vs. in the water but a short period ITW and a second check/alignment usually takes care of it.

    Aluminum (and maybe steel?) boats seem to have a different approach. Their struts are usually overbored and a quad of setscrews on either end of the strut bore is used to align the cutlass bearing and a potting compound of epoxy is used to make up for whatever difference in alignment is present. Once the compound is cured, the set screws are removed and the project is finished.

    If you have a reddish orange compound surounding your cutlass bearings you most likely have the same situation and need to completely remove it, drill and tap for set screws, align and pot the bearings in. The better companies doing this use laser targeting. Your shaft size sounds fine for the horsepower.
  15. jhall767

    jhall767 Senior Member

    Joined:
    Jan 14, 2010
    Messages:
    319
    Location:
    Middle River MD
    The shafts are pulled after "events" or when we're experiencing vibrations. "Events" seem to happen more frequently on the Delaware River. I do the work so it's pretty cheap to have them tuned up. Managed to hit some submerged railroad ties this year:(

    The cutlass bearings are just pressed in. Not set in any epoxy. They are showing uneven wear and I'm getting vibrations. At this point I want the alignment checked by someone who can also fix it.

    I'm going to check the shafts to see if they are magnetic or not.

    Has anybody switched from V struts to P struts? Any real benefits?

    This site is great !
  16. Bill106

    Bill106 Senior Member

    Joined:
    Jan 9, 2010
    Messages:
    390
    Location:
    Beaufort NC
    A very tight string and some disks can be used to check coarse strut alignment but are not so precise when looking for slight off axis errors in a bearing. We have found a laser setup to be much more accurate and you can shoot from both ends of the drivetrain to check how things are aligned.

    I misspoke earlier when I said your shafts are adequate. I ran a quick calculation using Western Branch Diesels "The Shaft" size calculator. You always use WOT rpms, and with it you only have a safety factor of 2.591 with Aquamet 19 shafting and 3.182 with Aquamet 17/22. A safety factor of at least 4 is very desirable for your situation.

    Here's a pic of our kit for shaft laser alignment, a set of inserts machined for different size bearings with a hole bored for a calibrated laser pencil to shoot the beam. It does require removing the shafts but it sounds like you need to do that anyway.

    Attached Files:

    • 001.jpg
      001.jpg
      File size:
      70.9 KB
      Views:
      656
  17. K1W1

    K1W1 Senior Member

    Joined:
    Sep 30, 2005
    Messages:
    7,388
    Location:
    My Office