Can i replace Inboard with Outboard on shaft

Discussion in 'Inboards' started by Brian Blake, Dec 26, 2017.

  1. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Rafting is as simple as it sounds, you tie the boats together, using straps, lines, fenders, etc. as you feel necessary. Freeboard isn't much of a problem with this method, as you just fender off everything. I like to use a ratcheting strap to cinch the hulls together, usually around the lower sheer, angled up to get a good purchase on the bigger boat. A line or two tied to the strap can keep it from sliding down the larger hull. If you use lots of lines, the loads on each cleat decrease dramatically.

    I'm not sure what you're attaching that bracket to, but it better be stiff and strong. Even small outboards, can develop a surprising amount of torque and twist off things not well attached. I thought your tow boat had a 70 HP or bigger engine on it. If this is the case, you'll have a much faster and better ride, than rigging up a dinky kicker and putter along at walking speeds. Additionally, with the tow boat's bigger engine doing the work, currents, winds and other things that make this difficult will be decreased, as you'll have sufficient reserve power to punch through chop, etc. In short, I think you're over thinking this problem. Towing, by a line or by rafting isn't a complicated thing. A line tow is as simple as it gets, though you lack some control, just going slow will usually make the deal uneventful. Rafting offers more control, though you'll have to position lines, fenders, etc. until you can drag her with reasonable authority and steering control. Where to place these lines and making adjustments to them becomes quite obvious once you start out. I like to have the tow boat slightly aft of port midship on the boat being towed, which places it's bow pointed to port. This puts the tow boat at a natural angle to pull to port and you'll be facing, port to port overtaking, so you can see what's ahead. Down there you may prefer starboard to starboard over taking, so rig the boat on the appropriate side. With the tow boat "canted" to the side a little, the drag of the boat being towed, will be offset by the thrust of the tow boat's outboard, making steering a little easier.
     
  2. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    The duckboard looks weak.

    The prop of the reserve/kicker will be awful small so no torque.

    I’d try a couple junk tires as fenders and rafting would be the first try.

    You need the other boat one way or another and that lottle kicker is going to be pushing big n towin 17.
     
  3. Brian Blake
    Joined: Dec 2017
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    Location: Auckland, New Zealand

    Brian Blake Junior Member

    Thanks All,

    Rafting it is, with an outboard for backup. I really appreciate you all sharing your knowledge and advice. Hopefully this weekend i can get over to it although it looks like mother nature may have a hand in delaying me.

    Thanks
    Brian
     
  4. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    It’s not nice to fool with Mother Nature.

    Fair seas for your plan.
     
  5. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Never allow your schedule to dictate, what mother nature has proclaimed to be a bad day. Most ill fated events are because a skipper decided they could risk it, when in hindsight, they know they should have paid attention to what she was hinting at, assuming they survived. Waiting an extra day or two is inconvenient, but the wisest choice.
     
  6. Brian Blake
    Joined: Dec 2017
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    Location: Auckland, New Zealand

    Brian Blake Junior Member

    Agreed, its blowing a gale here so will wait for a few clear days before venturing out.
     
  7. Brian Blake
    Joined: Dec 2017
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    Location: Auckland, New Zealand

    Brian Blake Junior Member

    Ok, so after a very adventurous morning we abandoned rafting and went for a simple old tow. We waited for Mother Nature to do her thin and boy did she turn on the perfect day for it, the water was like a pond. The tow back was loooong slow and bloody tiring but the old girl is now safely moored at the new marina ready for a bit of TLC.

    I haven't got any more useful engine info, other than the crank seems jammed. Even with a socket and power handle on the crank pulley i cant generate any movement, the gearbox seems willing when the starter is fired, the engine not. So i'm going to go with Seized, but in a few weeks i'll bring it up on the hard and start letting the professionals loose on it. Assuming it is seized i don't think i'll rebuild it as it looks very "patched up" and research online indicates it is a fairly rare engine as well so parts will not be my friend i expect.

    I have a question now about engines and power setups as i'm starting to make plans in that regard.

    I have an option on a 220 ci Chevy Short Block with transmission, prop and propshaft (although i wont use the shaft) for a pretty good price and history. My research tells me it will turn up a little short of 300hp at the flywheel then through the 25:1 gearbox to the prop. This is nearly twice the suggested horsepower (so am i over cooking it?) but to me suggests i would never even have to stretch its legs to get a good pace going, my worry then is i'm probably running 2 cylinders i don't need and could well be setting myself up to be mugged by petrol companies every time i want to go out (thoughts?). I want to do some overnight and weekend (but not necessarily speedy) trips on this boat so running costs is a consideration, as is reliability. On the + side for the Chevy, i know those engines inside out and upside down, so i personally am more confident in trouble shooting if necessary, but its a minor consideration. The engine comes straight out of another motor cat (one of a pair) and will include right down the prop (no idea of condition yet), gearbox and everything needed to re-power mine albeit with a few more ponies.

    In the video below, is it possible to tell by the "tow" stance of the boat if its likely to plane? The buzzer you can hear is an intermittent fault my fizz developed on this trip of setting off the low oil alarm which has now been fixed by my local motor guy, so speaker off is recommended. The video was filmed doing around 4.5 knots.



    I do also have options on some Nissan Diesel Turbo (SD28 etc) engines but at only around 120hp i'd like to plane it if possible and they don't have transmissions with them. If it is a displacement hull then am i right thinking the 120 is probably quite sensible and reliable.

    As always thanks for all the help, having it back over the harbour and moored up out of the elements is a huge relief.

    Thanks
    Brian
     

    Attached Files:

  8. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    See the tow was slow, but you managed, congratulations. I'll bet steering was a tad sketchy, but hell you made it. A good day and perfict condisions always makes things much easier.

    There has never been a 220 (CID) small block Chevy, though there has been a 220 HP 283 Chevy (V8), though these haven't been made since the mid 60's and it's a first generation small block with the inherent flaws these have. Generally, these with a typical cam and 4 barrel carb will produce about 185 HP, though up or down 10 - 15 HP is also possible, keeping within a sensible level of reliability. I also don't think they made a straight or V6 with a 220 displacement, though the 3.6 L (V6) is a 220 CID engine (actually 217), but this is a fairly modern, direct injected, double overhead cam setup, that appeared in the early "teen" years (LLT family) and has been upgraded somewhat since, then dropped. I don't know if it's been marinized, but this type of engine isn't common.

    ID the actual engine you're looking at, as a 220 CID engine wouldn't like spinning at WOT with 300 or nearly so HP for long. The previous pictures you posted didn't show much, but it did appear it was a hull capable of full plane or at least semi plane, though I thought the chine was too immersed for a semi plane design.
     
  9. Brian Blake
    Joined: Dec 2017
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    Location: Auckland, New Zealand

    Brian Blake Junior Member

    So just had a quick look at the listing.

    Both engines are Ford short deck Windsors 221ci from 1962

    My thought is to grab one and drop it with an engine reconditioner for compression checks and tidy up work to ensure its in good condition.

    Thanks for your feedback Par, thoughts on this block? It's come from a Mason Clipper (not a cat which I thought) which is slightly larger than mine but only by 3-4ft.

    Thanks
    Brian
     
  10. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    That particular engine wasn't around long, before significant changes (bell-housing, bore, stroke, internal modifications, etc.) and they're well known to not take much heat, before they spit out some parts, in a usually oily, often loud way. These produced 130 - 140 HP and were only made for a couple of years, before major changes came down. This engine eventually evolved to be the venerable 289, but it took awhile to get it refined. All (hopefully the bell housing fits) of the stuff on this 220 will fit on a 289 and you'd be best advised to just get a 298, as these are relatively cheap (many millions made, compaired to a couple 200,00 of the 220), produce more power, are more robust, etc., with many more options available, that aren't for the 220.
     
  11. Brian Blake
    Joined: Dec 2017
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    Location: Auckland, New Zealand

    Brian Blake Junior Member

    OK, so updates. I've now secured a good condition, running circa 200hp Marinised V6 Ford block which came from another 28 footer. It'll be shipped in a day or two and will then spend some time with and engine builder for a checkup and any subsequent work required. Once i have it here (its at the other end of the country, so i've taken a bit of a gamble on it) i'll be able to get the engine #'s off it for more specific info.

    In contemplating the move from Diesel to non turbo Petrol, what sort of things should i be contemplating? In my mind it seems like a gearbox, change of engine mounts & fuel lines etc and i should be off, although i'm sure its not quite that simple.

    Additionally any recommendations on Gearbox manufacturers? As i'm working on the assumption i cant use the piece on board purely because of the different mounts? But are there math equations i need to be considering etc relative to prop, gearbox ratio etc, or are they all relatively similar enough to not over think it?

    Thanks as always
    Brian
     

  12. ben2go
    Joined: Jul 2008
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    Location: Upstate, South Carolina,USA

    ben2go Boat Builder Wanna Be

    I've done this before once for a friend. You are about to spend some coin to go from gas to diesel. Everything on the motor and in the boat will have to be changed over to explosion proof. That's every piece of electrical equipment, switches, relays, starter, air filter, distributor, any electric fuel/water pumps. If it switches, pumps, or has a motor it will put you at risk of a fuel vapor fire. That brings me to bilge blowers. You will need two at least or one huge one to help evacuate fuel fumes that may accumulate in the bilges while the boat is sitting unused. I have seen so many owners blow ther boats all to hell by jumping aboard and firing up without running the bilge blowers. It happened recently here and cost a marina it's entire docking system plus about 50 boats and hundreds of millions of dollars in damages.

    Now that is out of the way. Water, you need water to cool an engine. Are your through hulls in the right place to provide cooling water? Are they big enough? IS the engine on a sealed cooling system with a engine water to fresh/salt water cooling system? Are there pumps onboard to handle the water flow? Are the pumps electric or engine driven?

    Exhaust cooling, is there a muffler aboard? Will it handle the larger engine? Can it pass the exhaust plus the water from the exhaust without compromising power? What happens if the new engine is shorter in height and the exhaust water has to travel uphill to be expelled? The engine will backfill with water when it's shut down and hydrolock the engine.

    Now about that fuel system. Are the tanks still good? Are they big enough to feed a thirsty gasser? No leaks? Are they rated for gasoline? If they are composite tanks, probably not. Are the vents large enough to prevent vacuum lock of the fuel system? Gas engines suck fuel faster than lower power diesels. Returns, are they there? Will the new gas engine need them? Are they big enough to hand the return flow? Is the system in place capable of handling gasoline?

    Now onto controlling the boat. Will the current controls connect to the new engine's throttle? Will you get full and complete travel of the controls at both the helm and the engine? Did the old engine provide hydraulic power for the steering? Can the new engine provide that hydraulic power? Will it require a new engine specific hydraulic pump and mounts with new hoses to run the steering? Will the steering station at the helm be capable of using the newer system parts without failing? If the transmission has to be changed, will the current controls have enough travel to completely engage and disengage each gear? Will the drive puck/disc have to be changed? Will it require machining? Will the shaft and prop have to be changed to match the new engine/trans power and torque curve? Will new engine beds have to be made? Will new transmission beds have to be made? What happens if the new engine requires a new location along with the transmission? Shaft angle is set. Everything else around it has to line up or move the make the new power system mate up. Will the cover and hatches still fit after the conversion?


    Doing conversion can get complicated real quick. It is expensive and more so if you're working with the wrong shop/people that don't understand and know how to do these things. My first, last, and only time doing it took almost a year with my friend providing me with all the right parts for the job. I was a young person full of life back then and it still nearly whipped me.
     
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