Has Anyone ever tried Moving the outdrive back ?

Discussion in 'Boat Design' started by Doodler 2, Jan 20, 2018.

  1. Doodler 2
    Joined: Jan 2018
    Posts: 18
    Likes: 0, Points: 1
    Location: Oregon USA

    Doodler 2 Junior Member

    And leaving the motor where it is?

    like in adding a hull extension, with swim platform, and the outdrive on the relocated transom,
    and using a drive shaft to connect the motor to the outdrive.

    As opposed to adding a hull extension, with swim platform, and adding a new or newer outboard.

    In case someone might ask why I would consider something like this:
    To use my existing boat.
    Gain more WL length
    use exsiting outdrive.
    Help move the balance of weight forward.

  2. Barry
    Joined: Mar 2002
    Posts: 1,812
    Likes: 465, Points: 83, Legacy Rep: 158

    Barry Senior Member

    reading between the lines as you have not supplied much information
    Your boat is a planing boat with an inboard outboard?
    If it is a Volvo, they had or still have a remote outdrive/ leg that you can run a jack shaft from the engine to the leg.

    And you are trying increase the wl why?
  3. Doodler 2
    Joined: Jan 2018
    Posts: 18
    Likes: 0, Points: 1
    Location: Oregon USA

    Doodler 2 Junior Member

    This an old Fiberform, 1971, using chevy st.6, and Mercruiser outdrive.
    Everything has been done on a very low budget. As detailed on "Another first post" , here in Community forum.

    As I have added LOTS of weight, the hull sinks deeper, as expected.

    Already have a swim platform, supported by struts.
    The idea of adding a hull extension, and a new or newer 150 hp outboard is not new, and was considered when viewing a Bayliner for sale
    on Craigslist that had been set up that way.

    Reasons Why:
    When floating at dock, boat sits level, swim platform 6" above waterline, when both of us are standing on the platform, or at the back, like
    when landing a fish, the platform is level with, or under water. :: Extra Flotation.

    When running around hull speed, around 7.9 in MPH, the stern is already starting to squat, as expected. From what I have read, any extra
    WL Length will help the squat and increase the speed a bit. Possible help mileage a bit.

    While this boat will get on a plane, and hold it around 21 MPH, (reading from GPS) it needs to really work at it. Having 2' more of WL and flotation
    at the back, then adding some trim tabs, should help a bit.

    My wife does not care a bit about what she calls "Zooming Around" and is fine using the 10hp trolling motor, at about 1mph, and is OK with
    using the outdrive at around 8mph, not knots.
    As expected hubby feels the need to "get back to the dock" before midnight. We always seem to end up at the "far end" just at sunset.
    What we have works for us, but I know the old motor/outdrive is straining when on a plane.
    So staying around the same planing speed, but without as much strain would be one goal from adding the extension.

    The other ideas we have been discussing from the start are age of the power unit and cost.
    I see having a new or newer outboard hanging out back as a safety feature, even if I don't like the way it looks that much.
    There is also a possible safety feature of "not having your boat staying afloat by way of rubber boots." If an outboard quits, at least the boat
    might still float.
    While the bellows are newer, that is not much to keep back the flood.

    Than comes cost, and is the main reason for using all the old recycled boat parts.
    After parting out 5 boats for this build, I had 4 outdrives, transom brackets, and old broken 250 ci chevy 6's for parts.
    The 292 -6 i'm using came from a wrecked PU, and had not been in a boat before.

    So the first choice for repower might be an extension with a new 150 hp 4-stroke outboard. My wife loves the boat we have built, and does not
    want another one. That's good, it's already paid for.

    So the second choice might be an extension with a used but newer out board. Still over out budget, but possible later.

    That leaves the third idea, of using what I have, but gaining any advantage of a bit more length, and flotation.
    Making that change will be expensive, and take some time. Means longer control and steering cables, relocating the trim/tilt unit, fabricating
    a new drive shaft, possibly with an added pillow block bearing, finding yet another old junk boat to "rescue" the transom from, and down time.

    Sounds like a waste of time. Might be. Still, I have some skill and experience fabricating, recycling, using what I have, and taking on crazy projects.
    And not much money to sink into a nearly 50 year old boat.

    i have mentioned before to my dearly beloved that we can buy some fish down at "Ray's Food Place".
    But she loves the time spent floating around as much as eating her fish. Did I say yet that she does all the cleaning, smoking, and cooking?
    The smoked salmon dip she makes is a BIG hit, wherever she takes it.

    I get to play around with the boats.

    Lots of words here. Hope this explains why I would ask if anyone else has moved and out drive back, before I think seriously about doing so.

  4. Barry
    Joined: Mar 2002
    Posts: 1,812
    Likes: 465, Points: 83, Legacy Rep: 158

    Barry Senior Member

    Do you feel that the freeboard when you are at the back landing a fish is too low?
    If this is the only reason for the hull extension and subsequent work is to get the swim grid higher in the water, a low swim grid may not be a safety issue.
    If you feel the engine is "working to hard" at your desired cruise speed, get it reworked. The 250 can put out horsepower easily up in the 200 - 250 range. Lots of info on this
    You might have to buy a new prop but this is small change.
    And cheaper than trying to split the engine and drive and all the other mods necessary to get the swim grid up a few inches, if the boat is safe at the level that it is at.

    Alternatively, extend the hull, move the engine and drive back and don't target running the boat at the "hump speed" ie high bow up angle. This is not an fuel efficient, mpg,
    speed for any boat.
  5. Doodler 2
    Joined: Jan 2018
    Posts: 18
    Likes: 0, Points: 1
    Location: Oregon USA

    Doodler 2 Junior Member

    The freeboard is fine. I used the fiberglass panels saved from the parted out boats to raise the deck, and freeboard all the way around.
    Now have two deck seams, and matching rub rails, and high freeboard.
    Having the platform in or at the water in fine, as long as the transom door is left closed. Not built to be an offshore boat.
    useing the swim platform for reference point only.
    When on plane platform is out of the water.

    I am not using the 250. Am using a 292, which is identical, but with a longer stroke. I trust this engine enough to use it the way it is, and
    ran one in my own old pickup for 20 years, before installing a 350. The 292 has more torque, and still turns 4,000 rpm ok.
    Cost was a big factor with this motor. I got it back for next to nothing. Paid $100 for it many years ago, pulled it out of a wreck to use
    in a truck, didn't use it then, bartered the motor for a welder. That friend didn't use it for his forklift, like he thought he would, and stored
    it inside, in a dry place.
    Then when I needed a motor for this boat project, I bartered a helm, controls, cables and other parts from the boats I took apart,
    to get the motor back.

    Bought the new prop already. it was a big help. Won't be running "on the hump".

    Have access to "hot rodding" tips and help, but these days rebuilding can cost more than a running engine.

    The safety issue I was talking about was the rubber boots and or bellows that all out drives use, and how mounting an outboard
    eliminates those possible big leaks.

    I understand that almost everything about boats is a trade off. Don't really like to see a big motor hanging off the back, but modern outboards
    have some good advantages. One being able swap out the older one for a newer one. That brings up cost again. The old inboard/outdrive system
    is what was on hand to use.

    So the hull extension idea was mainly for performance and weight balance, not safety.

    As mentioned, a first choice, if changes are made, would be an extension with new outboard, for performance, but also dependability.

    That first choice is way out of our budget. Even a used late model outboard would need to wait a few years'

    Moving the currant motor/outdrive together is not an option. That would mean building a longer boat.
    The hull extension would leave the hull "as is" and adding a store bought extension, or the last 2' of another old boat bolted and reinforced
    on to the back of the boat, but no higher than the swim platform, and not increasing the 'Assigned" boat length.

    Thanks Barry, for replying. hope I've not used too many words to say too little, but posting and discussing boat talk sure beats gardening in
    the rain.
    Also considering making changes, and discussing possibilities beats making mods and finding out they don't work.

  6. Barry
    Joined: Mar 2002
    Posts: 1,812
    Likes: 465, Points: 83, Legacy Rep: 158

    Barry Senior Member

    I have only owned a couple of Inboard/outboards and was told by my mechanic that even if the bellows rip, no water gets into the boat. Only in the short drive shaft area
    Perhaps others can confirm. Volvos, one gas with Aquamatic 260 or something like that and 2 diesel driven DPH-A

    Rebuilding might cost more than a new engine but your earlier post said that the engine was straining to cruise. So a relatively cheap rebuild, porting, cam designed for more HP in your cruising range, better carb distributor etc, Maybe 3500 US funds? Whereas a new bobtail might cost about the same but only similar HP

    I assumed earlier that when you said hull extension, that you were meaning extending the hull, taking out the old transom etc. Not an add on somewhat extraneous to the existing hull

    Perhaps someone can offer a more learned opinion as to the fact that if a bellows leaks, you get water into the engine compartment.
  7. Doodler 2
    Joined: Jan 2018
    Posts: 18
    Likes: 0, Points: 1
    Location: Oregon USA

    Doodler 2 Junior Member

    Thanks for your reply,
    I will welcome any opinions, or facts about water getting in when bellows rip or crack.

    My concerns came from seeing the path for water, through the transom plate, where the drive shaft goes through, that is open to the inside
    of the bellows, when assembling, and from reading in the repair manual that clearly states, "do this, or water will get in"

    My other boat has OMC, no hiding the big rubber boot there.

    $3,500 to rebuild, and soup up the old 6 is most likely close. The friend ,who I bartered this engine to and back from, used to build stock cars.
    He took an old 292- straight 6,- cut out the obstructions in the head where the head bolts go through, plugged the holes on top,
    used short bolts, reached through the intake ports, for the head, a simple hand polishing, and blew away all those other pumped up 350's
    that cost $20,000 to build. At least until a rod let loose. Just a fun experiment.

    Back to the boat. This boat has been built on a very narrow budget. Have only spent $4,000 so far, including trailer and tags. Goal was $5,000.

    My guess for an extension was around $500, by using the back part of a discarded boat, plywood, mat, and polyester resin.
    Not counting any labor, that is what I have to add.

    Also guessing, a used, but newer 150hp, 4-stroke to be around 8 to 15 grand, unless you have one for less.

    And what does a brand new 150 or 175 go for?

    As for the "moving the outdrive" back, and leaving the engine where it is, i was guessing at $500 for extension parts, and another 5 to 8
    hundred for longer cables, driveshaft/bearing, and some kind of watertight hatch to install on the swim platform to gain service access to the
    new used transom plate, steering and shift cables. That puts the possible total to around $1,200, and back in the budget.

    I am able to do at least some of the machining , all the cutting and fitting, and tweaking .

    While I am a new guy here at this forum, I am closer to 70 than 50. Been through lots of "Questionable" projects, no need to stop now.

    We get a lot of mileage from used parts. I would still like to know if anyone else has tried moving "just the outdrive'

    I have seen one 25' boat set up with an outdrive and a small diesel set way forward, like an inboard. No transom extension,they used old transom.

    Barry, did you check out the "Another first Post" thread ? There is enough there to put this project in perspective. It's down in Community ,
    Every Thing Boating.


    PS what a great website, I love the pictures. Everything I can think of, about boats, has been tried, built, or designed and posted here.
  8. Barry
    Joined: Mar 2002
    Posts: 1,812
    Likes: 465, Points: 83, Legacy Rep: 158

    Barry Senior Member

    I did not read the other thread
    You can Google Volvo Penta Jackshaft for info on what Volvo does. Evidently there is a kit available for that so you might see what the components are
    Do Sterndrives ( bellows) sink boats? is a 2009 thread, just found it, one guy says Volvos no, mercs yes
    so I am not at all sure

  9. Doodler 2
    Joined: Jan 2018
    Posts: 18
    Likes: 0, Points: 1
    Location: Oregon USA

    Doodler 2 Junior Member

    Volvos are very high priced. one friend paid over $ 2000, for a 4cyl rebuild, and the head was good, had already been rebuilt,
    Then there's Myron, who has a 28' Bayliner with a volvo 280,and volvo diesel. Unbelievable prices for parts. More to rebuild the motor than the boat
    is worth.
    Then there's friend Jerry, had a volvo sports wagon,all wheel drive, they wanted $15,000 for a "rebuilt" transmission,
    they finally bought a used, but working, tranny, for $7,000. Had a one month guarantee, not including labor.

    Thanks anyway, someone else can have the volvo.

    I am searching for the thread you mentioned. kentr
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.