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Thread: Repower options

  1. #1
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    Default Repower options

    I have a lovely '39 30 foot ex forestry cruiser I want to restore, and it has the original 50 hp Universal Superfour. The engine needs some work, and although I'm sure I could get it running again, I'm thinking of other repower solutions. I'm not fond of the diesel option due to cost, noise and smell, and as low HP inboards are as a rare as an honest politician I'm wondering about retrofitting an outboard. Of all options it seems the simplest and least expensive, but of course the aesthetics might be strange having an outboard hanging off a 30's cruiser (with a lovely bright transom). Other than being ugly as sin, what other concerns should I look at, where does one start in such an effort? The current setup is not ideal with the motor right amidships and taking up space in the galley etc, and from a convenience standpoint it would be far better having it further back in any event.

  2. #2
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    Default Re: Repower options

    One thing you want to have a good handle on before you hang and outboard on the stern of a boat is to consider its pitching motion. A lot of older displacement hulls don't have a lot of bearing aft, and in a short steep head (or stern) sea they can pitch an outboard right underwater. And there goes your cheap and simple.
    If you want the machinery out of the cabin, you might consider an I/O drive. My personal favorite are the older Volvo units based on the Volvo B23 gasoline engine, also seen in the ageless 240 model line. Nice engine, good outdrive, expensive parts.
    There are a lot of modern diesel engines out there that aren't all the noisy, don't smoke. Expensive? So's any reliable engine. My pick of the litter would be the Kubota/Beta marine conversion. Probably not as good an engine as a Yanmar or Mitsubishi/Westerbeke, but you can buy almost all the parts from your local Kubota tractor dealer.
    Putting the engine and gear right aft may change how the boat trims, and her pitching moment. There's a reason the used to concentrate weight amidships...

  3. #3
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    Default Re: Repower options

    Quote Originally Posted by seo View Post
    One thing you want to have a good handle on before you hang and outboard on the stern of a boat is to consider its pitching motion. A lot of older displacement hulls don't have a lot of bearing aft, and in a short steep head (or stern) sea they can pitch an outboard right underwater. And there goes your cheap and simple.
    If you want the machinery out of the cabin, you might consider an I/O drive. My personal favorite are the older Volvo units based on the Volvo B23 gasoline engine, also seen in the ageless 240 model line. Nice engine, good outdrive, expensive parts.
    There are a lot of modern diesel engines out there that aren't all the noisy, don't smoke. Expensive? So's any reliable engine. My pick of the litter would be the Kubota/Beta marine conversion. Probably not as good an engine as a Yanmar or Mitsubishi/Westerbeke, but you can buy almost all the parts from your local Kubota tractor dealer.
    Putting the engine and gear right aft may change how the boat trims, and her pitching moment. There's a reason the used to concentrate weight amidships...
    I think that the guy was named Dave Kerr, who spoke about engine replacement, and how a hull is often mated to the torque/horsepower/weight of the existing engine. If you wanna throw all that overboard and do some outboard thingie, why not a well, north of the transom; save the mahogany.

  4. #4
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    Default Re: Repower options

    Trim was a big concern which is why I posted the idea here. New diesel (and tranny and prop and propshaft) is out of the question because of cost, and I thought a I/O were all far higher displacement and power than a 50hp 4-banger?
    I also though about a well as there are tons of unused space belowdecks aft of the wheel, and I once had a sailboat with one for the outboard that worked ok, but that was just forward of the transom itself and only underwater in a chop or when heeling, and the thought of opening up the hull further forward with a big hole below the waterline seemed like an even more extreme violation of boat design. It's true that the volume aft of this boat is much reduced compared to forward, but a 50hp 4 stroke isn't that heavy and you'd think that could be balanced by ballast in the bow? I could get a good reliable quiet outboard for a fraction of the cost of any other kind of engine refit (and far simpler as well), which is why I'm scratching my head trying to figure out a way to make it work. If it's not realistic that's okay, but I want to make sure it's not an option before trying something else.

  5. #5
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    Default Re: Repower options

    I know about outboards pitching. I had one on my Catalina 25. The boat would sail nicely but try to go to windward in anything but a flat calm to get home or get somewhere and it was pure frustration. The boat would pitch the prop in and out of the water. I burned a lot of gas and made a lot of noise for maybe one knot made good. IMHO you don't want to attach an outboard to a transom.

    Later on I repowered my 32 foot ketch. I put a Westerbeke in and really have no complaints. It's a lot quieter than the Volvo MD2B it replaced. And it's a lot lighter - something like 300 lbs compared to 500 for the Volvo. I would think any diesel today of similar power to the original Universal would take up much smaller volume.

    Any pictures of your boat?
    Will

  6. #6
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    Default Re: Repower options

    You can usually find a used diesel for not all that much money. Depending on the prop shaft size, you can probably use the existing shaft unless it is in poor condition. The prop can also likely be reused if you repower with a similar hp engine although you may have to repitch it. With a used diesel you can repower for say $4K-$5K depending on the engine cost. I went through this a few years ago with my 1936 32' powerboat. I went from a Chrysler Crown flathead 6 (~110 hp) to a 40 hp Volvo-Penta diesel. The new engine is quiet, fits under the cockpit sole and has all the power I need. I documented my engine decision at the link.

    I went with a new engine. My repower ended up costing about $12K, but that included a completely new fuel system from the tanks to the engine.

    http://www.todddunnmicroyachts.com/tortuga/repower.html


  7. #7
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    Default Re: Repower options

    Quote Originally Posted by Rattleandbang View Post
    Trim was a big concern which is why I posted the idea here. New diesel (and tranny and prop and propshaft) is out of the question because of cost, and I thought a I/O were all far higher displacement and power than a 50hp 4-banger?
    I also though about a well as there are tons of unused space belowdecks aft of the wheel, and I once had a sailboat with one for the outboard that worked ok, but that was just forward of the transom itself and only underwater in a chop or when heeling, and the thought of opening up the hull further forward with a big hole below the waterline seemed like an even more extreme violation of boat design. It's true that the volume aft of this boat is much reduced compared to forward, but a 50hp 4 stroke isn't that heavy and you'd think that could be balanced by ballast in the bow? I could get a good reliable quiet outboard for a fraction of the cost of any other kind of engine refit (and far simpler as well), which is why I'm scratching my head trying to figure out a way to make it work. If it's not realistic that's okay, but I want to make sure it's not an option before trying something else.
    Weight in the ends will increase pitching. Also uless an outboard has a trim adjustmant, it will cause the boat to trim bow up quite badly under power, particularly as you approach hull speed. So balancing an outboard with ballast in the bow will make pitching worse and is not a good idea for that reason.

  8. #8
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    Default Re: Repower options

    Quote Originally Posted by Todd D View Post
    You can usually find a used diesel for not all that much money. Depending on the prop shaft size, you can probably use the existing shaft unless it is in poor condition. The prop can also likely be reused if you repower with a similar hp engine although you may have to repitch it. With a used diesel you can repower for say $4K-$5K depending on the engine cost. I went through this a few years ago with my 1936 32' powerboat. I went from a Chrysler Crown flathead 6 (~110 hp) to a 40 hp Volvo-Penta diesel. The new engine is quiet, fits under the cockpit sole and has all the power I need. I documented my engine decision at the link.

    I went with a new engine. My repower ended up costing about $12K, but that included a completely new fuel system from the tanks to the engine.

    http://www.todddunnmicroyachts.com/tortuga/repower.html

    Great info, thanks. The problem with this approach is that while still remaining costly, it also still has a big chunk of engine in companionway and into the house. Maybe there really isn't a perfect solution.
    I tried posting pics to the thread, but it doesn't allow me to attach/upload pics; no matter how small I make them it wants them smaller until it's like a thumbnail.

  9. #9
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    Default Re: Repower options

    The engine I replaced extended through the bulkhead ahead of the engine in my picture and also about 8-10 inches above the sole. The new engine is 32" long to the transmission flange and 22.5" high. It weighs only about 400 lbs including fluids. The small size let me get it out of the cabin and under the sole with 2" of soundown insulation around the engine. I reused the existing prop shaft.

    Here is a picture of the old engine for reference


  10. #10
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    Default Re: Repower options

    Beta is where it's at. Diesels don't have to be noisy or smelly, and Betas aren't. But you want it to be cheap too? Sorry pal, that's not how the universe operates

  11. #11
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    Default Re: Repower options

    I repowered recently when the Perkins 4-236 in my boat committed suicide. We were able to find a pair of Volvo Pentas for a very good price and put one of them in place of the Perkins. (The other is a spare/parts cache.) My boat partner and I did all the work and so it was relatively cheap repower even including renting space at the yard and use of the yard's forklift. The new engine is lighter, smaller, and quieter. It also doesn't smell.
    Elect a clown expect a circus

  12. #12
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    Default Re: Repower options

    I can see how you got more space by chopping off 2 cylinders. Unfortunately, that's not an option as I'm already only sporting 4. I'd like to show the details with pictures but this thing keeps giving me an error saying files too big even when only 140k. how do I post pictures in this forum?

  13. #13
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    Default Re: Repower options

    Here we go. THis gives you an idea of how much the engine protrudes into the cabin.




    In this pic you can see how the engine space actually cuts the galley in half, not to mention making a lot of noise inside.





  14. #14
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    Default Re: Repower options

    Does anyone have experience with diesel engines from decommissioned lifeboats? We probably need to replace a 30 year old Volvo Penta model 2003 (28 hp, 3 cylinder) for our 33', 16000 lb displacement cutter. The same Volvo Penta 2003 engine is available, removed from lifeboats on ships, probably scrapped. The engines are reported to have been professionally maintained, run periodically, and sheltered somewhat from the salt air by being in enclosed lifeboats, but used very little. One question would be the extent of corrosion, despite the maintenance and shelter, over 25 or so years. There are minor modifications to the engines to meet SOLAS specifications. They come with transmission, wiring harness, and instrument panel.

    The obvious advantage is that with the same footprint and dimensions, it should be relatively simple to exchange the engines, using the same shaft and prop. We know the 28 hp engine worked well with the boat. A new Westerbeke 35E or Beta 30 will cost $9500 - $10,000, plus the labor of installation, which appears to be something of a roll of the dice. One of the lifeboat Volvo Penta 2003 engines, from a business in the UK, with shipping, will cost about $3300, with a minimal guarantee (90 days, you pay to ship it back). Installation should be much less - possibly something I could do with a crane and operator and some prof. guidance.

  15. #15
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    Default Re: Repower options

    Could somebody please state the factors and their relations that go to make up the calcs for working out screw pitch/gearbox ratio/engine revs/power?

    I'm in the same boat (so to speak) with a 33' cruiser sporting two Volvo Penta B18 units. They need a rebuild or we repower. The opportunity has come up to purchase two low hours B20 (AQ130) units instead, so I am wondering if I were to graft those to my existing boxes the prop pitch would remain suitable. The B18 and B20 blocks are essentially identical - they bored out the B18 from 1800cc to 2000cc to create the B20. The old engines were 83hp each, I believe, and the new ones 130hp. The attraction of course is that the grafting in work will be minimised. But I don't know how to work out whether the screw would need replacing, or whether the gearbox ratios would be wrong.

  16. #16
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    Default Re: Repower options

    Rattleandbang, I think you are being to hard on diesels with some very old fashioned beliefs based on oldtimers experience.
    Modern diesels are a very different engine to the smelly noisy engines you speak of.
    A Universal 4 put out about 50hp at 3000 rpm. Your installation has a very long gearbox which if you can shorten you will make more cabin room.
    What is the pitch and diameter of your prop? You should be looking for a replacement engine that will drive that prop efficiently.
    Which should be easy as most new diesels in this size range rev up to 3000 rpm and more.
    Speak to as many experts on inboard propulsion you can find and match the engine up.
    Most pleasure boats like yours run the prop at around 1100 rpm, so will require a reduction gearbox.
    Note this 53 mhp Yanmar offers 4 inline gearboxes for different setups;
    http://us.yanmar.com/media/ext/uploa...6cf2/4JH5E.pdf
    Other manufacturers should be able to give you a really good choice.
    Go diesel and you will not be disappointed.

  17. #17
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    Default Re: Repower options

    Aquinian, Most marine engines have their power/torque curves published somewhere. If you can find the graph of your current engine, and compare it with that of your proposed engine you will be able to see whether they are similar or not.

    A google search for 'propellor/power calculator' comes up with several hits.
    If you cant make it accurate, make it adjustable.

  18. #18
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    Default Re: Repower options

    OK, thanks Grant. I'm over-thinking this. All the talk about hull speed, efficiency, etc. She's a displacement hull that won't be doing more than a few miles each voyage (on the river) as a rule, so efficiency is not really an issue anyway. I'm told by the previous owner that hull speed is 10 knots (which seems high), but whatever it is I'll work out from experience where the revs that suit are and just putt along at those. Should be fine.

    Regards,
    John.

  19. #19
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    Default Re: Repower options

    Quote Originally Posted by Aquinian View Post
    Could somebody please state the factors and their relations that go to make up the calcs for working out screw pitch/gearbox ratio/engine revs/power?

    I'm in the same boat (so to speak) with a 33' cruiser sporting two Volvo Penta B18 units. They need a rebuild or we repower. The opportunity has come up to purchase two low hours B20 (AQ130) units instead, so I am wondering if I were to graft those to my existing boxes the prop pitch would remain suitable. The B18 and B20 blocks are essentially identical - they bored out the B18 from 1800cc to 2000cc to create the B20. The old engines were 83hp each, I believe, and the new ones 130hp. The attraction of course is that the grafting in work will be minimised. But I don't know how to work out whether the screw would need replacing, or whether the gearbox ratios would be wrong.
    I covered the relationships between the various factors in the link below. Given the horsepower increase you are going to have to take a lot of pitch out of your existing props unless you increase the gear ratio of your transmissions.

    http://www.todddunnmicroyachts.com/tortuga/repower.html

  20. #20
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    Default Re: Repower options

    My goodness, Todd, that is astonishing!

    You are a trojan!

    If you don't mind, am I right in suggesting that the only downside from the available power increase of 83 to 130hp per engine, without changing the props, would be increased fuel use? Mine's a displacement hull also. Because these are essentially the same engine blocks, the transplant would require next to nothing in terms of engine mounting/position changes, and really be just bolt out/bolt in, so the cost as a result will be say, sub-$5k all up, whereas any alternative will be $20k plus, and possibly a lot more. So you can see, fuel use is really a non-issue.

  21. #21
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    Default Re: Repower options

    Currently doing a couple of Beta repowerings. It really seems like a good choice if you're going with a new engine. They make an excellent product.

  22. #22
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    Default

    130hp seems high for the 2L engine... I had the carbuteted "high compression" version of that engine in a car and it was rated at 98hp. I'm inclined to think that if you dropped in the new blocks without changing a thing it would all work out just fine. You'll presumably end up slightly "under propped" so you won't be able to make use of the increased power (unless the new engines rev higher). This means you can't fully load up the engines, but that's not as much of an issue with gas as it is with diesels.

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