Repower Inboard Prop Pocket Hull with Outboards?

Discussion in 'Boat Design' started by StandAlone, Feb 5, 2017.

  1. Barry
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    Barry Senior Member

    https://www.perfprotech.com/mercrui...-drop-in-motors-turn-key-engine/category/1602

    If your hardware on the engine is old and you want to upgrade, this site actually shows pricing of complete marine engine packages. Not sure exactly what 454 did for hp in 1988 but would guess maybe 360 ish? For $10,000 a pop, you can get 380 hp complete engines. Might need some instruments but maybe not. These are Merc engines according to the site

    Some interesting info
    Nada guides says your boat weighs about 16,400 pounds dry, add 4000 for fuel and water, and you have a 20,000 pound boat. Boat Test says about .7 statute miles per US gallon around 26 knots

    So if you bought say 2 new 350 hp Yamahas, 26,000 each, plus controls est 8,000,
    rework the transom and hang some brackets, 15,000 you are at $75,000.

    I would get someone to fill the prop pockets to ensure that you get on step. Maybe $15,000? add in some other incidentals and you are looking at an $80,000-$90,000 outboard repower compared to maybe $30,000 with a complete new Merc engine repower.
    The $60,000 difference pays for a lot of maintenance.

    Not sure whether twin 350 outboards would do the job. A lot of the new fishing boats in the 35 foot range are using triple outboards to get good performance
     
  2. StandAlone
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    Location: Melbourne, FL

    StandAlone Junior Member

    Excellent points everyone. Thank you to all who responded. After considering the responses I'm already leaning away from the Outboards.

    As a side note, the vessel has been surveyed in the last 6 months so structurally she's there.

    She was previously owned by a guy that owned a Glass company and is dry as a bone in the cabin. In 6 months of ownership we've seen numerous torrential downpours and a hurricane here in Florida and the cabin has not had water ingress that I can find during or right after the weather clears.

    The plan is to build this vessel from an entry level boat to one that we can use to cruise the inter coastal waters of Florida over the next 10-20 years.

    Thanks again!

    Ken
     
    Last edited: Feb 7, 2017
  3. Angélique
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    Angélique aka Angel (only by name)

    -
    Hi Ken, here's ‘‘Early Out’’ in 2010 she was repowered and now around the corner for sale...

    - 1987 Sea Ray 390 Express Cruiser
    - 2 x Marine Power 502 CID Chevy 420 HP - (426 hours, new in 2010 it says)
    - Direct Drives
    - 3 blade props
    - Port engine heat exchanger needs repair
    - asking: US $ 19,500.00


     
  4. Barry
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    Barry Senior Member


    Angelique, now your talking 840 hp, not drug running speed but moving up.
     
  5. Angélique
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    Angélique aka Angel (only by name)

    -
    ... Humm ... 840 HP ... moving up ...

    I'm a bit afraid a nowadays 3 x 250 HP outboard 40 knots Work Barge with a crane upfront and load of of buoys on deck and on the cabin top will pass this well loved puppy with ease . . ;)


     
  6. StandAlone
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    StandAlone Junior Member

    Angelique,

    I looked at that boat last year. It's a prime example of owner neglect. Aside from the overheating issues, there was water in the cabin when I saw it. I spent all of 2 minutes on board and could not wait to get out.

    If the engines are what they say buying it to strip for parts and power would be an idea but parking two boats on the hard would start to get expensive. Then what to do with the left over hull? It would cost $1000+ just to haul it to the landfill assuming they would take it.

    I'm going to head to the Miami boat show in two weeks and meet with repower folks and discuss options.

    Thanks again, Ken
     
  7. StandAlone
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    StandAlone Junior Member

    Quick question...

    The engines I have are 340hp and roughly 450 LB/FT of torque. If I were to consider a compact diesel engine package, would I be shopping for one with similar torque specs?

    My goal is to run 26 Kts top speed and cruise at around 17 Kts.

    Having two smaller inline diesels might be an option that allows me to at least get to the engines in the bilge. Currently with the V8's one must lay on top of the engine to do anything as clearance to the fuel tanks on both sides makes it too tight to access.
     
  8. Barry
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    Barry Senior Member

    No

    I can take a 10 hp engine run it through enough gears, ignoring friction losses, and create 450 pounds of torque.
    10 hp will not get your boat on step

    It takes a certain amount of sustained thrust to move your boat at say 20 knots. Thrust, force, pounds through a distance with respect to time is horsepower. ie work with respect to time, or the rate of doing work

    I would go to Boattest .com to see what diesel engines will give you the performance that you require, in a 1988 Searay Express.

    Price twin diesels, and controls and gauges, big ouch here.

    Consider the additional weight, new transmissions as the gear ratio will not be right, new props, not sure on the shaft diameters, probably require a return line for diesel to the tank though there is a chance that the 454's had a return line, will there be enough room for the new engines and transmissions, new mounts for both, the list goes on.

    I doubt that you will get a lot of additional space between the engines. Most of the intercoolers, pumps, impellors, water pump housing etc mount to the side of inline 4 or 6 and add to the width of the engine.

    Cummins has a reconditioned/reman program and I believe but not sure that a 5.9 without a transmission was maybe 30,000 US. Find the site, give them a call for a quote.

    Certainly, diesels offer better fuel economy but unless you are putting on thousands of hours, the fuel savings rarely come back to offset the initial costs.


    I would get a price on a repower from a reputable marine shop
    Diesels
    New Gas

    Say your boat is worth 25,000 in its current condition

    Gas Option 25,000 for your boat plus 20,000 for new 454's plus 7,000 for the install equals $52,000 ( if you had 454 at 340 hp, you might have had carbs, the new engines will be EFI and
    offer better fuel economy, not great but better

    Diesel Option Reman 25,000 for your boat, plus 60,000 for 350hp engines, 10,000 transmissions plus props, plus a tough installation equals 170,000

    Diesel Option New, even more, I could not find a site that had pricing of complete diesel engine packages with transmissions but assume it to be much more, may 30,000 more??

    If you sold your boat, and took the Reman option, ie spent 170,000 on a newer boat, with diesels, without the fuel inefficient tunnels, you could probably move up many years and get what you want
     
  9. StandAlone
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    StandAlone Junior Member

    Barry, All this truth hurts. :)

    Those are right in line with what I've expected as far as costs go. The logic is solid.

    If we didn't like the boat we wouldn't put the money in her. Heck as it is in just 6 Months I've got more in her than I'll ever get back, but hey it's paid for.

    I look at it this way, we've got a solid hull, love the layout and it serves our needs very well so to make it rock solid dependable I'd spend the money.

    That said, I know that every dime I put in her won't come back so even a gas repower will never pay back if I ever decide to sell.

    Ken
     
  10. Barry
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    Barry Senior Member

    Let us know which way you went and the costs as there have been many threads discussing the issue of repowers but unfortunately people are reluctant to reveal the actual final costs.
     
  11. StandAlone
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    StandAlone Junior Member

    Will do.

    I'm heading to Miami to hopefully tie-out with the right supplier. I will follow up here.
     
  12. Angélique
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    Location: Belgium ⇄ The Netherlands

    Angélique aka Angel (only by name)

  13. StandAlone
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    StandAlone Junior Member

    Looking like $14-18K each for a complete repower package with transmission is the starting point.

    This is the powertrain on a pallet. No labor, no fluids, no shop supplies no nothing....
     
  14. Mr Efficiency
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    Mr Efficiency Senior Member

    What is the pressing need to re-power ? I'm sure those old donks go through fuel at an alarming rate, but if still serviceable, you at least have something you can actually do basic maintenance on yourself.
     

  15. Barry
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    Barry Senior Member

    That seems a little high with respect to the link that I sent you. Mind you the transmissions add some to the mix.
    There are a lot of merc dealers out in your area. 14-18 sounds like top prices.

    Just one more thing, ensure that the exhaust manifolds are of the same type so you do not have to mess with re rerouting the exhaust hose. Ie most new engines are top center riser type, but some of the older ones had a lower discharge. Normally not a big issue to correct but something to be aware of
     
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