Please help me identify this boat

Discussion in 'Powerboats' started by Jnmjude, Aug 7, 2018.

  1. Jnmjude
    Joined: Aug 2018
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    Jnmjude Junior Member

    Ok. It looks like a friend from home can help me out with an old mercury 85hp thunderbolt thats not being used for the time being. Ok so its not 150hp, but miles better than the 50, and at no cost (unless i wreck it!) That gives me space to sell the 50 and save up for something with more grunt.
    Will the 85 also struggle to the same extent or is this a sensible idea?
    Thanks
     
  2. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    You will still be operating on the fringes, but you may get it to plane out in flat water.

    The thing you are not understanding here is these boats are designed for rough seas. They are heavy. And anything too small will leave you bow high.

    Give the 85 a try. You will probably need to reprop it. Probably the motor will be propped for a lighter boat which means it probably will be wrong for yours. You will know this if the engine can't get to full throttle. Too small a prop and the engine will wind out, overrev etc. If the engine can't achieve wot, then you won't plane out either. So, expect to reprop. When you get to the water someday; you don't want to think the 85 is too weak, but it will probably be overpropped and unable to achieve open throttle and unable to plane. All guesses here, but probably good ones.
     
  3. Mr Efficiency
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    Mr Efficiency Senior Member

    I thought 85hp Mercury would be almost extinct, but as Fallguy says, it will need to be propped down to be able to rev freely. An old thing like that might be down on power, too, compared to its earlier days, even if a good goer, it won't want the boat too heavily loaded to get on plane. The thing that might help, is trim tabs, that lowers the get on/stay on plane speed, If you'd have said 85 hp Johnson/Evinrude of the same vintage, I'd say it would work, they certainly had more guts than the 85hp 4 cylinder Mercury.
     
  4. Jnmjude
    Joined: Aug 2018
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    Jnmjude Junior Member

    Thanks guys, so really its a no again, just to be safer.
    I get the principles just fine, i know its a heavy boat, and boats need power to get on the plane, and less power to stay there where they are at their most efficient.
    What i am trying to compromise on is the fact i have bought, somewhat fallen for and committed to restore a boat that needs a beast to be efficient, and i already own a 50 which is not suitable and have been offered the use of an 85 to give extra power. The engine is almost as old as myself so reduced power is very possible. If there is literally no point entertaining anything under a 100/110 and pref much more then i just have to wait and save up in order to take the boat for a spin.
    Your advice is greatly appreciated. Ive not a huge amount of experience with different boats, and you can only learn from solud advice and experience.
    Thank you
     
  5. Mr Efficiency
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    Mr Efficiency Senior Member

    What sort of engine is the 50 you have ?
     
  6. Jnmjude
    Joined: Aug 2018
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    Jnmjude Junior Member

    Its a 92 evinrude 2 stroke.
     
  7. fallguy
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    fallguy Senior Member

    Cross the engine bridge when you get the boat fixed up, but consider prepping for a bracket; especially if you need to repair transom or stringers.

    You have a lot of work to do before you even put an engine on it if there are major repairs.

    I sold a non running 100hp motor for 100 bucks.

    If you are near the coasts; motors are always in tougher shape. Look inland for better condition engines for a budget. You have time.
     
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  8. Mr Efficiency
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    Mr Efficiency Senior Member

    Two of those would do the job, and give you a cruise speed of 20 knots. Not fast, but enough. And as a bonus, the security of knowing an engine failure won't leave you needing assistance at sea.
     
  9. Jnmjude
    Joined: Aug 2018
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    Jnmjude Junior Member

    I think Fallguy has the right idea. I dont need an engine whilst i have no stringers and deck. Il sell the 50 and put the money in a pot, topping it up each month with what i can. I may be able to find a more suitable engine over winter when boating stuff tends to be cheaper.
    I could look for another 50 to twin it with but id rather have one lump on the back im happy with. Lets face it, a single 100 will weigh less than 2x50s, so probably do a better job. Though it would be nice to have a failsafe, the area il be using the boat is very busy (the solent and just in the channel) theres a good breakdown service out here that will normally get to you within an hr that costs approx 100 quid membership a year (seastart), loads of other boats for help etc. If i lost power, as long as i wasnt in imminent danger, it wont be a massive problem, just a massive pain!
     
  10. fallguy
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    fallguy Senior Member

    Twin 50s would be better for redundancy. If one konks out and you are 10 miles out to sea; return on one engine.
     
  11. Jnmjude
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    Jnmjude Junior Member

    Dont twins have to be the same engine though to keep things balanced? Could i put an earlier and later 'rude 50 together or would it have to be another 92?
     
  12. fallguy
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    fallguy Senior Member

    Aesthetics would be the only reason. The rotation of the engines doesn't matter really here either.

    You set up separate batteries and even separate tanks if you want and then the fuel systems are also separate.

    Then the boat has redundancy. If you want only a single engine; you really need to get into the 2000 and newer four strokes and a used 2000 will be a 20 year old engine then, so 2010 is a better cutoff.

    I am not saying you can't put a vintage engine on it; just that ocean runs are not as safe with a 30 year old single engine.

    Mr E's idea is not a bad entry level idea. You might end up wanting more like two 100s someday; so build accordingly.
     
  13. Jnmjude
    Joined: Aug 2018
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    Jnmjude Junior Member

    Hmm. Its a thought! Ive never thought of having twins, but then a 150hp on an 18ft boat seemed like overkill when we first started talking so maybe not.
    Ive got even more scope then if im not limited to have to have the same make and model for each. I presume i have to find a twin throttle control box for them though and fabricate some kind of steering arm to connect them both. Not the hardest thing to do though. Cheers.
     
  14. Jnmjude
    Joined: Aug 2018
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    Jnmjude Junior Member

    I am correct i thinkig you have to have the same horsepower for each engine though arent i.
    Would the difference in power/torque be negligable if i used a 50 rude and a 50 yamaha/mercury etc?
    I dont know much at all about twin set ups. I always thought they had to be exactly the same and one had to counter the others rotation. My learning curvenis going to be steep i think!
     

  15. Mr Efficiency
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    Mr Efficiency Senior Member

    You would need the same make, a Johnson or Evinrude, with that 2 cylinder engine block, they came in various HP ratings over the years, from 48 to 60. There would still be a few out there.
    A lot were sold, but getting old now, of course. They are all right-hand rotation, and that doesn't matter too much. Neither would differences in nominal HP, I once replaced a 90 hp with an 85hp Johnson on a twin set-up, and it still felt the same, although the replacement motor had slightly less cubic capacity. The boat ran the same as before. And I swapped over the 90 hp cowl from the dead motor. No difference to be noticed !
     
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