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1972 Seastar 15 foot/50 HP Johnson

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  • 1972 Seastar 15 foot/50 HP Johnson

    I recently bought a 1972 Seastar with a 1972 50 HP Johnson. Engine runs well and I've learned a LOT from all of you in the last few months. Of course, a little knowledge is a dangerous thing--now I just have a lot more questions! --First off--how much should the bare boat weigh? The data plate says 1795 fully loaded, allowing for six people (150 pounds each?), motor (200 lbs?), etc. Would the boat itself then weigh around 7-800 lbs? How to check this?--Next, it seems that the hull is two pieces (upper and lower) and I'm wondering if there is foam (maybe soaked foam?) in between. How to check without destroying the hull?--Finally, how fast should it go? I'm getting 25 mph with two people; the motor seems to be running strongly, but I don't (yet) have a tach so I don't know if I'm propped correctly, if the hull is water-logged, or if that's all I'm going to get with 50 HP... --One more--how fast do you have to go to pull a skier? Don't imagine I have enough ponies for that, eh?Thanks in advance, Rich


  • #2
    Re: 1972 Seastar 15 foot/50 HP Johnson

    hey knot2 much, check out the reply to your post on sept 4. I'd really like to hear from you and share some info on these old seastar boats! thanks a bunch, Rocks

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    • #3
      Re: 1972 Seastar 15 foot/50 HP Johnson

      Guess there aren't too many Seastars out there--hoping someone has a similar tri-hull with a 50HP Johnson...anyone have any ideas on speed/weight/construction with regard to my prior posting above? Thanks again, Rich

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      • #4
        Re: 1972 Seastar 15 foot/50 HP Johnson

        25 mph seems fine for your boat, motor and load. I had a Homelite 55 4 stroke (55 horse), and the best I got was 22 mph on my 17 ft hull. I now know it has a low cylinder, so I will rebuild it, but the 85 horse Merc I replaced it with has me up to 31 mph. You would have some difficulty with skiing, 50 horse just isn't enough, unless its kids you are pulling, or the skier is skilled enough to adapt to the lower power. You could be able to know if it has excessively soaked foam by looking at how low it sits in the water with no one on board. I have seen soaked foam boats in the water, and they sit several inches lower in the water, and are difficult to get on plane. You could also just open the floor in a few spots and check. If it is soaked, you have the fine honor of seperating the upper hull from the lower hull (they are usually bolted together behind the rubrail) and either drying or replacing the foam. Yeah, the empty hull probably weighs in the 700 lb range.
        Project Skanky Beast http://70silverline.250free.com/Skankybeast.html

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        • #5
          Re: 1972 Seastar 15 foot/50 HP Johnson

          Thanks--how do I examine the flooring? What's under the carpet--fibreglas or wood? I'm trying not to just tear the carpeting up--do I have any other options? If I leave the boat outside or in the (unheated)garage over the (Chicago) winter and there is water in the foam will it split the hull? Thanks again, Rich

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          • #6
            Re: 1972 Seastar 15 foot/50 HP Johnson

            You could do the icepick test on the floor, but that won't tell you if you have saturated foam (if you even have foam at all). If it is saturated, it probably has been for quite awhile, and previous winters would have damaged something, I would think. I kind of think you are fine, just based on the speed you are getting. Does it get up to plane and speed fairly quickly, or does it seem to take an eternity? In the end, the only way I can think of to be sure is to pull the carpet and examine the floor. You would probably have to cut a few small holes to check. Good luck...
            Project Skanky Beast http://70silverline.250free.com/Skankybeast.html

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            • #7
              Re: 1972 Seastar 15 foot/50 HP Johnson

              Jason--Thanks for your replies. It gets up on plane pretty well I guess--this is my first boat so I don't have much to compare it to...First couple times out the motor ran a bit rough and sputtered quite a bit but it had been sitting for 2 years+ (remnants of old gas in carbs) but the more I run it the smoother it runs. It's still not as smooth/crisp as I think it should be during acceleration--I'm starting to wonder about the reeds. Can I open the throttle plates and look down her "throat" with a flashlight or must I pull the carbs in order to get a good look? I'm familiar with 2-stroke motorcycle engines and reed valves so I understand the theory; it's just that the parts are situated a bit differently. Hey by the way I really appreciated your earlier post on building your own rectifier--stopped by radio shack today and bought a bridge rectifier and as soon as I find a chunk of aluminium I'm there. Next QQ--what about the shifting diode? How can I cheat OMC/Bombardier out of $79 and build my own one of those? Thanks again, Rich

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              • #8
                Re: 1972 Seastar 15 foot/50 HP Johnson

                The reeds are probably fine. The fact that it has sat for two years leads me to believe that the carb could use a good cleaning. Gas builds varnish and gunks up pretty quick if left in the bowls that long. I have seen bowls almost solid with jellied gas, not pretty. You could pick up a rebuilt kit (kits) and tear 'em down, clean 'em up, and I bet it will feel like a new motor. Also make sure there isn't old skanky gas in the gas tank. The water pump should be replaced as well, its cheap and easy, and you'll thank yourself, I promise. If you havn't already, you should change the spark plugs as well, they are cheap and can make a world of difference. Can't help you on the shifter diode though, sorry.
                Project Skanky Beast http://70silverline.250free.com/Skankybeast.html

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                • #9
                  Re: 1972 Seastar 15 foot/50 HP Johnson

                  Just thought I'd pop in on the Seastar thread, I picked up a 15' tri-hull just a few weeks ago.

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