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Old Mariner/Yamaha 8A Waterpump or Thermostat?

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  • Old Mariner/Yamaha 8A Waterpump or Thermostat?

    Hi all,

    I just picked up an old Mariner 8hp 647-L 6773 which was made in Japan by Yamaha in 1971/1972 --- she looks great for 40!

    However she is not pumping water and it turns out parts are really hard to find. I can find an impeller 655-44352-09 online but can't locate any water pump kit other than the one for the 1972-1977 later 8A's -- any thoughts on if the later ones might work?

    Bigger issue is that the thermostat 655-12411-81 is "obsolete" and I can't find one anywhere... How much difference is there between thermostats? There is one for the 8B's from the early 80's 677-12411 but none of the older ones anywhere!!!

    I am in Australia but as long as the companies will ship to me I can buy online.

    Is it possible to test the existing thermostat and maybe reuse it? Alternatively just how much difference is there in thermostats? The all look the same to me LOL!

    cheers and thanks

  • #2
    That year model motor was not sold here in US as an Mariner or a Yamaha motor and we don't have any parts catalogs on it. Not sure if any other parts would work in it. The thermostat can be tested in pot of water heated up, thermostat should open at about 140-160 degrees
    Regards
    Boats.net
    Yamaha Outboard Parts

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    • #3
      On my 1999 Yamaha I replaced my thermostat recently for the first time since new, just as routine preventive maintenance. The old thermostat was working fine and after cleaning with some mild acid and an old toothbrush, keeping it for a spare....that said, your thermostat may well be just fine, clean it and test in some hot water, pop it back in there!...Good Luck!

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      • #4
        Thanks Robert

        I will try that and let you know how I go!

        Cheers

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        • #5
          No Thermostat!

          Originally posted by robert graham View Post
          On my 1999 Yamaha I replaced my thermostat recently for the first time since new, just as routine preventive maintenance. The old thermostat was working fine and after cleaning with some mild acid and an old toothbrush, keeping it for a spare....that said, your thermostat may well be just fine, clean it and test in some hot water, pop it back in there!...Good Luck!
          Thanks Robert,

          well I pulled the cover off the thermostat and low and behold NO THERMOSTAT! I do live in the tropics so cold weather running is never an issue but do you think I should try and get one to put it in?

          Also I scrubbed and scraped at the area under the thermostat and down the back of the cylinders (a vertical water tube of some sort) and when I fired her up again I managed to get water out the pee hole!

          thanks

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          • #6
            stat needs to be in place to help force water to all parts of motor as designed. other wise you will end up with hot and cold spots.

            If nothing else find a washer to install to act as a restriction

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            • #7
              I'm just guessing here, but if you can find a thermostat that's the right diameter/size to fit in the spot where it goes, and it's made for a water-cooled outboard motor, maybe buy it, put it in there and give it a run! Could be from another brand or HP motor...might work!

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              • #8
                8hp mariner - yamaha japanese version 8A-647

                well I have read a few folks who cant locate anything for these 647 motors including me. I searched all over and finally found that marineengine.com you can find diagrams under Mariner 8A Outboard Motor Parts by Serial Number Range

                just click on 655-000300 & Below

                most of these part numbers should work. So I easily located an impeller and a lot of the other parts are obsolete including the thermostat. I found a NOS one on ebay for $45 crazy! I was working on it with my bro and said you know I have a few spare OMC #378065 or #5005440 or Sierra #18-3543 thermostats with rubber gaskets for a V4 90hp. Magic they are an exact fit same temp too. popped it in and perfect. The ones I got were for a 1985 Evinrude 90HP VRO V4. Here is a link to the thermostats I got on ebay. Wulffe Marine.

                2 Pack Thermostat Kit with Gasket for Johnson Evinrude 5-235 Hp 434841 5005440 | eBay

                I had to get on here and post this after the hassle of getting a thermostat. Hope it helps.

                One thing hard to find is the recoil plastic gear. Marine Engine has it but its $52 with ship. Might have to grit my teeth and buy it

                Comment


                • #9
                  5 years later, ????

                  Anyway, congrates on finding the parts.

                  Re salt build up, you may want to try a Rydlyme treatment to get the rest of the salt out.

                  A couple of links of interesting reads:

                  http://www.yamahaoutboardparts.com/f...g-th19434.html


                  http://www.yamahaoutboardparts.com/f...m-th23666.html


                  http://www.yamahaoutboardparts.com/f...h27868-p2.html
                  Scott
                  1997 Angler 204 CC, 2006 F150 TXR

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