1983 Evinrude 15 HP

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  • Rusted Junk

    US Member - 1 Year
    Replies: 38
    Topics: 10
    #238323

    Hi All,
    I sold a few of my old Johnson motors and in lack of better judgment I took this 15 HP Evinrude as partial trade. The Evinrude has a cooling issue, I replaced the complete impeller, housing, base plate , seals ect. Still the same issue, very little water flow. I removed the thermostat housing and the old thermostat and found the opening behind the thermostat partly clogged, so I cleaned that and blew compressed air thru the complete motor, it appears to flow air thru the complete cooling system. We’ll see . My question is there was a spring inside the thermostat housing between the housing and the thermostat , has anyone seen this type of set up before?? None of the parts diagrams show this spring but it appears to be holding the thermostat against the head. I am not sure whether this is the correct thermostat or not, temperature of 143 stamped into it. , I cleaned it up and put it in hot water and it opened. Just not sure about that spring, any help would be appreciated.
    Thanks,
    RJ

    910B31AF-6300-4D66-937A-C14F10309947

    0BEE2BE1-1AB0-4614-A759-41813F8F1547

    • This topic was modified 1 month ago by Rusted Junk.
    • This topic was modified 1 month ago by Mumbles.
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    billw

    US Member - 2 Years
    Replies: 1483
    Topics: 45
    #238331

    The spring is there because it allows the thermostat to lift off its seat at higher speeds, for additional cooling. 143 degrees is correct. 15s are great motors with one big problem: Over time, the upper water tube grommet under the power head gets pushed in by corrosion and blocks a great deal of water flow, which will lead to overheating. It is an odd situation because often, you can’t tell this is happening by just looking at the tell tale output. If it were my engine I would spend the time, pull the power head and clean this area up, replacing the grommet. You’ll also need the power head base gasket. Have a propane or Mapp gas torch ready. You may need it on the inner exhaust housing/tuner bolts. Then again, you might not, if you’re lucky.

    Long live American manufacturing!

    1 user thanked author for this post.

    Fred Hickman


    Replies: 12
    Topics: 7
    #238332

    Rusted Junk: billw is 100% correct. Your issue is the UPPER WATER TUBE GROMMET !! Follow his advice, then your overheating issue will be HISTORY. I had an identical problem with a 9.9 last season.

    1 user thanked author for this post.

    fleetwin

    US Member - 2 Years
    Replies: 3829
    Topics: 39
    #238333

    Like Bill says, chances are good that you have a grommet issue, especially if this engine has seen salt water use. Adding insult to injury, this 15hp may have two pesky grommets. Later model 15hps like yours have an “open inner exhaust tube”, along with a short water tube exiting the powerhead….
    That being said, I am assuming that you cleared out the overboard indicator hose and plastic restrictor nipple, oftentimes these are plugged…Surely don’t want you to pull this thing all apart needlessly.
    And yes, like Bill says, that spring belongs there, allowing the thermostat to lift off its seat at higher RPMs, so more water flows through the powerhead, bypassing the thermostat. Be sure to order the new rubber seal, and be sure the SS cap is in place over the new seal. Carefully clean out the thermostat pocket so the thermostat won’t be stuck and can move freely off its seat, once water pressure can overcome the spring pressure.
    In spite of some unforgiveable issues, these are great engines. The powerhead and gearcase are very robust. The cheesy plastic throttle gears are a pain, and the cooling system needs regular maintenance when used in salt water. Be sure that little water drain in the bottom of the gearcase is thoroughly cleaned out while you have the gearcase off, you may want to enlarge that drain hole a little bit as well…

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    Rusted Junk

    US Member - 1 Year
    Replies: 38
    Topics: 10
    #238355

    Thank you all,
    I did find the parts diagram and see the spring,retainer, gasket and thermostat, I have these .ordered. I am a where of the grommet issue and may have to pull the power head to fix that, but I’ll put the thermostat in and see if I get lucky , the passage to the upper over flow hole is clear, if I blow compressed air thru it I can feel and hear the air coming out the water pickup on the lower unit, so we’ll see. Next is the issue with the the throttle gears in the handle with broken cogs , the plastic gears inside the cowling don’t seam to be broken but I am sure they are worn.looks like those parts aren’t cheap. This is the little motor that keeps on giving I guess.
    Thanks again for the advise.
    RJ


    rudderless


    Replies: 138
    Topics: 5
    #238397

    Your 1983 has the head with the thermos at the bottom unless one has put on a later year head. The early heads ran 143F all the time. Maybe that’s the confusion with the thermos and your manual. Later years used the head with the thermos on top that lifts off during higher water pressures.

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    fleetwin

    US Member - 2 Years
    Replies: 3829
    Topics: 39
    #238441

    Well, I hope you do get lucky and don’t have to attack the grommets…Didn’t mean to jump the gun, guess I have seen too many of these. I remember the first one I discovered back in 1981. Just want to make sure I understand your post…The engine didn’t pump well before you replaced the water pump, correct? Any possibility that the water tube is misaligned and not going into the impeller housing grommet correctly? Perhaps someone bent up the water tube on a previous attempt. Perhaps the intake screen is plugged up with debris from your test tank. This engine “looks” fairly clean, has it been used in salt water? The gear housing castings are very thin under the forward part of the SS impeller plate, and erode badly….This might be causing the pump to suck air instead of water…Don’t get this confused with the other scalloped cut out under the impeller housing that is supposed to be there…
    You can be fooled by using compressed air to blow through the water tube…The compressed air usually has enough pressure to “open up” the grommet allowing air through it, whereas the water pump doesn’t develop that much water pressure….Keep in mind that this 15hp probably uses the two water tube set up I mentioned in my earlier post, so if the outlet grommet was collapsed, you would still feel air coming out the telltale hose blowing through the intake water tube.
    Again, I want to be wrong, so feel free to ask plenty of questions and provide any more info that might help us help you…I surely don’t want you to pull the thing apart needlessly….The grommet job isn’t too bad on fresh water engines, but salty ones usually require the torch…Sometimes trying to pry that powerhead off the exhaust housing can be a challenge also, be careful not to break the motor pan with pry bars.
    There is a way to install the new grommets “improperly” that will avoid this issue in the future, hopefully we won’t get that far and it will pump fine with the new thermostat….Don

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    outbdnut2

    US Member - 2 Years
    Replies: 1533
    Topics: 80
    #238446

    Are you using an OMC impeller? The 15s and 9.9s are the only motors I ‘ve worked on where Sierra impellers, even with a new Sierra housing, do not pump at slow trolling idle. On three late 1980s motors I found this and the OMC impeller fixed it.
    Dave

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    fleetwin

    US Member - 2 Years
    Replies: 3829
    Topics: 39
    #238456

    Are you using an OMC impeller? The 15s and 9.9s are the only motors I ‘ve worked on where Sierra impellers, even with a new Sierra housing, do not pump at slow trolling idle. On three late 1980s motors I found this and the OMC impeller fixed it.
    Dave

    Good point indeed!

    1 user thanked author for this post.

    Rusted Junk

    US Member - 1 Year
    Replies: 38
    Topics: 10
    #238467

    The impeller is a Sierra I believe, the motor pumped some water before I changed the impeller but not enough to cool it correctly. I would say the motor has been used in salt water, this is the PNW we are surrounded by salt water,,but not sure to what extent, the water pick up tube is in the impeller housing correctly and I ran a wire up into it and didn’t see any corrosion come out but that doesn’t mean there is not a blockage there.I am waiting for the thermostat seal, retainer and housing gasket to arrive then I’ll test it again. I still have to address the broken throttle gears in the tiller handle too. Lucky I have very little investment in this motor, My goal was to service it and make sure it ran nice and sell it.
    Rusted Junk


    fleetwin

    US Member - 2 Years
    Replies: 3829
    Topics: 39
    #238469

    Was it overheating before you got it? Is the head/block discolored/burned paint? You won’t see any corrosion coming out of the water tube when probed that way, it is the actual smushed rubber of the water tube that may be blocking water flow.
    OK, so the water pump parts are Sierra, you may want to invest in an OEM water pump kit just to rule out that possibility. We will see what happens when you replace the thermostat. Remove the overboard indicator plastic pan restrictor fitting just in case there is crud in there blocking the hose. Again, be sure the water tube isn’t bent and is fitting correctly into the impeller housing grommet.
    Post some pictures of the powerhead so we can see if overheating was an issue before you got this engine.

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    Rusted Junk

    US Member - 1 Year
    Replies: 38
    Topics: 10
    #238482

    Yes this is the way I got the motor, I sold a 57 FDL11 to a fellow that was going to put twin 18 hp motors on an old boat he bought , I took the 83 Evinrude and a mint condition 54 Johnson QD14 as partial trade. If you look real close at the thermostat cover you can see the paint may have gotten hot, but nothing on the head or block that I can see. I will have my infrared thermometer to use to check motor temperature this time when I run it. The problem my very well be blockage of the rubber grommets. My goal is to get it running perfect and dependable and sell the motor to someone that needs a 15 HP short shaft.
    The motor is in the shop at my lake home , I’ll be heading there when the outboard and some gun parts I have ordered show up.
    RJ


    fleetwin

    US Member - 2 Years
    Replies: 3829
    Topics: 39
    #238526

    OK, so no real big evidence of overheating before you got it… Did it overheat as soon as you ran it the first time? Or, did you judge cooling by the lack of telltale spray? Again, those telltales do get plugged up. It is best to remove the plastic nipple, then blow back through the hose while the engine is running. Once the hose is clear, let it run with the plastic nipple for a few minutes to clear any other crud that might get stuck in there, then reinstall the nipple. The fact that the engine doesn’t show much signs of overheating prior to you getting it kinda suggests the grommets might be OK…The usual scenario is that these engines get overheated, then folks try everything to fix the problem except the grommets…The engine continues to overheat, then the owner gets rid of the engine….But, usually there are obvious signs of overheating, burned paint, melted wiring….
    I know we have focused on the flaws of these engines, but don’t misunderstand. The powerheads and gearcase are really very rugged, and they are great little engines for the most part. A 15hp short shaft model is pretty valuable these days, so don’t “give it away”….Who knows, you may want to keep it…

    • This reply was modified 3 weeks, 6 days ago by fleetwin. Reason: correction

    Rusted Junk

    US Member - 1 Year
    Replies: 38
    Topics: 10
    #239839

    Update on the 83 Evinrude 15HP, I installed the thermostat, spring and retainer with a new gasket, ran the motor with the lower unit water muffs on it and the motor had a strong water stream form the tell tale Port, used a digital thermometer to test head and block temp, got constant readings of 137 to 145 degrees after 20 minutes of running at various throttle settings, so happy with those results. Now on to replacing the the throttle shaft / gear and the ball gear which are both missing a few cogs.


    fleetwin

    US Member - 2 Years
    Replies: 3829
    Topics: 39
    #239852

    Cool!

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