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  1. #1
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    Need a little help with 1984 evinrude 90hp

    I have worked on mercurys for years. I don't know much about omc. I bought this motor to put on a pontoon. It had been sitting for years. Mice ate most of the wires and ants were living in water pump. I rebuilt carbs, fixed wiring and replaced water pump. Changing water pumps on these motors are a pain. I started motor on muffs. Tell tale was pissing strong, but motor felt like it was getting hot. I noticed a lot of water squirting out of various holes in front of lower and at lower mating surface. is this normal? should I drill and tap on top of block for the tell tale?

  2. #2
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    Yea, that is normal. You have an infrared temp gun? Thermostats maybe?

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  4. #3
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    that's good news!!!! I would rather dig a ditch all day than pull lower off again. there must be a special tool to get that linkage bolt back in. I struggled with it even with carbs off. No I don't have a temp gun. I pulled thermostat cover off. that's not easy either. probably a trick to that also. I removed every bolt in pan and it only gave me a little more room to work. Im gonna start it with therm cover off to make sure water is making it that far. Since mice and ants turned it into a condo, I was worried I had a clog somewhere. have a new kit with therms and springs/poppets to put in. I would like to have tell tale coming from top of block to always know im getting water up there

  5. #4
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    The gearcase can be fun. If the shift rod is bent, it can really be a pain. I use a 1/4" drive setup. A long extension, long enough to still have the ratchet on the outside of the pain, a impact swivel (the spring in it keeps it pointed right, or you can take a regular swivel and tape it up making it stiff) then I just put one wrap of tape to hold the bolt in the socket. Take a screw driver to hold the shift shaft into place from the other side. You get set up and it isn't so bad.

    I never added any holes. Unless there is a blockage somewhere it should bleed all the air out by itself. We used to use wax pencils to check the temp back then. Manual say it should melt a 123 degree pencil but not melt a 163 degree pencil. LOL!

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  7. #5
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    Mine would be too hot to touch and ran perfect for 30 years til I sold it
    Hydrostream dreamin

  8. #6
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    Oh yeah, those motors are no fun. Did you ever see the Tstats open up? those early ones had no access the Tstats, you have to pull the powerhead. AND, they give problems all the time. We probably have 4 or 5 of those 90 hp motors in the dirt that run perfect and have stuck thermostats. It just isn't worth the time messing with in my opinion. They burn loads of gas and have little to no resale value here; so why waste like $500 of your time pulling the lower and powerhead just to make it run cool again? There are no tricks to fix the Tstats aside from drilling access holes in the cowl like 3.0 optis have.

    Yeah and that shift rod going all the way up...like stated above its best to use a stiff flex 1/4" ratchet. I like the long springy screwdriver-like ones: https://www.amazon.com/Flexible-Shaf.../dp/B08C7VMTGZ

    Yeah they can be hot to the touch on the powerhead, but not melt wires and coils and such.

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  10. #7
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    I love mine. '79 100 that had new. Boat burned when it was 4 years old so I salvaged the motor and stored it. 15 years later when my son was old enough, I bought another boat, and put that old 100 on it. When through the carbs and water pump, never missed a beat. And I don't know where you are coming from as far as drinking gas. I always carried 18 gallons of gas and would ride and ski nearly all day and I would have at least 7 gallons left. It still has the original thermostats in it and has never had a head or powerhead off.

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  12. #8
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    Yeah its good when you don't have to do the Tstats. I mean they drink gas compared to I-6 mercs and 3 cyl Johnsons from the same era. I can run all day with my 80s 3cyl Johnson on 4 gallons. ALL DAY, sun-up to sundown. But, those were damn good engines that are hard to beat even with today's motors. I rigged a NIB 80s 88 special two years ago, it hasn't had any problems. Of course, I put a water pump in it before it went out, but yeah the tstats were original and worked good.

    In the original post he asked about water squirting out of the lower. I would guess it is normal without seeing a picture because it does dump water down the mid. But if you miss aligning the water tubes it will make a big fountain inside the mid and no water will get up. Are you SURE you hit the water tube(s)

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  14. #9
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    crossflows are a bit more thirsty but man are they tough and reliable. Plus they really scream! I ain’t never met a fishing in-line I couldn’t roast. I ran the hell out of mine and it never failed me. Had a couple issues over the years but only impacting performance not anything that needed the tow rope. Never had to change the water pump either. Dang good motors
    Hydrostream dreamin

  15. #10
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    Quote Originally Posted by 25two.stroke View Post
    In the original post he asked about water squirting out of the lower. I would guess it is normal without seeing a picture because it does dump water down the mid. But if you miss aligning the water tubes it will make a big fountain inside the mid and no water will get up. Are you SURE you hit the water tube(s)
    Yea, on the hose all the water dumps inside the can. When the boat is under way, at speed, the entire can will fill and water stream out of the idle relief holes.

    He said it had a good piss stream. If he missed the tube, I don't see that happening.

    BTW that old 100 is a high ring motor. I also have a very low time 79 140 and a built 2.6GT both with high rings. They'll live if you treat them right.

    And the fuel again... I was teaching my son how to ski and drive the boat. Plus when I had a competent friend, We would ski too. So we weren't just riding around.

    It'd run 48+ GPS with 18 gal gas, 450# of people, and a case of beer in an ice chest.. LOL I think it is a '74, tin boat, straight as a rail and no leaks.

    Click image for larger version. 

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    Sorry for the hijack Bullet123.

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  17. #11
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    Ran on the hose with therm cover off. Dumps plenty of warm water from block. Wow!!! I think changing thermostats is harder than putting lower back on. Its a good thing I still have all of my fingers. I had to use them all to hold the springs, therms, poppets, gaskets, bolts etc.. I think I even said a new cuss word. It feels cooler to the touch now. Appreciate the advice Crazy.

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  19. #12
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    Click image for larger version. 

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ID:	488965I paid $500 for it and would do it again. She is a freshwater cherry. Very little use. never had a wrench turned on it. impeller was original

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  21. #13
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    Quote Originally Posted by 25two.stroke View Post
    Oh yeah, those motors are no fun. Did you ever see the Tstats open up? those early ones had no access the Tstats, you have to pull the powerhead. AND, they give problems all the time. We probably have 4 or 5 of those 90 hp motors in the dirt that run perfect and have stuck thermostats. It just isn't worth the time messing with in my opinion. They burn loads of gas and have little to no resale value here; so why waste like $500 of your time pulling the lower and powerhead just to make it run cool again? There are no tricks to fix the Tstats aside from drilling access holes in the cowl like 3.0 optis have.

    Yeah and that shift rod going all the way up...like stated above its best to use a stiff flex 1/4" ratchet. I like the long springy screwdriver-like ones: https://www.amazon.com/Flexible-Shaf.../dp/B08C7VMTGZ

    Yeah they can be hot to the touch on the powerhead, but not melt wires and coils and such.
    you can do the stats by dropping the pan mounts, did it lots of times

    il6 150 Merc at WOT uses more fuel than a 140 for sure..
    Last edited by powerabout; 06-18-2021 at 05:52 AM.

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  23. #14
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    I did it with pan in place. It was a booger, but fixed now.

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  25. #15
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    Quote Originally Posted by bullet123 View Post
    I did it with pan in place. It was a booger, but fixed now.
    Shame they never shift the stats to the heads like a v6

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