1978 Johnson Seahorse 70HP Qestions?

Discussion in 'Outboards' started by Traxxasmaxx, Jun 9, 2010.

  1. Traxxasmaxx
    Joined: Jun 2010
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    Location: Florida Gulf Coast

    Traxxasmaxx 1978 Johnson Seahorse

    I am new to boats and some help would be great. I put my motor in a tub of water and I don't see any stream of water running out anywhere? There is a black rubber hose plug off but I honestly dont know why water would come from it because the hose comes from the left side of the motor. Does anyone know where this stream would come from on this outboard?
    Just under the engine cover on the back of the motor is two parralel holes could that be it?
    And if I need a water pump where can I find one.
    I want to take this boat out bad but it runs mint so I just dont want to hurt the motor.
    Any help or tips period about anything or everything is much apprietiated.
    Thanks ~Will~
     

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  2. powerabout
    Joined: Nov 2007
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    powerabout Senior Member

    The exhaust cover ( the large flat plate)on the left side is where the tell tale hose comes from on one of those.
    It should be a small plastic elbow just above the lower cowl towards the aft angled down and aft in the photo.
    It comes out on the stb side of the lower cowl.
    It could be blocked with sand or dried salt anywhere from the plastic elbow ot the outlet fitting.
    The thermostat is 143 degrees so you can put your hand on any part of the powerhead when running.
    Water will only come out of the 2 exhaust relief holes at the back after the thermostat opens and or the water pressure opens the pressure relief valves.
     

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  3. capt littlelegs
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    capt littlelegs New Member

    I used to work on outboards back in the 1980's, my memory isn't that good but I'll give it a try. Before you take it out I would strongly suggest you give at least the bottom end a good service and check over to avoid breaking down and possibly overheating the engine.

    Start by draining the gearbox oil, it may be white where water has gotten past the seals, unless the seals are replaced, not always that easy, you will need to change the oil often. To refill you can get EP 80/90 oil in tubes to fill from the bottom, then refit the top screw then the bottom one.

    Remove the gearbox from the leg applying heat to any stubborn bolt threads but don't snap them off, they are fragile. Put the gear into reverse and disconnect the gear linkage probably just above the gearbox. remove the water pump cover and check the pump condition for signs of running dry. If the impellor is broken up you need to remove the bits from inside the water pipe to prevent a blockage. Check this is clear by putting hose water through it. Fit a new impellor and grease it and other moving parts and bolts with water pump grease. Turn the shaft to make sure the pump is free. Refit making sure everything fits properly especially the water pipe in the pump and the gears work as they should, may need adjusting so remember how many turns on the linkage.

    The two holes are probably the exhaust relief ports and there should be some water coming out, some outboards have no tell tale but normally it will be to one side near the top. There maybe a screw above the oil vent screw for a hose adaptor otherwise a water muff is used to supply water if a tank is not available. You should be able to get parts from any OMC dealer, I may have a manual if you need detailed info.

    I don't know what the rubber hose is but a picture would help.
     
  4. Traxxasmaxx
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    Traxxasmaxx 1978 Johnson Seahorse

    Couple of crappy pics from the phone.

    Ok these pictures are junk but in the one pictures you can see the black hose coming out and it is pluged off.
    The other picture is on the left side of the motor and you can see where the that same hose is hooked up.
    Thanks for all the info guys it helps alot.
     

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  5. Traxxasmaxx
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    Traxxasmaxx 1978 Johnson Seahorse

    powerabout thanks for all the info. It gives me a prety good idea of how the cooling system works. I just need to figure out where all the parts are located. And in that picture you posted I see the same hose on the side or your block that mine has.Its to the right and you can barley see it. Is it some kind of breather or something? I am used to snowmobile, dirtbikes and cars. The entire boat design is completly new.
    Capt LittleLegs. Thanks for all the help. I am a little nervous about taking the lower unit off now to replace the water pump because I dont want any bolts to break. I have a friend that works at the marina so I am thinking I might drop it off for a pump? I just hate spending the money cause I normally do my own work on things. I also notice a stamp on the boat says max 60HP. I have a 70HP on so do I have to worrie? I am not going to be using it as a speed boat and everything seems solid
     
  6. Traxxasmaxx
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    Traxxasmaxx 1978 Johnson Seahorse

    more pics

    pics of the 1966 Wellcraft
     

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  7. capt littlelegs
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    capt littlelegs New Member

    I still can't see the hose but the tell tale outlet comes off that flat plate that contains the cooling water over the exhausts in powerabout's picture, Follow it to the outlet and check it is clear throughout. Probably just as well to get someone to do it first time, you'll know everything is freed off for next time. The gearshift is disconnected under the carbs I believe. Siezed bolts are more of a problem in salt water, keep them greased and plenty of WD40 all over everything.

    70hp on a 60hp transom is obviously going to strain it a bit plus the extra weight but hopefully it is strong enough to not exceed any margin allowed, just don't hammer it and find a hole where the outboard should be!!
     
  8. marshmat
    Joined: Apr 2005
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    marshmat Senior Member

    These power ratings are calculated based on the boat's hull type, internal volume, beam and control configuration. It's assumed that the builder will provide a structure capable of handling anything the largest allowed motor can toss at it. With a boat of this age, it's worth checking to make sure none of that structure has rotted or deteriorated.

    If the boat is structurally sound, I wouldn't worry too much about your over-limit motor (at this age, it's not putting out 70 hp anyway). On most trailer-dwelling boats, the stresses on the motor mount from bouncing along a gravel road are larger than those from the actual propeller thrust- hence the bracing bars that you see connecting the trailer frame to the outboard on many boats.
     
  9. Traxxasmaxx
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    Traxxasmaxx 1978 Johnson Seahorse

    ok so it turns out that rubber hose that looked like it was plugged of was actually where the water sprays out. I took the hose off for kicks and sprayed it out with a air hose and some water and sure enought it was full of salt. Thanks guys!
    The transom looks solid all around and the boat has brand new floors. I am trying to figure out what paint is best for this old dog. Every forum I read is different. I just want something hard and durable. I don't care if it is shiny or not. Just strong and clean looking. Any opinions on EasyPoxy Brushable paint?
    Any ideas on wiring a boat would help to. Does this motor charge the battery? Or do I need a charger to keep it charged?
     
  10. powerabout
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    powerabout Senior Member

    The motor charges
    Alternator is 6 amps non regulated
    Dont use a sealed battery with this system
     
  11. capt littlelegs
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    capt littlelegs New Member

    What do you need to wire? Presume you've got the standard wiring and controls for start stop? Once running you may need to check that the charging coil and rectifier are working with an ammeter or test lamp. There is ample current for keeping the battery charged and a few navigation aids but don't expect a lot more. You will need to use a battery charger on occassion and before leaving it to prevent permanent damage especially if using more power than the engine produces.

    It probably doesn't matter what gloss paint system you use so long as you prepare it well to prevent it peeling off.
     
  12. Traxxasmaxx
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    Traxxasmaxx 1978 Johnson Seahorse

    Power!

    I planed on hooking up the lights to some switches. Three lights total. One for the floor, bow and stern. Was thinking about a cheap marine radio? I could just run it off a seperate back up battery and charge it after use. Its not a show boat but here in Tampa Bay it is nice having a little beater. Once I get the seats, paint and tunes going this thing will be all I need from a boat.
     
  13. capt littlelegs
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    capt littlelegs New Member

    That should be ok and also to run the radio, put your battery in a proper secured box and run a suitably sized pair of cables to your switch panel. Fit a main auxillary fuse and a main battery isolating switch away from the box to avoid sparks igniting any battery gas.
     
  14. Traxxasmaxx
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    Traxxasmaxx 1978 Johnson Seahorse

    igniting any kind of gas......very bad.Thanks for the tip Captain
     

  15. dustycrockett
    Joined: Jun 2010
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    Location: Texas

    dustycrockett Junior Member

    traxxas, the telltale hose outlet is a nipple on the lower cowl, starboard side.

    You can access online schematic diagrams and parts catalogues at http://shop.evinrude.com click on "electronic parts catalogues", select "johnson" in the dropdown box and drill down to your hp/year/model#

    Water pump service seems intimidating at first but you can do it:
    1. remove prop
    2. to disconnect the shift linkage remove the 7/16" hex head screw under the bottom carb accessible from the port side of the engine. I find it's easier to get to if I remove the front of the fuel pump and move it aside. It's held in place with a thumbscrew. There's a screen filter there you need to inspect anyway.
    3. remove the trim tab (scribe a mark across the edge so you can get it back like it was).
    4. remove the retaining bolt up in the trim tab cavity.
    5. remove the other retaining bolt from the bottom side of the antiventilation plate.
    6. remove the four retaining bolts from the perimeter, just above the antiventilation plate.
    7. pull the lower unit off.

    the shift rod height is adjusted by screwing it in or out, so don't twist it or else it won't fit when you put it back.

    8. There's a grommet around the driveshaft, don't forget it.
    9. Four hex-head screws hold the water pump housing down.
    10. Slide the old impeller off the drive shaft.
    11. Slide the new one on. Slip the woodruff key in place just before the impeller covers the keyway.
    12. Put a new housing gasket in place.
    13. Grease the inside of the housing (trailer axle grease is fine), and shove it down onto the impeller while turning the driveshaft clockwise with your hand. Don't use any kind of tool on the driveshaft splines.
    14. Fasten the housing back on.

    On reassembly:
    * put molly lube on the drive shaft splines (but not on top, there's not enough clearance).
    * the rubber o-ring just below the drive shaft splines -- you need that.
    * put omc gasket sealant (or some kind of anti-sieze) on the retaining bolts -- or else corrosion will set in & it'll be a ***** next time.
    * use 3m #847 or permatex #2 on the joint between midsection & lower unit. www.ishopmarine.com has 847 -- permatex is way harder to clean off there next time around.

    I find it's easier to get it back together if I disconnect the shift lever from the cable (starboard side of the powerhead). Just pull the small cotter pin.

    Your motor will run best on Champion QL77JC4 spark plugs gapped at .030.
    Use only fresh 87 octane gasoline mixed 50:1 with TCW3 certified oil. I add 1 oz. of Seafoam per gallon -- BRP Engine Tuner, Yamaha Ring-Free, or similar. Highly recommended.
    Use a "Marine" lower unit gear lube if you can get your hands on it...it will tolerate water a little better than automotive without breaking down.
     
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