Need help getting my old motor fired up.

Discussion in 'Outboard Maintenance' started by firecat1981, Jul 12, 2009.

  1. firecat1981

    firecat1981 BBA Counselor

    I have an old 1970 18hp evinrude and I'm having trouble getting her fired up. The motor sat on my garage floor after I bought it for 2 years but now I want to use it for a skiff I'm building.
    I changed out the plugs and cleaned the carb, but can't get her to crank up. I've never dealt with a motor this big so I don't know how easy it should be to pull the cord. It feels kinda stiff, maybe its just the size of the motor. anyway if I choke it all the way after a few pulls I'll get a big pop or backfire, but thats it.
    any advise? I need to figure out if this motor will work quickly or else I'll have to delay my project.
  2. rkmurphy

    rkmurphy Well-Known Member

    I just got done ripping apart my '98 Merc 25. Took everything apart except the actual block...didn't wanna mess with internals...

    They are relatively simple motors and with a shop manual, it should be even easier.

    In my opinion...I never heard good things about the 70s Evinrudes. But I do remember hearing somewhere (probably here) that some year range of the 18 hp's were may be the one you have. I would pull the head cover off and inspect the cylinders...if scored I'd forget it on a motor that old. If it looks good, rub some 2 stroke oil on the walls and put the head cover back on. I forgot to mention...when you take it off, try not to damage the gasket. Try to get it running before you start investing in new gaskets.

    Now start looking electrical...check wires, stator, etc. Not sure how to do that...that's why I took Brett's advice about getting a shop manual ;D.

    Also check the reeds to see if they look good. Make sure the carb is tuned right. I can't think of anything else right now...but it should be a fun project. I hope you get it running! It definitely is rewarding...check my outboard maintenance thread out...I'm a first timer. It was a pain in the ass but it works better than it did when I got it back from the mechanic.

  3. Brett

    Brett > PRO STAFF <

    It's an old motor, but they all have the same requirements to run.

    Air, fuel, lubrication, spark, compression.

    With 2 strokes the compression is in 2 places.
    Inside the cylinder and inside the crankcase.
    If the crankcase isn't tight and the reeds aren't seating, no fuel will get to the cylinders.
    If the fuel system isn't tight from tank to intake manifold, again no fuel to cylinders.
    Check all lines, filters, primer ball and fuel pump.
    If the pistons are worn out and the cylinder compressions aren't good, same problem.
    No spark means no ignition of the fuel air mix.
    The carb is old and hasn't been rebuilt, rebuild it.
    Check the timing.

    As rk said, get the shop manual.
  4. noeettica

    noeettica Well-Known Member

    all the above Plus ...

    I always look for a full bowl of fuel

    and an open main jet

    look for good blue spark

    look for at least 100 psi compression

    If you have all that give her a little shot of either to get It's attention ....
  5. firecat1981

    firecat1981 BBA Counselor

    thanks for the reply guys!

    So I was out there messing with her again, I checked for good spark and both cylinders fired ok, I knew the carb was in good shape because I just took it apart and it was totally clean inside. I knew it was getting gas cause I squeezed a little to hard and few drops leaked out the front of the carb. so now what.......well another friend told me not to mix up the wires when I switched the plugs, so I was very careful to put them back as I found them. I yanked on it for a while then checked everything again, well one wire had a metal tab on it and it said up. only thing is it was on the lower cylinder, DOH! ::).
    The previous owner had them backwards when he sold it to me :mad:. well I switch them around, choke her up again and after 3 pulls I get signs of life, I back the choke off, give her a pull and......Bruuumuuugh....Brum Brum Brum Brum.......

    She ran strong and very smooth!!! WooHoo ;D

    Now in the 15-20 seconds I let her run I frantically looked for a pee hole to see if it was pumping, hmmm no luck. Where does this motor expell its water? it wasn't coming out of the exaust like my 4hp, where's it go? :-/
  6. Brett

    Brett > PRO STAFF <


    If your motor looks like this the exhaust and water come out near the cav plate, not through the prop.
  7. rkmurphy

    rkmurphy Well-Known Member

    Good news! Get that thing purring like new then repaint it and re-badge it. You'll have a nice classic that's light as can be.
  8. firecat1981

    firecat1981 BBA Counselor

    My motor does look like that, except its a long shaft, but I have parts on the way from a friend to switch it to a shorty tiller. is the exhaust hole the one right under the cav plate? is so is the intake the 3 holes to the side? and if so whats the other hole half way up the motor that looks like an exhaust?

    I'll repaint it eventually(spray can job) and I'll put new stickers on it, but I was thinking about a play on the new E-techs. I'd use the same lettering but have it say NO-TECH ;D
  9. Brett

    Brett > PRO STAFF <

    fixed it for ya.... [smiley=happy.gif]

    exhaust is bottom rear of cav plate so as not to interfere with prop
    halfway up is the backpressure relief hole
  10. firecat1981

    firecat1981 BBA Counselor

    thanks brett, I'll be putting in a new impeller before I crank it again, is there anything else I should do besides change the lower unit fluid?
  11. Brett

    Brett > PRO STAFF <



    Replace the seal(s) on the screws for the lower unit drain(s)
  12. Un-shore

    Un-shore Well-Known Member

    I'm guessing here but did you have it running with ear muffs when you could not find the pee hole?

    My 4hp Mariner will not pump water hooked up to muffs, I have to put it in a bucket. I have no idea why, maybe because the lower unit is so small most of the water sprays off to the sides.

    After you change the impeller and if still no stream try a bucket. Make sure the water level is up past the water pump.
  13. Un-shore

    Un-shore Well-Known Member

    depends on what you find when you change the fluid and impeller. Look for water in the fluid and metal chunks on the magnetic drain screw. Check the boot on the shift rod for cracks or tears. If your old impeller is missing pieces you will have to check for clogged cooling system.

    Like Brett said, replace the screw gaskets with brand new ones whether the old ones look good or not and screw them in tight. Use a screw driver with the flat part as wide and thick as the slot in the screw to keep from damaging it.

    Replace the drive shaft o-ring and put water proof grease on the shaft splines.

    You might know all this already, if so excuse my rambling. :)
  14. firecat1981

    firecat1981 BBA Counselor

    I had the motor sitting in a big garbage can while it was running, because of the way it is situated you can't really use muffs. when running the exhaust is under water so you can't see if its peeing or not.
    Thanks for all the advise on what to do, I'll be working on her again soon enough.