Neptune Outboard afraid of water

Home Forum Ask A Member Neptune Outboard afraid of water

Currently, there are 0 users and 1 guest visiting this topic.
Viewing 15 posts - 1 through 15 (of 22 total)
  • Buccaneer
    Buccaneer

    US Member - 1 Year
    Replies: 4068
    Topics: 980
    #1110

    Tried my 1936 OB34A 4hp Neptune twin the first time today after going
    through it. Had it on the outboard stand, and it started in three
    pulls, sounded great. I only let it run about 10 seconds, and killed it.
    Then promptly Baptized it in the test barrel with "not so Holy water".
    What I expected at this point was it starting with one pull, and pumping
    water like Old Faithful. I now have a blister on one hand, and a cramp
    in the other from pulling on it. The longest run in the test barrel was
    about three seconds 🙁
    It seem more promising after cutting back the high speed jet,
    and sometimes better when I retarded the mag from what I guessed
    was "start" position.
    The carb is a Tillotson MS-88A. Anyone know the initial high speed
    setting? I don’t remember seeing an adjustable low speed setting.
    It has a twist grip throttle. Should it start with the throttle closed,
    partially open, or?
    I have not checked the compression yet, but will do so before I tinker
    any more. Anyone know what’s acceptable compression on an old
    opposed twin like this?
    Thanks, Buccaneer

    Prepare to be boarded!

    Avatar
    b-morrison

    Canada Member - 1 Year
    Replies: 56
    Topics: 15
    #13347

    Try starting with the prop off. If the rings are stuck or worn, it may start and either loosen up/free the rings or….. I had an old evinrude where I did this..

    Tubs
    Tubs

    US Member - 1 Year
    Replies: 3148
    Topics: 172
    #13350

    Take off the prop and try again in your tank.
    If it starts and runs then your likely
    low on compression. Rings may be stuck
    (assuming you haven’t had the pistons out)
    and running it some and then letting it cool
    several times may start to free them up.
    Put the prop back on an see if there is any
    improvement. If there is continue to run it
    and use it till no more improvement can be
    achieved. If being stuck is truly the issue
    this will take some time before the gunk is
    all out and the rings are totally free so
    give it a chance. At that point you need to
    decide if how it runs is acceptable to you. If
    running it is not helping you need to consider
    other options. Good luck.

    You're only as smart as the person you're talking to.

    Avatar
    joecb

    US Member - 2 Years
    Replies: 402
    Topics: 61
    #13351

    It has an underwater exhaust tube , yes? Should be pressure relief holes in the Exhaust tube that are above the water level. Are these holes clear and open? or all plugged with carbon and "goop". back pressure on the Exh will make for difficult starting.

    Joe B

    RICHARD A. WHITE
    RICHARD A. WHITE

    US Member - 2 Years
    Replies: 1759
    Topics: 136
    #13354

    you can run it longer than 10 seconds, check cylinder temps with your hand, probably get 20 seconds or so. Use that time to get carb set. Mine also with MS88A carb. Do this a few times let it warm up then completely cool down, do it again, until it starts easy every time. As I recall I used about half choke to start and that helped alot…

    hope this helps

    Richard

    http://www.richardsoutboardtools.com
    classicomctools@gmail.com

    Buccaneer
    Buccaneer

    US Member - 1 Year
    Replies: 4068
    Topics: 980
    #13355

    Said Neptune was completely torn apart, de-carboned, cylinders lightly honed, new gaskets, etc.
    I did think about the back pressure on the exhaust tube. One of the tubes has a 3/8" hole
    high above the water line, but I think it’s the drive shaft tube. Not sure if the exhaust has
    a hole or not. It did not magically re-start after I took it out of the test barrel and put
    it back on the stand, but by that time I was pretty much tired of pulling, lol.
    My choke is spring loaded to stay open. It’s a chore to pull the rope with one hand,
    hold the choke closed with the other, and use the third hand to keep the lower unit from
    flipping up! Will check compression soon, but have to go eat Easter Bunny tomorrow.
    Happy Easter! Bucaneer

    Prepare to be boarded!

    Avatar
    mr-asa

    US Member - 2 Years
    Replies: 774
    Topics: 139
    #13356

    New rings as well? Maybe they need to bed in before it will run well?

    Avatar
    eltoquad

    US Member - 2 Years
    Replies: 206
    Topics: 49
    #13369

    I had the same problem with a twin Neptune and it was caused by loose main bushings. It’d start out of water but not in. I repaired them and it started fine there after. If it starts in water without prop on (motor will spin over faster) that’s probably your problem.

    Buccaneer
    Buccaneer

    US Member - 1 Year
    Replies: 4068
    Topics: 980
    #13371

    Eltoquad, The mains seemed pretty good for an 79 year old motor, but
    I did replace both bushings in the lower unit, which were shot for sure.
    I used some heavy camshaft installation lube on the mains when I
    put the crankcase back together, so it’s possible that it started on my
    first try, but not after the cam lube "thinned out".
    Did you have to line ream your new crankshaft bearings, or just
    install them?
    Hopefully will have time to play with it tomorrow!
    Thanks, Buccaneer

    Prepare to be boarded!

    Buccaneer
    Buccaneer

    US Member - 1 Year
    Replies: 4068
    Topics: 980
    #13389

    Had a little time this afternoon to work on the Neptune. Checked
    the compression, and both cylinders were at 60 psi. They’re the
    original rings, but maybe the compression would come up a little
    after the rings re-seat after the cylinder honing?
    Put a new condenser in it. Fired right up on the stand. Ran it
    about 30 seconds, tried tuning a little bit, but really not enough time.
    Put it in the test barrel, positively thinking it would fire right up
    this time….. WRONG again! Would hardly fire.
    Next time I’ll take the prop off and the exhaust tube and see
    if it runs in the water.

    Prepare to be boarded!

    Avatar
    dave-bernard

    US Member - 2 Years
    Replies: 1188
    Topics: 15
    #13397

    what is your oil mix maybe it needs more oil to seal things up. just thinking.

    Buccaneer
    Buccaneer

    US Member - 1 Year
    Replies: 4068
    Topics: 980
    #13404

    I believe the mix on this one was 2/3 pints to a gallon. I made a list in the garage of
    most of my outboards regarding what oil mix they each take…… amazing that
    so many of them were different! If all else fails, I’ll mix it extra rich. Thanks
    for the idea!

    Prepare to be boarded!

    Buccaneer
    Buccaneer

    US Member - 1 Year
    Replies: 4068
    Topics: 980
    #13413

    Thanks for the tips on worn out main bushings on the Neptune.
    You made a believer out of me. I got it running on the stand
    this morning for a few seconds. Killed it, removed the exhaust
    tube. Put it in the test barrel, and it wanted to run, but not quite.
    Put it on the stand, removed the prop, and test started it,
    and ran for a few seconds. Put the hyrophobic Neptune back
    in the test barrel and it actually started, but ran erratic, and
    for the most part, would only run with the throttle closed, and
    that was at a very fast idle…… but of course there was no
    prop on. It only ran for five minutes until it crapped in the
    barrel and died. Guess I’ll have to decide it I want to make
    it a runner or ornament. Wished I had measured crank bushings
    while it was apart 🙁
    How much would the 60 psi compression be contributing to
    the starting / running issue? I have no idea what’s normal for
    this engine.

    Prepare to be boarded!

    Avatar
    joecb

    US Member - 2 Years
    Replies: 402
    Topics: 61
    #13453

    60 psi is probably not to bad for that small motor. As for the bearings, poor crankcase compression will contribute to hard starting and poor idling. If you can detect side to side motion when rocking the flywheel then your bearing are sloppy.

    Joe B

    Buccaneer
    Buccaneer

    US Member - 1 Year
    Replies: 4068
    Topics: 980
    #13459

    Joe, thanks for the reply. If there’s any sideplay in the flywheel it’s
    minimal. I don’t think there’s room at add any seals with the
    crank bushings, but I’ll check it out if I tear it back apart.

    Prepare to be boarded!

Viewing 15 posts - 1 through 15 (of 22 total)
  • You must be logged in to reply to this topic.