Help..50hp johnson seized

[70'smotorguy]

I bought a 1973 johnson 50hp 2 stroke a few weeks ago.. This motor sounded great, very quiet for a 2 stroke motor.. I had it out on water twice. The first time it ran awesome, it was strong throughout the throttle and still quiet, no pings or knocks..
. The second time it ran great again.. Then.. It just locks up.. Felt the head and was barely warm, the fuel was 50.1 ... It didnt give a sign, a noise, nothing. I tried to start and starter wouldnt turn motor, took cowl off, felt that motor wasnt hot, and was able to turn flywheel by hand, but was pretty hard... Tried to start again... It started, motor still quiet, but wasnt running as strong.. Shut it off and now its seized up.. I can move flywheel about 1/2 inch, both pistons moved a little(enough to know they not seized).

What happened to this motor?
Any guesses?

Thanks guys

 

[flyingscott]

Take the lower unit off and see if the flywheel turns then.

 

[70'smotorguy]

Yeah, I just got to thinking about that... I really believe it is the lower end, as I move the flywheel back and forth that 1/2 inch I hear a clank in the lower unit...
. What couldve seized up in there? Almost feel like a bad spline in knuckle gear. If so, what couldve cause this?
Oil was just changed

 

[racerone]

Who changed the oil ?-----Was it filled from the bottom till oil came out the vent ?----What type of oil ?

 

[oldboat1]

Is there oil in the lower unit or was it dry?

 

[Tim Frank]

Who changed the oil ?-----Was it filled from the bottom till oil came out the vent ?----What type of oil ?

^^^^ ?

 

[Lightwin 3]

If it is a "73", those were Powershift II, as I recall.

They required a specific lube. OMC/BRP Hi Vis as I recall.

 

[70'smotorguy]

Its a 73, but I dont see anything about powershift on it.... I put lucas lower end oil in it.
same lower end oil I run in my 76 evinrude

 

[70'smotorguy]

And yes, oil was full, but not overfull

 

[Fed]

The last time I had a clank (70HP) some of the piston pin rollers decided to leave the motor, the only way out was via the combustion chambers where they got slammed by the pistons. I could only move the flywheel back & forwards a few inches.

 

[racerone]

" powershift II " is not electric shift.----It refers to the fact that your lower unit uses oil pressure to assist the shift motion to make it seem effortless.

 

[F_R]

If it is a 1973 50hp with electric start, it is Powershift. Manual shift models were not Powershift, but I've never even seen a Manual Start 50, since the old 1959 V-4s

 

[Lightwin 3]

" powershift II " is not electric shift.----It refers to the fact that your lower unit uses oil pressure to assist the shift motion to make it seem effortless.

You're right, it's not. 73 was the first year after the electric shift.

I had a "73" 85 that We ran for years. We waited for the model year change due to advice from a dealer freind of ours.

 

[70'smotorguy]

Ok, so im confused... This 73 50hp operates just like my 76 70hp evinrude... I do not understand the shifting you talking about.. 1 foward gear 1 reverse gear... Did the lucas lower unit oil destroy it?

The only clank I get is from lower unitwhen I attempt to move flywheel, sounds as if a gear is bound up... Ill take it off this weekend to see

 

[racerone]

Well most motors have forward / neutral / reverse.-------There are different ways to move the clutch dog.----Hence different description / names for lower units !!

 

[oldboat1]

Lucas oil is fine (marine synthetic). Assume the noise and binding went away when the l.u. was removed and the flywheel rotated(?)

 

[Bosunsmate]

Have a look through the sparkplug holes if you want a quick assessment

 

[70'smotorguy]

I took off the lower unit and motor is fine... Lower unit locked up tight... Actually see a spot on the casing around where the water impeller is that is dented outward... I havent taken it apart to examine what actually failed... Anyone wanna take guesses before I pull it apart?

Ill post what I find maybe tomorrow or sunday.

 

[Bosunsmate]

Upper LU bearing has failed and come up into waterpump housing, putting driveshaft off centre and chopping up your lower gears is my guess.
Flush your motor out by putting a hose on medium pressure in the inlet tube, all sorts of bits and things may be up there now

 

[5150abf]

You blew a gear in the lower sounds like, chunks of gear are getting in the teeth and preventing it from turning.

The way a lower works, there are 3 gears and a clutch dog, the 3 gears are always meshed and turning if the engine is running,

When you shift the clutch dog moves forward or back on the prop shaft and engages the gear.

Been through a couple lowers and that is what it does, almost always in deep water at full throttle so you unfortunately need a new lower.

New gearsets can be had on ebay for @$250 but you need to be carefull how you assemble it, clearances are tight.