LU failure..

[Zeltron]

Hello all!! I’m in a pickle... just got done restoring my 1964 14’ fiberglass Smoker Craft and I put a 1993 Johnson 50hp on the back. I COMPLETELY rebuilt the LU, new gears, bearings, seals, the works. Filled it with premium marine gear lube. The old prop was in sad shape... (17”x11 3/4 pitch) got a new Solas replacement (17”x 12 pitch) anyways, I made sure all everything was in order... took it on a fishing trip. It gave me two GREAT days. On the third day, it all went to crap. I was cruising along and all of a sudden lost all power and I’m dead in the water. Literally 7 hours on the motor. Well prop won’t spin when in gear... I get her home and when I pull the plug I find the worst thing a boat owner could find. The plug is full of shavings and the oil is BURNT, BLACK, and “Frothy”. What on earth could cause this??? It was brand new. I haven’t had the courage to take the whole thing apart yet but I don’t understand how the LU could get that hot and burn the oil after 7 hours... please and opinion would be welcome.

 

[jakedaawg]

Heat comes from resistance. Did you set it up yourself? Did you use the special tools and a factory manual? Factory gear set? Did you have the case checked before assembly? There are just so many ways you can mess up a gear case while setting up its gonna be hard for someone to say over the nets. One thing is certain, you can't just replace bearings and gears without re-shimming.

 

[racerone]

How did you shim the gears ?----How did you fill the lower unit ?---How much oil did it take to fill the lower unit ?

 

[Crosbyman]

I am no expert in props but a 17 x 12inch dia prop on a 50hp ?? that seems like a pretty big egg beater prop

maybe that caused the LU engine to strain

 

[racerone]

Model # is required.----Is this a 2 or 3 cylinder motor !----Commercial model ?

 

[Crosbyman]

OK THAT IS A 12 X 17 NOT A 17 X 12 BUT AGAIN AT 17INCH OF PITCH IT JUST SEEMS LIKE MUCH

 

[Faztbullet]

My bet is failure to check shimming...anytime you change gears,driveshaft or a bearing shimming has to be checked....

 

[Zeltron]

UPDATE: To answer the questions, yes I did shim it. I am a hands on learner and this is my first rebuild but I had supervision while doing it. The model number is J50TLETB. After i got the courage (a few beers) i took the LU apart and found that the lower half of the pinion was completely chewed away. I removed the driveshaft and found that the top bearing had failed causing the driveshaft to slip up in the housing. this $10 bearing destroyed the gears... I am still at a loss as to how the unit overheated. i know for a fact that it was COMPLETELY full with lube.... but alas... it could have been much worse. a bearing a couple thrust washers and a gear set... expensive but better than trying to find a new motor..

 

[Zeltron]

OK THAT IS A 12 X 17 NOT A 17 X 12 BUT AGAIN AT 17INCH OF PITCH IT JUST SEEMS LIKE MUCH

it is a 12 pitch 17" diameter.

 

[Faztbullet]

It overheated when gear failed...the metal gets reallll hot.