Rebuild my outboard? Whats necessary? My 50HP failed

merc20076

Petty Officer 2nd Class
Joined
Sep 9, 2009
Messages
156
This year is not at all a good season for problems with boats and outboards. 3 weeks ago, I got a good 16' fishing boat with low hours on it. But when I went test it for a good hour + the 5-6 first times, it ran like new. But last Friday, major problems started on my way back. Was cruisin' to about 25 MPH when suddenly the motor stopped. It started right back up and got on plane ok but after another 30 sec, It did it again. Now when I wanted to try to restart it, something seemed to force, and it did restart but it ran really rough and didn't keep an idle. SO I shut it off and came back with my 4.5HP kicker.

When I got back home I did a compression test and the motor was still warm and the readings were from top to the bottom 120-80-120. Then I opened up the head cover and I can see that the middle cylinder wall is scratched, so I presume a broken ring? And what caused that, me I blame the oil injection. I've checked the water pump and it was ok but anyways it did pee well and the water coming out was warm.

Now, used 50HP are rare to find. I am planning to get a factory service manuel and getting the parts to rebuild it myself. Is just getting oversize pistons and rigns+ all powerhead gaskets is enough or I absolutely need to get new bearrings, crankshaft seals?

And if I want to do it myself, I will delete oil injection and mix gas-oil 50/1 in the gas tank, where is the oil injection location?

Thanks for helping me!

BTW: The outboard is a Johnson 50HP 1997 J50TLEUR
 

retiredfornow

Petty Officer 1st Class
Joined
May 9, 2011
Messages
355
Re: Rebuild my outboard? Whats necessary? My 50HP failed

Same thing happened to my 60. First, get a factory manual, one place is ebay. It'll guide you thru removing the powerhead. You'll be able to stand on the boat and lift it off once loose. You'll have to split the cases in order to remove the middle cylinder rod cap. Pull that piston out and you'll probably find that the rings are stuck tight to the piston. There's your loss of compression, the rings aren't working. When your motor stopped, it was due to seizing. That's when the piston welds itself to the cyl. wall.
You may be able to hone the cylinder in place to try and remove the scratches on the cyl. wall. Once that is done, you'll need to mic the cylinder to see if it's in spec. Refer to specs in your manual. If it is, you may be able to put in another piston of the same size. Keep everything spotless!!!!! That's one economical way to go. When you hone, do it in a way that the mess drains down out the top of the cyl. But first, order a manual, you'll need it. Good luck, and try to figure out why it seized in the first place.

Piston = $75 to $100 plus or minus
Head gasket = $20 plus or minus
Manual = $35 plus or minus
 

txheat

Recruit
Joined
Jun 29, 2011
Messages
3
Re: Rebuild my outboard? Whats necessary? My 50HP failed

Don't forget to change your thermostats too. A customer lost a 150 earlier this season to a failed t-stat...almost the exact same scenario you described as well. Hope you get it back on the water soon!
 
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