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Old 02 September 2014, 11:44   #1
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Problem: Johnson 1999 15hp

Hi

I recently purchase a 1999 Johnson 2 stoke 15hp engine. Engine looked good inside and under the cover - nice and clean.

Over the weekend I took it out to a place with a 5mph speed restriction where my dad keeps his speed/power boat. The idea being to cruise up and down @ 5mph for a while to test the engine.

After 15mins, the engine just stopped. I kept a close eye on the engine to make sure it was pumping water and it was. I was actually looking at it when it locked up.

  • Engine started fine on second pull
  • Water was pumping out the back nice and strong
  • Fuel appeared to be flowing fine, certainly no blockages in the pipes
  • Petrol was mixed perfectly - (I do this all the time on a 75hp 2 stoke)
  • I didn't give it any beans. 5 - 6mph according to GPS (Boat was not planing)
  • It's not a gear box problem
So I take the pull cord off and remove spark plugs. I ensure the engine is in neutral. I am unable to turn the flywheel, it is totally locked.


I look down the spark plug whole and I can see what looks like a piston ring sticking out from the side of the piston.


What could cause an engine to lockup doing 5 - 6mph?


James
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Old 02 September 2014, 14:26   #2
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You mean other than a broken piston ring?
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Old 02 September 2014, 14:32   #3
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Quote:
Originally Posted by ShinyShoe View Post
You mean other than a broken piston ring?
Yeh, What would cause the piston ring to break at 5mph.

I can rule out overheating and non-mixed fuel.

I have a feeling the engine has been stripped and rebuilt.

Thanks

James
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Old 02 September 2014, 14:39   #4
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Strip it and see. Your view at the moment isn't going to tell you much apart from what you've already said.
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Old 02 September 2014, 14:56   #5
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Ring already broken but in place... Then moved..

Previous lack of oil or over heat?

Bore not quite cylindrical?
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Old 03 September 2014, 12:22   #6
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It looks pretty simple to take the powerhead out, so this is what I am going to do. I may open the power head myself or send it to an expert who does this all the time to diagnose and find out the cause of the issue.

There is no point fixing it until I can find the root of the problem.

The main worry is if the head, crank, or rods are screwed since these are the real expensive bits and will determine if I've wasted a lot of money or not.
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Old 06 September 2014, 15:16   #7
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I am still in the process of stripping this down.
I took the head off it and the piston along with the cron rod just pulled straight out.

OMC, Johnson & Evinrude - CRANKSHAFT & PISTON - 1999 Johnson/Evinrude 9.9

On the diagram, it looks like the screws (part 7) snapped, and then killed parts 6 and 9. The bearing pins look like they have no wear on them at all. It all looks fresh, so I am wondering if it's been rebuilt and maybe not run in or a crap rebuild job just to flog the engine.
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