Melted piston!!!

1975 75hp Johnson, thought I had a blown head gasket or warped head... Took it apart, and found a heavily damaged middle piston, and the head is the same. Very deep pitting in both. The cylinder wall is not scored, and fairly smooth, only a little bit rough, but I believe that its just very minor surface rust from all the water getting in there.
Compression test in top and bottom pistons was the same, 138psi (cold). So now what do I do? Is it worth fixing? Can it be done by someone with limited experience? Or is this something that needs to go to a shop, or is it just not worth fixing? I have almost zero knowledge of 2 stroke motors, but they seem much simpler than a car engine, which I am fairly comfortable with fixing most things on. How much time and $ would this cost to repair?

Thanks for any advice, much appreciated!

Re: Melted piston!!!

Fixable? - Yes!
Price? - depend.
You will need an OEM workshop manual, no Seloc or similar!
You will need some 'special' tools like flywheel puller, torque wrenches and perhaps a hoist to get the powerhead/engine off. The rest is standard wrenches and sockets.

You will need at least one piston with rings and 2 ring sets for the other. A complete engine gasket kit and not to forget a new head. The one on the pics is not to be used again under any circumstances or you will be back to square one very shortly.

If you can do it, you have to decide, but it is not rocket science!

PS: Keep it off that shade tree mechanic that said it was just a warped head!!

Re: Melted piston!!!

Looks like part of the top ring let go. Before you jump into a rebuild, you should try to determine just what went wrong-first. Would be interesting to do an autopsy on the middle carb. Any chance that there is some dirt or debris inside the high speed jet that would restrict fuel flow to that cyl-causing it to run lean?

Re: Melted piston!!!

The middle cylinder of those 3 cyl engines has a bad habit of getting squeezed in an overheat situation. Impeller was recently changed, and I guess that was due to an overheat (http://forums.iboats.com/showthread.php?t=501898 , http://forums.iboats.com/showthread.php?t=505921
However if the overheat was from the piston seizing or failed cooling may be difficult to know.
But a check on carbs and ignition system is part of an overhaul.

Re: Melted piston!!!

Next problem! I can't seem to find the parts I'd need, on this site, or on the evinrude site either (says not available). Does that mean I'm SOL? Or can anyone tell me where to find a piston and cylinder head, and anything else I might need?
I'll add that a used 75-90hp motor (1980's) still goes for about $4000 from what I've found around here....
As for the mechanic, there are only 4 Evinrude/Johnson dealers in all of Alberta,Canada, (where I'm at) that I've found, and this guy is the only local option...
All help/advice is appreciated. I'm losing hope!

Re: Melted piston!!!

The only part I did not find was the cylinder head, but here:
http://cgi.ebay.com/ebaymotors/JOHN...at_Parts_Accessories_Gear&hash=item1c1dd35561

Other source except from this site:
http://www.marineengine.com/parts/j...rer=Evinrude&section=Cylinder+&+Crankcase

Never give up!
Alberta, Canada, a beautiful place, my sister lives in Edmonton, myself went skiing in Lake Louise a couple of times quite some years back (from Norway!), but no boating!

Re: Melted piston!!!

I did some quick googling and the .020 over piston sets are easy to come by for $90.
.030 no, but i didn't look too hard.
Find yourself a good looking head on ebay.

Re: Melted piston!!!

Watch out for piston quality on this engine. There are some low quality low-pressure castings out there at 'rip-off' prices. (WISECO I have used and knows that work, so does original).
They often ends up after a short times as:
R I P !!!

Re: Melted piston!!!

I can't seem to find the parts I'd need

Click to expand...

Std piston
http://www.marineengine.com/newparts/part_details.php?pnum=OMC0386311&ptype=&Engine=&Model
http://www.crowleymarine.com/parts/50416.cfm

Std ring set
http://www.boats.net/parts/detail/brp/B-0385807.html

.020 piston
http://www.crowleymarine.com/parts/50417.cfm
http://www.marineengine.com/parts/part_details.php?pnum=OMC0386314&ptype=&Engine=&Model

.020 ring set
http://www.marineengine.com/parts/part_details.php?pnum=OMC0385808&ptype=&Engine=&Model


.030 piston
http://www.marineengine.com/parts/part_details.php?pnum=OMC0386316&ptype=&Engine=&Model

.030 ring set
http://www.marineengine.com/newparts/part_details.php?pnum=OMC0385809&ptype=&Engine=&Model=

Powerhead gasket set
http://www.boats.net/parts/detail/brp/B-0385416.html

Head gasket
http://www.crowleymarine.com/parts/15987.cfm

Carb kit
http://www.boats.net/parts/detail/brp/B-0384412.html


Resources to scout additional parts that may be needed;
http://shop2.evinrude.com/Index.aspx?s1=02no5cf7g7bhevahsgqveesua4&catalog_id=0&siteid=1
http://www.google.com/

Google is your friend

Re: Melted piston!!!

Let us be a little nice ti IBoats for hosting this board as well:
http://www.iboats.com/Johnson-Outbo...7115489--**********.177725379--view_id.271408

Re: Melted piston!!!

I notice that your motor is a 1975 Johnson 75. Both Johnson & Evinrude offered a factory optional high-compression head for those very engines but dropped it soon after from non race engines. Perhaps you have a high-compression head and as such means the engine has higher octane fuel requirements. Sustained detonation from inadequate octane can crack pistons & break the ring lands. Just a thought.

Re: Melted piston!!!

All those "dings" are from ring pieces bouncing around in there. Stock standard pistons are out there, just takes some looking. I would hone that cylinder, then mic it, to see if you can get away with the stock piston before you order any. You may have to bore it out.
http://www.americanoutboard.com/ may have a used head. Start on ebay, that's where I found my head and piston. Good luck.

Forgot to mention, the hardest part of that job is cleaning the gasket surfaces, honest.

Re: Melted piston!!!

That head aint that bad, a machine shop can shave it about .020 and any remaining dings will fill in with carbon. Just make sure there are no ring pieces embedded to cause a "hot" spot. As to pistons I'll take a cast over a forged anyday. On that engine it has the "small" rods and most aftermarket piston need a rod kit to make work. (wrist pin size is different) I myself sell customers later model rods when I rebuild them as the rod kit needles are very small in diameter. Also thats a "stinger" block and could have the high compression head as posted earlier,below is my block I have for sale....
http://nashville.craigslist.org/boa/2672769366.html