Merc 200 Connecting Rod (no longer does)

[WaltCorwin]

After mere 6 month restoration effort, EndorFin looks beautiful. And ran perfect too, for about 6 hours. Following a thrashing and grinding, I pulled the head to find #4 connecting rod in a thousand pieces. No hole in the piston, or any sign yet of serious scoring on cyl walls or crankshaft. I've replaced every screw, fitting, and wire on this boat (except for the motor), so I am going to try and rebuild it myself. No outboard experience.<br /><br />1984 Merc 200 V6. My question is, and I welcome all comments, what might have caused this, and what do I need to be extra careful of to prevent a re-occurrance?<br /><br />The previous owner said the motor had been rebuilt approx 200 hrs (running time) before he sold it to me. I believe him. The boat had been sitting on a trailer for approx 3 years before I bought it and dragged it home. <br /><br />In the middle of the hull restoration, I got bored and decided to try and start the motor. Turned over but wouldn't run. Couple of shots of starting fluid (since found out that was a really dumb-ass move) and it fired right up (and ran away FULL THROTTLE for about 10 seconds before I was able to shut it down). After sleeping for three years, that was probably quite a wake-up call for the old motor. <br /><br />Have since drained fuel tank, replaced all fuel lines, rebuilt all three carbs, and replaced all cooling system (hoses, thermostats, poppit valve, etc). That's all I've done to the motor, and like it said, it ran perfectly for several hours.<br /><br />So, getting ready to spend several days/nights and probably SEVERAL hundred bucks on this repair, and your moral support might help ease the pain.<br /><br />Walt Corwin<br />DeBary FL<br />'82 Chris Craft Scorpion 213 Center Console

 

[Chinewalker]

Re: Merc 200 Connecting Rod (no longer does)

Hi Walt,<br /> Hate to be the bearer of bad news, but I think you may have killed it three years ago when you fired it off with the starting fluid. Starter fluid is BAD NEWS in a 2-stroke outboard motor. It literally rinses all lubrication from the internal surfaces, bearings, etc. Unless you pickled your motor afterwards with fogging oil, it is likely is sat the last three years with no oil protecting the internals surfaces, particularly anything steel, from rusting or corroding. It may have built up some surface rust - not enough to lock it up, but enough to make things a little rough when it was restarted this year. A few hours running time and those rough spots take their toll and things get to rattling and eventually something lets go.<br /> Understand, this is my theory, as I can't take a look at the crank journals and bearings in your motor to see for sure. Motor disassembly may give you a better idea...<br />- Scott

 

[WaltCorwin]

Re: Merc 200 Connecting Rod (no longer does)

Thanks very much for the reply Scott. Just to clarify, I used the starting fluid AFTER it had been sitting for years. Hope that lessened the impact. I'll let ya'll know my progress.

 

[sparkroost]

Re: Merc 200 Connecting Rod (no longer does)

When you over-rev, especially with no load, you stress the con-rod. It also doesn't help it have been sitting for years. The water collects in the lower bearing and rusts the balls. Once this happens you have to replace the bearing. The pitting caused by rust will cause vibration which will cause failure. You will be lucky if your crank is good now. Big $$ item. If the con-rod went, then the piston probally hit the head. I am afraid you are in for some costly repairs. Cylinder scoring is not a big deal since you can re-bore. Plan on new pistons, crank, bearings.. the whole 9 yards. Might be better to find a good worn out powerhead and re-build. This way you have good main components. I would guestimate you will spend minumum 1200.00 if you do it yourself.

 

[Bradster941]

Re: Merc 200 Connecting Rod (no longer does)

In your 1st paragraph you said it ran 6 hours, then took a dump. When you pulled the head, did you do it carefully and examine the head gasket? <br />I wonder if maybe the head gasket failed and you sucked water into that cylinder. Did you see in the cylinder any signs of rusting or white crystals?<br /><br />As far as rebuilding it yourself;<br />Do yourself a favor and at least tear it down. You will learn so much and enjoy learning from the experience.<br /><br />After tear down, post your findings here. There’s allot of great guys that will help you through the rebuild …<br /><br />Good Luck..<br />Bradster <br /><br />Ps. You said it was rebuilt 200 hrs ago but sat. The problem with having some one else do the rebuild is that after 10 to 20 hours break in, the heads need to be re torxed. Something that rarely gets done because the boat is out of the boat yard.<br />