What did I do wrong?

[eavega]

I have (had) a 1972 50 HP Evinrude Model 50273C. Compression, checked, 125 dead even on both cylinders. Spark, check. Fuel, check - from tank to carb. pump the bulb until needle valve closed off fuel to the carbs. Timing, checked at 20 degrees WOT (Spec is 19 degrees +- 1). Temperature, check. You could lay a hand on the cylinder, 120 degrees by non-contact thermometer after 5 min WOT running. water dumping over exhaust ports as expected. fuel mix 50:1. Motor running 5500-6000 RPM which is its operating range per the manual (Manual says 5000-6000 RPM). Today, on its fourth trip out, it blew a hole in the cylinder block. Engine is toast. I was able to limp back to the dock on one cylinder. I could see exhaust leaking through the breach in the cylinder block. I don't even feel like tearing the motor apart to see what damage there was to the piston, rods, etc. Now I have to go and part this motor out to build up a budget to re-power my boat. My question; what did I do wrong here? Why did this engine fail? Granted, I had just purchased this motor a year ago, and had to take the word of the previous owner that it was maintained, but I tore into it and found that they carb gaskets were all new, the impeller was in good shape, so I had no reason to doubt that the motor was not maintained.

It is just so frustrating. I have worked for the last 4 months every evening to make sure the hull was in good shape (I had verified the working condition of the motor before I began the hull work), just to have the engine fail on me on its 4th outing. I'm back to square one now. Hopefully I can sell the valuable parts of this motor (the controls and the lower unit, since it is a hydro-electric shift, and the starter, ignition system etc) for at least enough to get me onto another motor that may stand the test of time.

This is in part a vent post, but also a question as to what I could have done to prevent this catastrophic failure of the motor.

Rgds

Eric

 

[Daviet]

Re: What did I do wrong?

Hard to tell what happened until you tear it down. To it sounds like a rod cap broke and when the crank came around it knocked the rod out the side of the block.
Could you post a picture of the damaged area.

 

[jonesg]

Re: What did I do wrong?

Weak casting, it happens, forget it.

I would avoid those elect shift models because parts are rare as chickens teeth.

 

[Bifflefan]

Re: What did I do wrong?

Thats rough, I feel for you.
After building many, many engines. I can say with all certainty that some times they just break.
I've had race engines go 2 seasons and not miss a beat, then one season we (the team) went through 14 engines in one season. This was corrected by not using the engine bearings we had been using that year.
I've seen brand new engines expire on the dyno after 5 mins of running.
You can find the cause, but I would guess age may be a factor.

 

[bktheking]

Re: What did I do wrong?

The motor is almost 40 years old, who knows what life it lead until you bought it, that "why" question would be tough to answer.

 

[tx1961whaler]

Re: What did I do wrong?

Don't be too hard on yourself. It does not sound like you did anything wrong. That's a 38 year old motor and something just decided to let loose. No telling how is was maintained and run over the last 37 years......

 

[Rudi2]

Re: What did I do wrong?

Don't be too hard on yourself. It does not sound like you did anything wrong. That's a 38 year old motor and something just decided to let loose. No telling how is was maintained and run over the last 37 years......

Agree with that, no reason to wonder why now. Hope your next one is better, when you are dealing in 30+ year old motors you are just taking a chance - simple as that. Staying away from electric shift is good advice also.

 

[eavega]

Re: What did I do wrong?

Here is some pictures of the fatal damage.

A long shot of the engine. You can see the hole on the inside of the loop that the fuel line makes.

Here is a close-up of the damage.

I'm still just angry. Another fall fishing season out the door while I get a motor to re-power my boat. UNGH!


Eric

 

[Dhadley]

Re: What did I do wrong?

You have nothing to lose by taking it apart and finding out what happened. It didn't hurt the mating surfaces so the block is - most likely - savable.

 

[Daviet]

Re: What did I do wrong?

Yep, tear it apart, looks like a rod let go. If the crank is not damaged you might be able to save it.

 

[eavega]

Re: What did I do wrong?

Okay, I guess while I am trying to divest myself of some possessions in order to fund a new motor, I might as well tear into this one to either fix it up or part it out.

I started breaking it down today, and was defeated by the flywheel nut. Who knew there was actually a 1-3/8" nut?!

Anyway, I did start removing some of the peripheral motor components (fuel pump, carbs, starter). I pulled the spark plugs and got curious to see if the bottom piston (where the damage is) was still moving. I slowly turned the flywheel by hand, and noted that the piston was still moving as expected, and even gave a good "Chuf" of pressure as it came to the top of its travel. I put my thumb over the spark plug hole, turned the flywheel again, and got a good pop from the piston. This gives me a little hope that it can be fixed, since the piston seems to be intact and still attached to the connecting rod (The piston and wrist pins for this motor are obsoleted, and there are no alternatives. Everything else in the crankcase is showing available).

I'll post pictures of the progress as progress is made.

-E

 

[1946Zephyr]

Re: What did I do wrong?

I would hunt down a good, used powerhead, or even a reman. You should be able to find one of these at a reasonable price, since it is an older motor. There should be lots of them around. It would be a lot cheaper than buying a new motor and you won't have to make any changes to your set up, at all.

Obsolete? Hah! There are still lots of parts for that old bugger. It's just a matter of where to look. Try these places and see what they tell you.

sea-way.com
engine blade and prop.com
outboard-parts.com
laingsoutboards.com
tcoutboard.com
fairwindsmarina.com
salvagemarine.com
marinepartsoutlet.com
outboardexchange.com
Superior Marine (800-338-9281)
budgetboats.net
americanoutboard.com
piratemarinesalvage.com
trixieslanding.com
mmmarinesalvage.com
tcoutboards.com

You can even try the aomcia website. This is new stuff to these guys and they likely can help.

 

[samo_ott]

Re: What did I do wrong?

That's seems odd that it seems to have compression. But that's a small hole. Nothing that some JB weld coudn't fix if you can find and fix the original problem.

 

[eavega]

Re: What did I do wrong?

That's seems odd that it seems to have compression. But that's a small hole. Nothing that some JB weld coudn't fix if you can find and fix the original problem.

I can always hope that there is no real damage other than the crankcase. The motor did get me back to the dock a couple of miles away, although the RPMs didn't get above 3000. If it turns out that the motor is repairable, I am gonna have the crankcase repaired by a local welding shop. Owner is a neighbor and I trust he will do a good job.

-E

 

[tx1961whaler]

Re: What did I do wrong?

I can always hope that there is no real damage other than the crankcase. The motor did get me back to the dock a couple of miles away, although the RPMs didn't get above 3000. If it turns out that the motor is repairable, I am gonna have the crankcase repaired by a local welding shop. Owner is a neighbor and I trust he will do a good job.-E

I've gotten lucky before. I had a rod just break in half and come out of the side.
It did no apparent damage to the crank or cylinder, so I cleaned it up and put a new rod in (did all of the bearings and rings while it was torn down), got it welded and ran it for a few seasons until I got sick of the electramatic gearcase and traded it.

 

[jmendoza]

Re: What did I do wrong?

It may be a busted ring or a chunk of the piston skirt broke off and got into the crankcase then jammed by the crank against the case and busted the casting. Or, you could have had a piece of FOD (foreign object debris) like a nut or bolt get inhaled into the airbox and into the engine.

 

[eavega]

Re: What did I do wrong?

It may be a busted ring or a chunk of the piston skirt broke off and got into the crankcase then jammed by the crank against the case and busted the casting.

Give that man a cigar! I finally broke down the power head, and lo and behold...

When I got the case off, I also found a big ole hole got knocked into the case

So, given that I would now need a replacement piston, is it worth pursuing a welder to fix the big hole and the smaller breach in the crankcase?

Also, I guess I am looking for some post-mortem opinions on what happened here. The rings are still intact and apparently not stuck. The cylinder wall is not scored (at least, not as far as I can tell using just eyeballs). I think there is one small abrasion on the broken piston. The cylinder walls seemed well lubricated, as did the piston itself. The connecting rod looks fine, with the exception of an abrasion where it probably pushed the piece of piston skirt through the crankcase. Is this just a case of metal fatigue and the piston failing? Here is a side by side shot of the top piston that was still working, and the bottom piston, which is the one that failed. Does anyone see any clues as to what might've happened here?

I've already secured another motor (70 HP Johnson) , so I'm just going to part this bad boy out. It seems a shame, since I had it running so well. Obviously, though, it was not as healthy as I thought.

Rgds,

Eric

 

[samo_ott]

Re: What did I do wrong?

Almost looks like you could reuse that piston! (I wouldn't but it almost looks like you could!)

 

[MTboatguy]

Re: What did I do wrong?

The piston that broke, almost looks like it was heated way up one time or another, the color of the rod looks to be off, which might be what caused the metal fatigue...

 

[1946Zephyr]

Re: What did I do wrong?

Hell, I would go ahead and rebuild it. Tearing it down puts you half way there already. Just replace both of the pistons, hone the cylinders out and fix the holes in the crank.