1988 ERude 90 Crankshaft / Rod question

[gr8rg8r]

My 1988 Evinrude 90 had been performing flawlessly. Today, while at about 2000 rpsm, there was an occasional clunking sound and then the engine shut off. I could not turn the flywheel.

At home, I took off the heads and the cylinders seem okay. I can turn the flywheel counterclockwise several rotations, but if I turn it clockwise, there are some "rough spots" where the engine is more difficult to turn and at other times the flywheel will not turn any farther clockwise. If I then turn it clockwise, it feels rough for a little bit and then feels smooth.

Broken crankshaft? Broken rod?

If I was committed to keeping this engine, I would tear it down and find out. But, before investing the time on a 19yo engine to tear it down, I would like some ideas on what others think it could be.

Thanks in advance.

 

[gregr1971]

Re: 1988 ERude 90 Crankshaft / Rod question

if you decide to repair it, i have a crank, and rods for it, and all of the powerhead, the motor lifted a ring, everything else is perfect.

 

[Silvertip]

Re: 1988 ERude 90 Crankshaft / Rod question

Pull the flywheel. Perhaps one or more magnets came loose and are catching. Could also be a broken ring catching on a port.

 

[Silvertip]

Re: 1988 ERude 90 Crankshaft / Rod question

Pull the flywheel. Perhaps one or more magnets came loose and are catching. Pull the exhaust covers and have a look through the ports. A piston could have shed a skirt and any scoring on that side of the piston would be viewable.

 

[flabum]

Re: 1988 ERude 90 Crankshaft / Rod question

I doubt that it is a flywheel magnet because of the design of the flywheel. I would pull the gearcase first. Sounds more like a busted pinion.

 

[Joe Reeves]

Re: 1988 ERude 90 Crankshaft / Rod question

As FlaBum above states, drop the lower unit to determine whether the binding is within the lower unit or the powerhead.

 

[gr8rg8r]

Re: 1988 ERude 90 Crankshaft / Rod question

Update: I dropped the lower unit and the flywheel is stilll binding. Should I remove the flywheel next?

 

[noelm]

Re: 1988 ERude 90 Crankshaft / Rod question

if the heads are off, then it should be rather obvious if a Rod is broken! one piston will not be moving, it sort of sounds like a rod bearing may have died and is catching as you turn the crank, but without further "surgery" then we can only guess.

 

[gr8rg8r]

Re: 1988 ERude 90 Crankshaft / Rod question

if the heads are off, then it should be rather obvious if a Rod is broken! one piston will not be moving, it sort of sounds like a rod bearing may have died and is catching as you turn the crank, but without further "surgery" then we can only guess.

If it's a broken piston rod, wouldn't the piston be forced up with the head off and not prevent the crankshaft from turning?

And, should I bother removing the flywheel?

Finally, if it is a crankshaft or rod problem and the pistons are okay, could I replace the crankshaft or piston rods without removing the powerhead? Would you recommend that? The compression was fine, the engine is a 1988 and I would like to squeeze another year or two out of it before droppig 6K on a new Etec.

Any suggestions are very welcome.

 

[ezeke]

Re: 1988 ERude 90 Crankshaft / Rod question

Take the spark plugs out and use a wood pencil to "feel" the pistons as you turn the flywheel. The problem piston will reveal itself. You can then decide if you want to examine it through the bypass plate or cylinder head or both. Get the proper gaskets first.

 

[Chinewalker]

Re: 1988 ERude 90 Crankshaft / Rod question

There is no way to replace a piston or rod with the powerhead intact. It must come apart. At this point, it won't cost anything to disassemble the powerhead to find out exactly what the issue is. As was stated, the flywheel is more than likely not the problem, as the magnets are cast into it, unlike later ones that have them as a seperate part epoxied or bolted into place. If you don't want to get into a full teardown, you might be able to see what's going on by removing the intake manifold. You can see the rod caps when that is off...
- Scott

 

[gr8rg8r]

Re: 1988 ERude 90 Crankshaft / Rod question

Thanks folks! I guess I'll be doing some dissecting in a couple of weeks...

 

[gr8rg8r]

Re: 1988 ERude 90 Crankshaft / Rod question

Update: I finally got around to tearing this engine down. The lower crankshaft bearing was obliterated and was wobbling and catching and binding.

Here are pictures:

http://www.elbrasil.com/evinrudeengine/pictures of engine.html

So, here is my plan:

1. Replace the crankshaft bearing. The housing (race?) for the bearing seems to be intact.

2. Disconnect the piston rods, pull out the pistons, hone the cylinders, and replace the piston rings. Compression was okay before this bearing went bad, but it is easy to replace the rings at this time.

3. Thoroughly clean to remove all the shavings.

Reassemble.

What am I missing?

 

[gr8rg8r]

Re: 1988 ERude 90 Crankshaft / Rod question

bump