Wobbling crankshaft??

[model 10]

Bummer. The front seal has no real pressure on it, just crankcase pressure, which should not be much.

[Ten87]

Yep. Stinks. Eating into my re-fit budget for the rest of the work needed. Everyone I talk to says the same thing; "welcome to boating". Its to be expected I guess.

[MBWhite]

So how did the crankshaft get bent, lightning?

Let me preface this with the fact that I am on dial up at the moment and the browser bounces around a bit so apologies if I post something already written as it is hard to read the entire thread continuously.

Anyway, crankshafts do not just bend by themselves. So it either got bent somehow or the crank pulley is not on straight and the wobble is from the misalignment.

A couple of ways to figure it out, simplest but least accurate is to remove the pulley and replace just the bolt, turn over the motor and see if the bolt is spinning centered or moving around in a circular motion. If it is wobbly there then you can decide whether to see if you can straighten it yourself of if you want to send the crank out for professional straightening, rebalancing, and new bearings with a possible crank regrind. If money is a minimal obstacle to you that is what I'd suggest doing.

If worn bearings are the cause of your wobble I'd still strongly recommend sending the crank out for an inspection for any journal out of roundness and possibly magnafluxing for cracks.

However, if the crank has been bent due to abuse either by dropping something heavy on it or more likely someone using a hydraulic jack to lift the engine up and either overdoing it or forgetting to loosen a motor mount AND funds are short at the moment or you are in the middle of nowhere, it is possible to use a jack to carefully bend the crankshaft back to center. You will need to borrow or purchase a dial indicator with a base, but magnetic base indicators are available on ebay for $15 and up.

Straightening a bent crankshaft is not an undertaking to be casual about but it is within the abilities of most people who can pay attention to detail.

[Ten87]

Thanks for the reply:
It doesnt appear the crank is bent or wobbly as the tech put it; but after further investigation, doing exactly what you suggjested with just the bolt in the crank, its walking forward and aft, as well as while removing the balancer I could feel excessive vertical movement. Also no oil pressure. Motor scheduled for rebuild Aug 8th. Pulling it out this week. My guess is the crank will have to be machined or replaced at the least. Im sure a spun bearing or two has scored the journals along with other probable damage that a machine shop will have to handle. If i dont have it gone thru, I would never have confidence in it.

[Terra Nova]

Originally Posted by Ten87

...Motor scheduled for rebuild...My guess is the crank will have to be machined or replaced at the least...

Now you are getting up to speed.

[a64pilot]

Not the best thing to do, but I have replaced worn bearings on cranks before.
Pop off the cap, install a cotter pin in the oil hole in the crankshaft, when you turn the crank this will roll out the top half of the bearing shell. Polish the bearing journal on the crank with crocus cloth and insert the bearing shell covered in white lithium grease of your favorite pre lube.
I've done this on farm tractors where to remove a crank means spitting the tractor in half, course they were wet sleeved so I could replace the pistons, rings and sleeves with the block in place too.
If it starts well, the top end isn't hurt, and by all means while your there replace the rod bearing too, and think about a new oil pump.
Best to remove the engine and do a complete overhaul though
Course if it has spun a bearing your screwed, spun bearings though are pretty rare, often means engine seizure and a ruined crank

[MBWhite]

Originally Posted by Ten87

Thanks for the reply:
It doesnt appear the crank is bent or wobbly as the tech put it; but after further investigation, doing exactly what you suggjested with just the bolt in the crank, its walking forward and aft, as well as while removing the balancer I could feel excessive vertical movement. Also no oil pressure. Motor scheduled for rebuild Aug 8th. Pulling it out this week. My guess is the crank will have to be machined or replaced at the least. Im sure a spun bearing or two has scored the journals along with other probable damage that a machine shop will have to handle. If i dont have it gone thru, I would never have confidence in it.

Do you have an idea how many hours are on the engine? I totally understand the need to have confidence in an engine so I will just bring this to your attention and then you can form your own opinions-

It sounds like your problems are confined to the bottom of your engine. Before you remove it you may want to take compression readings on your cylinders. If compression is within specifications it is not necessarily mandatory to do rings and valves. Leaving the top end alone will not only be cheaper (may or may not be an issue) but it will definitely get you back on the water faster. Regardless of what you choose to do, as mentioned already plan on replacing the oil pump as that is a smart thing to do on most any engine that has had lubrication issues.

Good luck!