Is my motor toast?

[big_chief]

Looking for insights before I tear this apart...

I have a 1981 470 Mercruiser motor. It?s been running great for the last 6-9 months. I bought the boat after sitting for 1+ years.

I crank the motor once a week if I'm not using the boat... the other day I cranked it just fine, ran it 5 minutes and shut it down. As I shut it down, I noticed a small "click, clunk" as it powered down. I didn't think too much of it at the time...

So I go to crank it up today before a trip... and the first crank I get... "clack, click, clunk"... It tried to fire like normal... So I change battery over (crossing my fingers) and crank again... it goes about 1-2 revolutions... and SEIZES!

I say a few cuss words, hold my breath... and try one last crank hoping my starter just quit... the starter engages just fine, but the motor is seized.

I've done some minor work on motors when I was younger, my nothing major. I pulled the valve cover off... no cracks, nothing loose, nothing seemed lodged... all seemed okay.

What?s the best way to attach this? Its obvious, this is inside the motor at this point.

 

[dingdongs]

Re: Is my motor toast?

drive may be seized.pull and then see if its motor or drive.report back

 

[haulnazz15]

Re: Is my motor toast?

Pull the spark plugs and make sure there's no water in the cylinders, check the oil as well. If nothing it there, try cranking the engine with spark plugs out, or crank it by hand.

 

[big_chief]

Re: Is my motor toast?

A little more information.

The boat is out of the water. I last ran it in the water about 3 weeks ago... just fine.

I cranked the motor last week... it ran fine, except on the power down... motor made a funny noise.

Plugs are 9 months old. I pulled them, 2 were dry... 2 seems to have a slight bit of moisture (water). The actual plugs, were in decent condition.

I pulled the alternator belt, so there was no load on the crank.

So far, I have only tried to crank the motor about 6-7 times since these issues... trying to limit the amount of times I try to turn it over.

Interestingly, after I pulled the plugs, I tried to crank it again... IT TURNED NOW... made some clunking noises though. I tried again, and it would not turn. So I changed the battery thinking I needed more power. It turned again, but I noticed a slight "smoking" from the crankshaft balancer... I also noticed some small "chips" fly off. There is no load on the crank though. I noticed the balancer had about an 1/8 inch clearance from the C-ARM motor mount. I dont recall what the clearance used to be though.

I just replaced the oil about 1 month ago... It still has a light color to it... Can't tell if its still new... or if its water. Its looks fine though, dount its water. The old oil was dark black... didnt seem like any water was in it.

Not sure if that has anything to do with this... If not, my next step would be to pull the outdrive...

 

[Eric 3.7LX Alpha 1]

Re: Is my motor toast?

Wonder if one of the magnets came loose from the front balancer/rotor, and is causing getting caught on the stator inside of the balancer?

Do you still have the factory charging system or a belt driven alternator?

 

[EddiePetty]

Re: Is my motor toast?

............."It turned again, but I noticed a slight "smoking" from the crankshaft balancer... I also noticed some small "chips" fly off......"

...agreeing with Eric here: I too believe your stator just self-destructed and has jammed the crank pulley.

With the plugs removed, use a socket and breaker bar to rock the crank back and forth, see if pieces of magnets dislodge from the aft side of the crank pulley and the engine frees up some. If so, time to pull the dampener, remove the stator and make the one-wire alternator conversion.

 

[stonyloam]

Re: Is my motor toast?

Wonder if one of the magnets came loose from the front balancer/rotor, and is causing getting caught on the stator inside of the balancer?

Do you still have the factory charging system or a belt driven alternator?

I agree, pull the balancer. 470's don't die that easy.

 

[big_chief]

Re: Is my motor toast?

I keep thinking about the sounds I am hearing...

Its making more sense now. If I were to take a handful of chunks of magnet and steel and rub them together... this is sort of the sound I am getting.

The good news is I already have an alternator on the boat. There are 2 yellow wire that are capped coming out of the dampener area... I assume they went to the stator design the boat came with...

So I can just remove the stator altogether now, and leave it off?

I'm liking the way this is turning out. I'll let you know how it goes. Thanks for the insights.

 

[stonyloam]

Re: Is my motor toast?

So I can just remove the stator altogether now, and leave it off?

Yes, but the magnets are glued to the inside of the damper. Assuming that one or more are gone the balancer would no longer be in.. uh balance... So I guess you would want to remove the rest of the magnets and then maybe take it to a machine shop and have them rebalance it???? What do the rest of you guys think?

 

[EddiePetty]

Re: Is my motor toast?

Yes, but the magnets are glued to the inside of the damper. Assuming that one or more are gone the balancer would no longer be in.. uh balance... So I guess you would want to remove the rest of the magnets and then maybe take it to a machine shop and have them rebalance it???? What do the rest of you guys think?

...as the magnets were originally equally spaced to maintain alternating current, removing ALL the magnets should maintain balance.

 

[zbnutcase]

Re: Is my motor toast?

I keep thinking about the sounds I am hearing...

Its making more sense now. If I were to take a handful of chunks of magnet and steel and rub them together... this is sort of the sound I am getting.

The good news is I already have an alternator on the boat. There are 2 yellow wire that are capped coming out of the dampener area... I assume they went to the stator design the boat came with...

So I can just remove the stator altogether now, and leave it off?

I'm liking the way this is turning out. I'll let you know how it goes. Thanks for the insights.

Yup, disassemble, pitch the stock stator, remove the magnets, reassemble, go boating!