1984 90HP Turns then locks up

[Faststroker383]

Hey guys search all over but haven't found an answer or even a possible solution to my problem...
I have recently purchased a bass boat with an 1984 Johnson 90HP J90MLCRD motor. When I brought it home I tried to start it and it would not turn over. The starter would engage but not the engine was locked. I tried again a second time to start and this time it did spin around several times (I'd say maybe 10 revolutions) then it locked up again. I then took out a socket and tried it by hand. I could rotate the engine about180 deg then it would hit something and stop. I could then rotate the engine back the other way and same thing would happen. I could definitely feel that something mechanical was interfering with the movement. I took out the plugs and still got the same results. I thought that there might be a piece of a broken ring jamming against the cylinder head so I took those off. I found no obstructions in the heads or scarring on the walls but even with the heads off I still get the same results...

I have no idea what the bottom end of this engine is put together but something is definitely not right in there.

Here is a video I took of the problem...

https://youtu.be/kNwRajNNIxY


Any suggestion before I remove and tear down the block?

 

[racerone]

Maybe there is water in the lower unit that is frozen.----Did you buy this unit without hearing it run ?

 

[oldboat1]

Pull the flywheel and look for an obstruction.

 

[ondarvr]

Could be something under the flywheel too.

​I shouldn't stop mid reply and nod off for a few minutes.

 

[gm280]

Maybe a rod cap come loose and is hitting? :noidea:

 

[Silvertip]

Bottom end problem. I will bet the prior owner said all it needed was a tune-up eh?

 

[interalian]

Since the lower unit is off and it's still doing it, I'd think there's a part loose inside the crank case. You can take the carb assemblies off and while you're doing it, look for any missing fasteners in and around the carb throats. Might have swallowed a loose bolt.

But do pull the flywheel first. Be sure to torque it properly (100-105 lb/ft IIRC) when replacing, and that the tapers are clean and smooth.

 

[Faststroker383]

Ok guys I'm heading home to disassemble the power head. I stopped by a Evinrude / Johnson specialist today and he suggested that most likely a rod bolt has worked it's way out. He did say that there could be something under the flywheel but based on how it feels and sounds I don't think that is the issue. I'll post pics of what I find though.

I haven't thought about the carbs sacking down a bolt though... that's an interesting idea. I'll be sure to keep an eye out for that too.

 

[interalian]

If a rod bolt has come loose, the rod will be scrap. But if it did, I'd think you'd see evidence of that piston hitting the head, especially if the bolt came out while the engine was at speed.

Do keep us updated - we really like teardown pictures!

 

[Chinewalker]

Is the lower unit off the motor? I couldn't tell in the video. If not, pull the lower unit before you dig into the powerhead.

 

[Faststroker383]

Yes I have already removed the lower unit.

 

[gm280]

I;m still sticking with either a rod cap that is loose but not off, or even broken but still holing on the rod to the journal with a portion of it yet. That would account for all your symptoms in my opinion. But that is just a wild $%# guess.

 

[interalian]

Since you already have the heads off, try turning the crank so one piston is on the upstroke, then turn it the other way until the piston starts to move down. Then press the piston top and see if it moves without turning the crank. This would indicate a major amount of play in the conrod 'big end'. Repeat for each piston.

 

[boobie]

Did you get any warranty from where you bought it ????

 

[Faztbullet]

Upper crank bearing has dropped needle/s and locks up on crankshaft counterweight....seen several do this...

 

[Faststroker383]

Do the brass screws in the intake need to come out to remove the intake ?

 

[racerone]

The power head has to be removed from the exhaust housing in order to take the engine apart.-------And I am not sure about brass screws in the intake.--------------The intake manifold is held on by about 10 / 12 bolts 1/4-NC around the perimeter of the manifold.

 

[Faststroker383]

I have the powerhead off and trying to remove the intake but can't get it loose. I have all of the perimeter bolts removed but still cant separate the two
Faztbullet... IF that is true in this case what am I looking at replacing? What damage could be caused by the loose needle bearing?

 

[racerone]

The intake manifold must be removed before you can take the crankcase cover off.-------The manifold hides a number of main bearing bolts -----If ALL the perimeter bolts are out then the manifold can be removed..------Can not count how many times I have done this procedure.

 

[Faststroker383]

After removing the powerhead I found this laying in the cowl... Any Ideas what this is? Is it even a part of this motor or boat?
https://goo.gl/photos/EX2AduF4J42SfHdq7