Piston play, what should I do?

[DamianJP]

Hey guys

Well I'm kinda bummed. I went to prep the area to put back the cylinder cover and when I was done I found that the bottom piston has play in it , top is solid with no play but looks like it might be worn too. You can see me move the bottom piston side to side with my fingers. Also when you rock the flywheel back and forth you can see the play too.

Compression was high on the bottom one which is weird. I think 120+ I forgot the exact number. Top one could not be taking because of a blown cylinderhead gasket letting Cyl 1 combustion into cooling area. Cylinder walls are both very smooth and no signs of 'bad' contact anywhere.

What should I do? Either I run it like it is or have to dig in and replace bearings and rings (Or do I need new pistons now too?) Money is tight and this is a real bummer. What are my options and how much would It cost to do the rebuild (Bearings and rings ect. Everything that should be replace while I was in the crankcase area?)




Thanks,
DamianJP

 

[yorab]

Re: Piston play, what should I do?

I've been told that some play is normal at the crown of the piston. The skirts are tighter. The sleeves are steel and the piston is aluminum so they have different expansion rates. Therefore, they shouldn't be tight at room temperature. I'm not sure how much play is acceptable though. Could depend on you particular block. I'm not an expert but this may give you a bit of hope until a true expert rings in here.

 

[DamianJP]

Re: Piston play, what should I do?

Thank You Yorab

Well hopefully your right. I mean I really like to work on outboards and all. Never replaced pistons and stuff before but it would be fun and rewarding after it is done. But money is real tight and this might be put on hold for a long time. Compression was real good on that cylinder, but I don't know why the top cylinder is tight and not moving like the bottom one.

Anyway hopefully like you said, there might be a small chance of hope. I know it's a 77' and it probably needs a rebuild sooner or later , it's just a bad time.Mabey some one thats been threw this can chime in.



Thanks,
DamianJP

 

[F_R]

Re: Piston play, what should I do?

I really can't tell if the play is within normal limits, but it is true that the top end of the pistons is smaller than the skirts and will flop back and forth. Clearance is measured at the skirt, shich of course is inaccessable witout tearing it down.

Having said that, the one with no play probably is the bad one. The rings are probably stuck in the grooves, preventing the piston from flopping back and forth. Didn't you say that one has low compression? At the least, the stuck rings may free up with some de-carb treatment. At the worst, the rings will break and that is that.

 

[Big flop]

Re: Piston play, what should I do?

As stated above some play is normal. Good compression,
no knocks or rattels before it probably will be ok.
However the top piston with no play might concern me?
Blown head gasket, with any water going into cylinder that
has sat any length of time exposed to the air may cause
a problem with wrist pin bearing or rod bearing? (no play in piston)
With just the price of a head gasket being cheaper then
a rebuild I'd put it together & see how it runs
The above post was not there when I started this
I had to stop half way thru
Sorry.

 

[DamianJP]

Re: Piston play, what should I do?

Heres how it went. My nephew was running my fathers boat and I noticed that the 'pee' stream started to look funny so I told him to head in. By the time we got back(5-10min run) it was pissing water then steam, water then steam on and off. When I dug into the cylinder head area thats when I noticed the gasket was blown out and letting top cly combustion into the water jacket area and I guess water into the combustion chamber area because the plug at the top and piston was steam cleaned.

Top cylinder I could not get a reading, because of the breach into the water jacket.
Bottom cylinder is the one with play and it had over 120 PSI compression.

Could the water intrusion lightly rusted the rings making them stick? The plug on top cyl had light rust on the end. Any which way it takes loads of my brain and the new focus is to un stick the top cyl rings. Whats the best way, run sea foam thru some tanks of gas, and how will I know if the rings free up or not with the cylinder head on? Is there a way to unstick them with the cylinder head off so I can feel the piston when they free up?


Thank You Yorab, FR and Big Flop
DamianJP

 

[F_R]

Re: Piston play, what should I do?

I hate to tell you this, but I don't have a good feeling about that motor.

OK, let's face the facts. That motor has been run hot. Hot enough to blow the head gaslket. That means the exhaust cover gasket is burned also. So, like it or not, the powerhead has to be pulled and the exhaust cover gaskets replaced and parts checked for warpage. If you don't do that, water will squirt into the cylinders from the leaky exhaust gaskets.

With the exhaust covers off, you will be able to see one side of the pistons (the hot side), and be able to access the damage. Good luck.

 

[DamianJP]

Re: Piston play, what should I do?

Hey FR

Well, thats a bummer. I did buy the 2 headgaskets and 2 exhaust gaskets when I bought the other stuff so I guess it's good I grabbed them. Only thing is the power head bolts are in bad shape, might have to cut some of the heads off and heat/vise grip the studs out.

Ill check it out tomorrow , but you are certain that I should start the power head pulling and replace the 2 exhaust and 2 head gaskets?

What parts should be checked for warpage?

How heavy is the power head? Dry weight of the whole motor it 185, so the head should be around 100Lbs?

Thanks for the help so far.


Thanks,
DamianJP

 

[jbjennings]

Re: Piston play, what should I do?

You're getting help from the best there is, but I'll add my 2 cents, anyway...
This is a '77 model what??? I just didn't catch what engine you're working on.
If F-R says pull the powerhead, you might as well buck up because he's usually right. I think you should pull the powerhead AND split the halves and find out for yourself how bad it is, because it really doesn't cost much to do it. Powerhead to base gaskets aren't high and there is no gasket for the engine halves usually. Then you could pull your bad piston and see if you can get the rings loose or at worst, replace the rings with new ones. You could also make sure there's no rust on the crank journals and rod bearings and such. Make sure you have a good torque wrench and torque everything properly. If the rings are stuck sticking out (and it sounds like they might be), I'm thinking they will scar your cylinders, or even worse the rings could break and GOUGE the cylinders and it'll be pretty much game over unless you want to spend money on oversize pistons and a rebore.
BTW, you'll probably have to pull the powerhead anyway to check the upper water tube grommet which could be melted. And of course, find out why the water pump or thermostat failed and fix that!
You can put the head on a piece of glass and check for warpage. If it's warped, a figure 8 motion on some 400 grit sandpaper on the pane of glass can help true it up if it's not too warped.
Just something to think about.....
JBJ

 

[DamianJP]

Re: Piston play, what should I do?

Hey JBJ

First off Thank You. Every little bit helps.

Its a 1977 Evinrude 55HP 55773D

I did the water pump and carb job already. Just got done installing new thermostat and pressure relief valve/spring and torqued the bolts down for the water cover on the cylinder head. I didn't check that for warpage tho , yet. So i might have to take the water cover off the cylinder head i guess, and need another gasket. Or just check the side that mates with the cylinder block/engine ?

I have the water tube upper gromet/seal and plate, also have the 2 gaskets that go inbetween the mid section and powerhead. Also have the 2 exhaust gaskets.

When I took the water pump apart it looked fine. The Thermo was abit nasty salt/crap build up. I thought the cylinder head gasket just blew from old age. But when they blow its usually from an overheat?

Again Thank You !


DamianJP

 

[F_R]

Re: Piston play, what should I do?

jbj raises some good points. But if it were me, on my motor, I would do as I suggested: Remove the exhaust covers and take a look to see what you are dealing with. Since it has been overheated, there is a high probablility that the pistons are scored and stuck rings. But look and evaluate before freaking out. Always time to freak out later.

Warpage of the cylinder head-to-block is likely. Warpage of the cylinder head water cover usually is not a problem.

You can lift the powerhead, although I always used a hoist--partly because I had one, and partly because you can control what you are seeing and doing if not bear hugging it.

 

[DamianJP]

Re: Piston play, what should I do?

Hey guys

Well got down to the boat today. Got all 8 bolts out (1 head broke ,but ill get it out) CRC Freeze out is awesome. Also got the shift linkage bolt that hold the shift coming from the L/U out. And the 1 aft nut at the back. The power head doesn't want to separate from the adapter plate. Now if I take the 2 screws out holding the adapter plate down she'll move abit with space between the adapter plate and the mid section but the power head won't separate from the adapter plate.

Driving me nuts. Mind you me and a buddy were lifting on a steel bar that we hooked to the lifting eye so mabey I need to get a engine hoist from harbor freight for $150 .
Is there anything I'm missing to disconect.

Also what a good way to check for the warpage with the glass? Any tips / tricks?

So far this is whats disconnected off the powerhead...

8 bolts
1 Aft Nut
1 Shift linkage bolt that holds the shifter from the L/U
4 Cowling bolts
Shift and throttle cables
Starter and harness
Also dropped the L/U

Hitting it up tomorrow early.



Thanks again !!!,
DamianJP

 

[DamianJP]

Re: Piston play, what should I do?

Hey guys

Made some progress, and Im slowly 'climbing' out of some pitfalls along the way. Got her broken down and the walls and pistons look real good (to me) and only 1/4 to half of the ring closest to the cylinderhead is stuck, rest of that ring is floating good.

The damn tube/shaft that goes from the steering arm down thru the transom bracket to the bottom of the midsection mount housing was really rusted and when I went to get the snap ring off the tip crumbled, and quite easily too. Good thing it happened here and with the engine broken down so I can replace. I think I might have a guy close to me who has tons of Johnson/evinrude parts so say a prayer. If not anyone here have a total mid section/transom mount (adapter plate and down) laying around they want to sell?

Also one of the wrist pins move freely if I push it with my finger, the other is stationary is this a problem?

How can I tell if I need needle bearings and the other bearings? Is it some you just replace when you open her up this far?

Camera is down right now but as soon as its charged expect some pics mabey a small vid. Cylinder head place is the next stop to see if it just needs rings , if it need a bore and new pistons Im afraid Im might have to fold my hand and search for a new motor. Paid $475 for the engine and already have $250 into it. Not to mention another shopping cart list for around $300 for the other gaskets/seals and new bearings/rings. What do you guys think, hang in there and get new pistons and stick with her if need be?

Thank you all so far who have to here my endless rambling and questions, all the advice and help is pricless and I love to learn (sometimes the hard way) and enjoy the final product.

T H A N K Y O U,
DamianJP