1979 Chrysler 85HP: Piston Damage, need advice please

[jombee]

I replaced a broken head gasket 2 months ago and the motor has been running perfectly and used every weekend since. Last weekend after arriving back at the dock at the end of the day, it would not start up. When I got home, I tested compression and 1 cylinder was down to 45, so I assumed the gasket blew again. When I opened up the head, I found that a small piece of the top of 1 piston was broken off, and there was damage to the piston, and I assume rings (see pictures). I do not see any damage to the cylinder wall. My question is how is best to proceed. Replacing a piston and rings is above my skill level, I don't have the proper tools or workspace. I have yet to find a local shop that is even willing to look at or work on my engine. I would love to get this fixed if I can for a reasonable amount. Any suggestions would be appreciated.

 

[Redbarron%%]

Is there damage to the head as well?
Perhaps there is a piece of reed valve broken off and it passed through the cylinder with relatively little damage.
It doesn't look like the engine ran for long after the damage as there looks like there is no soot etc on the areas.

Perhaps others have a better idea.

 

[Tassie 1]

You have to remember it's nearly 40 yrs old,
What will a rebuild cost compared to a newer outboard?

if my 1979 70 hp cacks itself l won't be rebuilding it

 

[jerryjerry05]

I don't know if the reed would do that much damage.
They're pretty flimsy and would go through and out the exhaust.

Take the side covers off and see if there is damage there?

Where do you live?
Fill out a signature and include home port, boat specs.

Not mechanically inclined: get a different motor.
Lots of stuff for sale on Craigslist, depending on the area.
ANY Force/Chrysler will swap over easily, the other brands not so easy.

Since it didn't score the walls, the block can be used again.
The piston? no

 

[racerone]

The cylinder wall looks to have slight scoring.------Take it apart.-----Measure the cylinder .----Then see if you want to spend the coins.

 

[Redbarron%%]

If it were me I would pull the transfer port cover on the left side and take a look at the rings in the intake port. If you can press on them and they spring back they are not broken.
The piston should wiggle in the space of clearance around the piston.
You can also look for trash in the transfer port and look up into the space behind the reed valves a little to see if there is anything there.
I did not see enough scoring to drop the compression to 45 lbs.
There are many here with more experience on two strokes than me, but I would also pull the intake manifold behind the carbs to tale a look at the crankcase intake side. (at least on the 90 hp Force it is).
The damage looks like it is from FOD (foreign object damage) and not preignition.
If it is shiny and bright and looks like something damaged the top of the piston the skirts and the rings may be OK and your problem can perhaps be fixed if you can locate where the object came from. (If I am correct about the damage).

 

[racerone]

??-----That damaged piston ran hot, very hot.-----Tear this motor down for inspection and repair.-----Beyond your capability you say, then this will be a free education.

 

[Redbarron%%]

Looking more closely it could be a burned piston with ring failure on the exhaust side, but the picture could be clearer to tell for sure.
Initially it looked to me like something hit the top of the piston, but I can be wrong.
If it is a matter of experience you can learn a lot by tearing it down to see what happened.

 

[Tassie 1]

Where do you live?
Fill out a signature and include home port, boat specs.

how does someone who ain't too bright ( me! ) do that again?
was easier years ago but buggered if it'll work now
cheers

 

[jombee]

Hi Everyone, thanks for replying.

There is no head damage

I live in Connecticut, I do not see how to setup a signature

Boat: 1979 Chrysler bassrunner 85, original motor, Chrysler 85hp Model T850H9A Serial 1074

To me, it looks like something hit the top of the piston, a small piece is missing.

The water flow has always been strong, and I never heard any overheat warning.

In addition to my lack of skill and tools, I do not have a workspace (garage, etc.) to tear this down myself.

Also, I'm very unsure about the parts/tools I will need, and how to diagnose what caused this to happen.

I see 3 different piston sizes and ring sizes for my engine

https://www.*****************/parts/c...aft-and-piston

Std, .010 & .030. Am I to assume I need the standard sizes?

My son and I use this boat to fish every weekend and needless to say we are both devastated over this.

 

[jerryjerry05]

The piston in the motor are standard size pistons.
If you bore out the cyl. then you get into oversized.
Your pic shows no damage, so you'll need a standard piston.

You need special tools to put the new piston together.
So a Wiseco piston will work best, no tools needed.
Get the whole kit, rings and wrist pin.

Get new rings for the other cyl.
Wiseco ring only fit their product.

The FIRST thing you need is a FACTORY manual.
Get one for your year or one real close to yours.

The cyl went bad because of: the carb set wrong, the recirc system clogged, sucking air, bad gasket
timing off, any number of things???

 

[jombee]

Thanks Jerry

I think this repair is beyond my skill level, in addition to not having proper tools or any indoor workspace.

I've got a Seloc Manual, but I assume you are referring to something else.

If I look for a replacement motor will any year 85hp Chrysler or Force swap out easy?

I'm concerned about the ease of the swap; electronics, control cables, hoses, trim/tilt, etc.

 

[jerryjerry05]

Just about any Force until 1993-4 should swap easily.
Just make sure the motor is the same length???
They made them in 2 sizes 20 and a 25"
Measure the center of the transom from the top to the bottom .
Most of the older Chryslers were 20" so make sure the replacement isn't too long.
You can post pics of your mid section with the drive and we can tell if it's the right size.

The 79 used screw down transom clamps.
They stopped them in 86/87 and went to a through bolt system(much better).

It's still fairly easy to mount if the bolts were used.

 

[jombee]

Hi Jerry

I'm not exactly sure about the length, where i'm supposed to measure from. I've attached a few pictures

I would like to make the swap as easy as possible.

I've seen a few used motors listed, but most don't seem have power tilt/trim like mine does.

Is this something I can somehow still use with another motor?

 

[Nordin]

Jombee that is a 20 in engine, so you need a 20 in if you swap the whole OB.

You can swap the power head with any Chrysler 3 cylinders 70-90Hp or Force 85-90Hp earlier then 1994-95.

Pulling the T/T from your 85Hp and mount on another Chrysler/Force can be a big job.
Most bolts and stuff can be corroded if it has been in salt water.

 

[jombee]

Thanks Nordin!

I am going to swap the whole OB with another OB for sure.

Where exactly do I need to measure from to be sure I am buying a 20?

Also, I have screw down transom clamps, so I assume I need to be sure the replacement is the same, correct?

I've never had this boat in salt water, but I've only had it for 3 years.

 

[Nordin]

You measure from the edge of the transom clamps where it hooks over the transom and to the anticavitionplate.
It is the big vertikal plate above the prop.

This distance should be just about 20 inch.

 

[jombee]

Got, it! Thanks Nordin

Regarding the clamp though, I would need the same that I currently have, screw down transom clamps, correct?

 

[jerryjerry05]

No you don't need the screw down clamps.
You can use the through bolts.

The bottom hole on both clamps should line up.
Install the motor,
Install the bottom bolts and loosely tighten them.
Make sure the motor is against the boat.
Then using a 1//2" drill bit, cut the new holes.

BUT!! before the top holes get cut, make sure the cavitation plate is even with the hull.
It should be close but if too high you need to lower.

 

[Nordin]

Have to correct myself about the anticavitation plate in my latest post.

It is the big horisontal plate just above the prop, NOT vertikal as I wrote !!!!!
Sorry, sorry an logical error.