Chrysler 55hp 1973 compression issue

[modopopcorn]

Hi guys!

I'm having some problems with a Chrysler outboard that I got with a boat a couple of weeks ago.

The previous owner said that after his kids was out playing and pulling water-skis with the boat and the line got tangled in the propeller the engine started to running poorly. He described it as the motor felt tired and weren't able to rev as usual.


This was all the information I had when I bought the boat and started tinkering with it. A new propeller was included with the boat and it was the first thing I swapped out. Then I cleaned out the carburetor as the boat had been sitting for a couple of years. I got the motor to start but I wouldn't idle well and stalled easily.

Took the boat out for a quick test and the symptoms were still there as the previous owner described them.

I checked the compression and the upper cylinder showed 150 psi, a really good number for an engine as old as this one, but... The lower cylinder had 0 psi. I removed the cylinder head and the head-gasket was shredded to pieces.

I managed to get hold of the only head-gasket available in Sweden and installed it today. I still get 150 psi on the upper cylinder but I only get about 30-50 psi on the lower cylinder.

I tried letting the lower cylinder sitting in oil for like 15 minutes and then the compression went up to like 70 psi but the next test it was down to 50 psi again.

I believe it's a stuck piston-ring as the cylinder looks fine on the inside. I can't feel any excessive play in the piston though.

Do you guys have any idea what could cause this difference in compression? I tried taking the plates next to the fuelpump of an from what I could tell the rings looked fine but tbh it's hard to make a diagnosis based on this.

I've tilted up the motor, set the lower piston at almost tdc and filled it up with engine oil, will let it sit over night.

 

[Nordin]

I think you have score at the piston at the exhaust side.
It is the side that is really hot, the fuel pump side can look good but the other side has damage.
Send me a PM and with your phone number.
I am in Sweden too and maybe the only one that know and work on Chrysler OB.
It seams nobody are willing to put their hands on them.

 

[modopopcorn]

Thanks Nordin, I've sent you a PM. Yeah, spareparts are hard to come by and people with knowledge and skill is even harder these days.

The motor has been sitting with oil for about 14 hours now, will go outside soon and start tinkering some more, probably pulling the head off one more time.

 

[jerryjerry05]

Sounds like the rings are seized ??
The bottom cyl. runs the fuel pump, it sets on the lower port cover(4 screws)
Remove this and you can see if the rings are carboned up?

 

[Nordin]

jerryjerry I have spoke to him on the phone and there are score in both cylinders at exhaust side.
Bottom seams worst and the rings are stuck in the piston cause of overheat and maybe lack of oil.
Top has also score but rings seams to be free.

 

[modopopcorn]

Hi guys, ended up tossing the motor in the garbage, felt like it was way to much money to spend on an engine that was so worn out and old. So I've bought an Mercury 500 -1970 instead

 

[jerryjerry05]

SELL the parts.

 

[modopopcorn]

Not much interest in old Chrysler outobards in Sweden I'm afraid. And what's even worse is the shipping-rates, even a small and relatively light item easily costs about $10 to ship even if it's only to the neighboring town.