Compression 1959 sea king 35hp

[42 Clyde]

I have a 1959 omc sea king 35hp outboard. What should i be getting for compression? I have checked with 2 seperate guages and i only get 90 psi in both cylinders. That seems low to me.

 

[F_R]

Can't say that I know in numbers. But a question for you---are you checking it with the recoil starter? If you are, have you disabled the compression relief?

 

[42 Clyde]

The compression relief is disabled. Im using the electric start for testing compression.

 

[racerone]

Remove bypass covers and inspect pistons & rings.

 

[42 Clyde]

I replaced the piston rings and head gasket. All the measurments wer in spec. Ring gap, piston to bore gap, bore diameter and the Pistons wer in good shape. All the measurments wer on the high end of the tolerance but they met tolerance. It just seems that 90 psi is a little low.

 

[racerone]

Just run this motor.----It should run like a charm with new rings.

 

[42 Clyde]

Thats the problem. Im trying to run this motor on my restoration project. But it doesent run well and im at a loss to figure out why.

 

[iggyw1]

Thats the problem. Im trying to run this motor on my restoration project. But it doesent run well and im at a loss to figure out why.

It would help to tell these gurus what the motor is doing or not doing. You said it does not run well, so let them know what you are not happy with and they will give you more help.

 

[42 Clyde]

The motor runs very poorly and never gets up to full rpm. I have narrowed down the culprit to the bottom cylinder.
The motor will run fine on the top cylinder alone but not run at all on the bottom cylinder alone. Compression is equal between both cylinders. I have tested every piece of the ignition and swaped the pieces one by one to narrow down any ignition problems. Spark is hot and on time. Read valves look brand new and meet specs. No light coming through the reed valves. Crank case is not leaking. Head gasket is brand new. All the gaskets are brand new. Basically I just need to know what I’m overlooking. Back in the day I was trained to build aircraft engines but this little two-stroke is making me feel stupid. I’m sorry if this sounds like a rant. I’m on lunch and a very little time to type.

 

[racerone]

How did you assemble the carbon seal on the bottom of the crankshaft ?----From where I sit you might have a crankcase compression issue.----Or bring it over as I think it might be an easy / simple fix.

 

[lindy46]

My 1957 Evinrude Lark had compression of 125psi in both cylinders. 90psi sounds low.

 

[42 Clyde]

I had the same idea about the bottom seal late last night and removed the motor from the leg. I used the fuel pump pulse port to put a little air pressure into the crank case lower side. The seal will hold back a few pounds of pressure but not much.
The carbon seal or “ quadrant seal”, is definitely one of the seven wonders of this ancient outboard.
As i was taking the motor apart i took lots of photos for reasembly purposes. I also found an exploaded view in the repair manual. The old one was cracked so i got a new one. The square O ring is inside the carbon seal with the sholder side facing the berring. The berring is flush with the bottom of the crank case. The side facing out has 2 small cut outs on the inner circumference, exposing a small part of the O ring. Then the large spring retaining washer then the spring then the small spring retaining washer then the snap ring to hold it all togeather.
What i dont understand is how this seal is supposed to hold any real crank case pressure in. It looks and functions alot like a 1 way valve letting pressure out.
How much pressure is it intended to hold?

 

[42 Clyde]

Yes i agree. 90 seems low but i have new rings and a fresh hone on the cylinder and all new gaskets. If i screwed something up during the overhaul than i did an equaly bad job on both cylinders becouse they are both exacly the same pressure. If anyone has any ideas or knowledge to bestow i will be happy to hear it.

 

[42 Clyde]

[No message]

 

[racerone]

It is such a simple seal.------The carbon rotates against the bearing and the spring holds it there.----The o-ring inside seals as well.-----No it it is not a check valve !----It is a magic well thought out " mechanical seal ".------Worked on similar seals that will hold 1000 PSI pressure.-----Brilliant stuff that !

 

[F_R]

Normal crankcase pressure runs around 4-.5psi

Does the lower cylinder have spark while it is running?

 

[42 Clyde]

It is such a simple seal.------The carbon rotates against the bearing and the spring holds it there.----The o-ring inside seals as well.-----No it it is not a check valve !----It is a magic well thought out " mechanical seal ".------Worked on similar seals that will hold 1000 PSI pressure.-----Brilliant stuff that !

Well i just put about 4 psi against it and it just blew by.
How does the quadrant O ring seal work if the carbon seal is only touching the berring on the flat face. Incidently thats where the air is escaping.
Does this look correct?

 

[42 Clyde]

Normal crankcase pressure runs around 4-.5psi

Does the lower cylinder have spark while it is running?

Yes. Both have spark. Hot and on time! Lol.
I have evin swaped all the parts side to side one at a time to see if any thing changes. Coils, condenser, points, plugs, reed valves, you name it ive removed it, tested it and probly started a thred on a forum about it!

 

[racerone]

The carbon if installed correctly seals across the face of the bearing.----The quad ring seals between the shaft and the carbon.----Something is wrong with that seal or the installation.----Post picture of the seal face on the carbon that contacts the bearing.----Show the bearing surface that contacts the carbon seal face.

 

[42 Clyde]

Done and done