CD17 5.5Hp Compression question

[austin]

I picked up this 5.5 hp motor. Before I put any money into getting it running, I checked the compression.
I’m getting 62 on the upper and 72 on the lower cylinder.
Is this good enough pressure, and what does it mean when the pressure are not equal?

Thank you for any help!

[chris-p]

It is on the low side of what I would like to see. DIfferent gauges read differently though, method of testing, etc… How did you test?

Rings could be stuck, bore worn, damage to piston and/or cylinder wall, faulty head gasket, warped head, to name a few.

[austin]

I used 2 different gauges, both were within 1 lbs of each other.
With a scope, I couldn’t see damage to the cylinders.
Should I pull the head?

[crosbyman]

are you a betting man ? … what is the asking price. I paid 50$ for a real nice 9.5. great engine after 3-4 weeks of soaking

Joining AOMCI has priviledges 🙂

[lindy46]

Set with cylinders pointing up, and spray some penetrating oil in. Let it set a few days and see what happens before pulling the head.

[chris-p]

If it runs, the best way to unstick the rings is with OMC Engine Tuner, or seafaom.

Both work very well.

I mix a heavy dose with the pre mixed fuel, about a gallons worth.

Then I put the rest in a spray bottle. Run the motor at a fast idle, and pump the seafoam into the carb throat. She will smoke like its on fire! Empty the solution into the carb, then let it die. Let it sit overnight, to break up the carbon. Then in morning, take for high speed run. May need to change plugs after. I have increased compression dramatically this way, if the rings are stuck. Its not magic though, wont fix damaged piston, damaged cylinder, etc…

[austin]

I have had it running, but gas comes out of the carb, so I pulled the carb and was going to order a carb kit after I figured out everything else I may need. Then when I checked the compression, I figured I better find out whats going on before I get to much into it.
I have seafaom, would it be ok to let that sit in the cylinders as lindy46 suggested?

[austin]

quote crosbyman:

are you a betting man ? … what is the asking price. I paid 50$ for a real nice 9.5. great engine after 3-4 weeks of soaking

I paid $50 for this little motor, figured if just for parts it was worth that. I really would like to see it run again!

[Doug Wilson]

i have a cd16 that was in the 65 to 70 range last i checkecd it but had been setting 15 years or so runs real good now have not checked it since i rebuilt the lower unit and ran it about 8miles on the river .
Doug

Doug

how is it motors multiply when the garage lights get
turned off?

[fleetwin]

Yes, go ahead and try the seafoam/engne tuner…It’s OK to let is soak for a few days. But, keep in mind this stuff is not a lubricant and could promote rust if left in there too long. The engine should be run hard in gear at WOT throttle for a few minutes after the treatment to be sure all of that stuff is expelled from the engine.
If there is still a 10PSI difference afterwards, I guess I wouldn’t worry much if the engine starts and idles reasonably well. I wouldn’t pull the head unless the engine doesn’t run well after the treatment. Keep in mind that there are many other causes of poor running besides uneven compression.
Should have mentioned this first. Be sure to mix the fuel/oil at 16:1 for this engine, the rods just have plain bushings that need the extra lubrication.

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