1996 Force 120 with crazy compression numbers

[Kidsoncoffee]

I just bought a boat with a 1996 Force 120 outboard that's been sitting for over 10 years. Previous owner knows nothing about its condition. I finally got it home and bought a new starter for it. I've ran a compression check with 2 different compression testers and the numbers are kinda freaking me out.
#1 cylinder 155psi
#2 cylinder 175psi
#3 cylinder 165psi
#4 cylinder 175psi

Can anyone chime in as to why on earth these pressures are so high? As of now I'm soaking the cylinders with marvel mystery oil as I can only assume it's stuck rings, corrosion, and carbon making the numbers so high. I'm at the point where I don't know if I want to put money into this engine or just repower with a used motor. Anyone else seen numbers like this on a force? I know the 10% rule, but the high pressures are giving me some serious worries. Any help or guidance is appreciated.

 

[Faztbullet]

Dont know why people add oil to cylinders as it can cover up compression issues. If been setting as posted a quick shot of WD40 in cylinder and carb intake is all it needed. Compression would be low if rings stuck, 120-130+psi is good on a crossflow motor. If concerned get a bore scope or pull head and inspect cylinder walls

 

[Kidsoncoffee]

Dont know why people add oil to cylinders as it can cover up compression issues. If been setting as posted a quick shot of WD40 in cylinder and carb intake is all it needed. Compression would be low if rings stuck, 120-130+psi is good on a crossflow motor. If concerned get a bore scope or pull head and inspect cylinder walls

Is 175psi OK to run? I've never seen compression that high on a 2 stroke outboard this size. I'm just racking my brain trying to figure out why the pressure is that high.

 

[Sea Rider]

What compression numbers does the motor manufacturer calls for ? With motor sitting fully horizontal squirt several shots of CRC decarbononizer inside each cylinder, let soak for some hours, re test compression numbers.

Happy Boating

 

[Faztbullet]

Could be the added oil....

 

[racerone]

Remove bypass covers and have a look for condition of pistons / rings.----All easy to do.

 

[Kidsoncoffee]

Thanks for all the replies. For about $250 I can get the engine running. It needs a new stator, trigger, carb and fuel pump kits, and thermostat. I guess I'm gonna chance it and see what she does. Maybe the pressures will settle down some. It's a saltwater engine so I don't wanna take off the head just yet. Too many broken bolts to deal with if I go that route. I initially pickled the cylinders with marvel as a precautionary measure. Didn't want to try and turn it over and cause more damage than needed. I'll update in a month or so once I get all the parts in and get er running. Again, thanks for the replies.

 

[roscoe]

FYI, I had 145-150# in my '95 Force.
And 148-160# in my 1997 Force.

 

[Nordin]

Those number do not sounds so weird.
OEM factory service manual through 1991 A models call for 145-165 PSI for the 120Hp.
It can be the gauges that shows incorrect values, but in my opinion it is pretty normal.
I have two Chrysler 45Hp "super sport" that was ligthly "hotted" from factory with a TC carb and they have almost 195 PSI in both cylinders.

 

[Scott Danforth]

I finally got it home and bought a new starter for it. I've ran a compression check with 2 different compression testers and the numbers are kinda freaking me out.
#1 cylinder 155psi
#2 cylinder 175psi
#3 cylinder 165psi
#4 cylinder 175psi

quality compression testers....... or two walmart specials?

 

[Kidsoncoffee]

quality compression testers....... or two walmart specials?

1 snap on and 1 napa tool brand. Both read within 3 psi of eachother.

 

[Kidsoncoffee]

Those number do not sounds so weird.
OEM factory service manual through 1991 A models call for 145-165 PSI for the 120Hp.
It can be the gauges that shows incorrect values, but in my opinion it is pretty normal.
I have two Chrysler 45Hp "super sport" that was ligthly "hotted" from factory with a TC carb and they have almost 195 PSI in both cylinders.

This eases my mind. From all the reading I was doing, 150ish was max anyone was seeing from these motors. I'm gonna go ahead and spend the money to get it running. Pulled the thermostat and not much corrosion at all for a saltwater motor, so I think it's worth investing in.

 

[puffitu]

I say dive into it. I’ve resurrected a 88’ 125hp with parts from 90’ 120hp and it runs like it was new. I’ve got parts of you need-good luck

 

[jerryjerry05]

The factory doesn't really post the comp #s as they can vary so much.
The later models were actually designed with the top/bottom cyl. comp lower than the two middle ones.
The #s I remember are 155 #1/4 165 #2/3
I've seen the results as high as 175-180 on a 94 120
You sure it needs all those parts?

 

[Kidsoncoffee]

The factory doesn't really post the comp #s as they can vary so much.
The later models were actually designed with the top/bottom cyl. comp lower than the two middle ones.
The #s I remember are 155 #1/4 165 #2/3
I've seen the results as high as 175-180 on a 94 120
You sure it needs all those parts?

Thanks for the info. And yeah it needed the parts. The wires on stator and trigger were crumbling to the touch and I ran a resistance test and both were shot. Working on getting the console wiring sorted out and some new power and ground blocks installed. Hopefully I'll be ready to try to fire her up in the next couple of weeks. Haven't assessed the fuel tank yet though I did buy an endoscope to inspect the tank with. Will be testing with an external tank until I can drain and test the internal tank. I'll update once it's running and post compression numbers once I've gotten a few hours on the hose with it. Holding off on buying new control cables and steering cable until I can fire the motor. Wiring is a literal rats nest. I filled my 8 gallon shop vac from all the rats nesting and pine needles throughout the console and rear compartments. Hoping the critters didn't chew through the wiring in the tunnel from the motor to the console. Going to be doing a ton of ground checks on that mess.