'93 Merc 175 hp, 90 psi compression on one side, 110 psi on other side

[gregBR549]

I am looking at buying a 175 hp Merc, I think it is a '93 or '94. I was checking the compression. On the left bank of cylinders (looking from behind) all 3 pressures were right at 90 psi. The other side had 110 on the top one, 110 on the middle one, and about 115 on the bottom one. I just spun the motor about 5 seconds on each cylinder with all the other spark plugs in. I had jumper cables hooked to the battery so I know it was spinning at normal starting rpm. Are those 90s too low? Is this due to one side getting hot? What are the chances I could get away with just new rings and a good honing? If I do have to do a rebuild with new pistions, rings, bore job, etc, how much would it cost if I did it myself?
thanks

 

[Dukedog]

Re: '93 Merc 175 hp, 90 psi compression on one side, 110 psi on other side

Try it again. Good "hot" battery. All tha plugs out. If you use the key you need to ground the plug wires. Best to use remote starter button with the ign. off. Crank it till your satisfied it as high as its gonna get. Make sure your guage is KNOWN to be good. Some arn't the most dependable with what they read........

 

[sschefer]

Re: '93 Merc 175 hp, 90 psi compression on one side, 110 psi on other side

With just the results of your compression test it's hard to tell if there is damage or just normal wear and tear. I would do a leak down test. That will help fill in the blanks about the engines general condition.

If you shop around and reuse as much as possible you can probably rebuild it for around 1000.00 - 1500.00. That's assuming that a lot of the parts are still within factory spec's and you are only replacing what is absolutely necessary. I may be a little high on the actual numbers but I think if you build that into your budet you'll be fairly safe.

If the block needs boring you can count on around 80.00 a hole and that also means new pistons. Something that simple can put you over the cost of a better engine fast. That's what you really need to think over.

If you're doing it for fun great but if you're hoping to find a sweet engine with little or no hidden costs, I think I would steer clear.