Compression Ratings?

[Paulz01]

I am looking to buy a boat with a 1997 Johnson 175 on the back. It is the carbed version. I gave it a compression test and the numbers were

110 - 115
110 - 110
100 - 100

Are these readings good? I know that there is a 15psi gap and that kinda scares me. Is that really that big of a deal? Also, the owner doesnt know the amount of hours, how much would you say then engine has?

 

[mthieme]

Re: Compression Ratings?

Numbers are good.
If anyone hazards a guess at any number of hours on the motor going by compression readings and year alone, we need to kneel down and start some Gregorian chants. The previous owner couldn't give you any idea how often he used it?

 

[BigB9000]

Re: Compression Ratings?

Hows the paint on the powerhead?

Maybe that'll help guessing the hours used

 

[JerrfyLube]

Re: Compression Ratings?

Compression numbers look fine...should run good.

 

[tashasdaddy]

Re: Compression Ratings?

i would do a decarb on it, may even out the compression #, but there is nothing to be alarmed about. i perfer this method.
Decarb, take a can of seafoam put 3/4 of it in the gas tank, with only 1 gallon of premixed gas. put the rest in a spray bottle. start the engine, and let it come up to temperature. then remove plugs, and them some real good shot of seafoam into the cylinders, replace plugs, let sit 15 minutes. restart, and spray the rest of the seafoam into the carbs, so the the motor almost stalls, wait and repeat until the seafoam is gone.then take for a wide open spin. then put in new plugs, ad premixed gas to the tank, and take it for a wide open throttle spin. it is going to smoke like a house on fire, during this process.

afterwards compression.recheck

 

[Sandhammaren05]

Re: Compression Ratings?

Compression is low and pretty uneven but motor can be run.

I am looking to buy a boat with a 1997 Johnson 175 on the back. It is the carbed version. I gave it a compression test and the numbers were

110 - 115
110 - 110
100 - 100

Are these readings good? I know that there is a 15psi gap and that kinda scares me. Is that really that big of a deal? Also, the owner doesnt know the amount of hours, how much would you say then engine has?

 

[emdsapmgr]

Re: Compression Ratings?

Don't worry about the compression variance on your engine. In 1994, OMC redesigned the heads on the 60 degree loopers. They increased the size of the head combustion area on the bottom two cylinders (the bottom one on each head) to lower compression. They are supposed to be around 8-10 lbs less than the others. Your compression numbers looks fine. You can run some Bombardier Engine Tuner through it and it may help somewhat.

 

[Paulz01]

Re: Compression Ratings?

Thanks guys. That makes me feel better.

 

[jbjennings]

Re: Compression Ratings?

Don't worry about the compression variance on your engine. In 1994, OMC redesigned the heads on the 60 degree loopers. They increased the size of the head combustion area on the bottom two cylinders (the bottom one on each head) to lower compression. They are supposed to be around 8-10 lbs less than the others. Your compression numbers looks fine. You can run some Bombardier Engine Tuner through it and it may help somewhat.

Whaaaaaat?? I'm amazed at the knowledge on this board!!!
Wow!

 

[jrod1997]

Re: Compression Ratings?

can someone give the correct numbers, im looking for 1997 200 johnson compression specs
engine runs ok at 4000 rpms, then bogs down almost to a stall, then i cant get back over 3000 rpm's
i also notcied after pulling the boat ive got blackish fuel smelling fluid streaming out of the exhaust, wondering if this could be lack of compression
i got readings from 90 to 100


thanks!