Compression on 99 Merc Jet 20

[LuckyFish]

Have compression readings of 85 in one cylinder and 65 in the other on my 99 Merc 20 Jet (25hp).<br />Info was supplied by dealer. What is normal on this motor? ser # OG766818

 

[Yepblaze]

Re: Compression on 99 Merc Jet 20

Those sound like low, or very low readings BUT......<br /><br />I've seen plenty of variance between guages, so without a second opinion from another reputable guage I'd reseve a condemnation as of yet. <br /><br />What's normal you ask?<br /><br />Usually around or over 100 within 10-15% of each other.<br /><br />Did it still idle and run ok?

 

[LuckyFish]

Re: Compression on 99 Merc Jet 20

Yes on the idle, but no power on top end.<br />Thanks for the reply

 

[Yepblaze]

Re: Compression on 99 Merc Jet 20

If you have ever experienced the motor to have top end power different than what I explain below, then I'm wrong but,.....<br /><br />No apparent power on top end is what that motor would be expected to do. <br /><br />Wide open making a racket and going nowhere.<br /><br />Getting a jet to hook up and push a boat is tough.<br /><br />Sorry but jets are somewhat like that. Especially one that small.

 

[LuckyFish]

Re: Compression on 99 Merc Jet 20

Ok then, Time to upgrade I believe. You answered my question in the first post anyway. Thanks<br />Lucky