1994 Mercury 90 HP 2 stroke

[Carpcatcher]

Can anyone tell me the compression spec's on a 1994 Mercury 90hp 2 stroke motor???

 

[racerone]

Post your numbers !

 

[Texasmark]

Can anyone tell me the compression spec's on a 1994 Mercury 90hp 2 stroke motor???

Yeah! Per the manual: "if compression is less than 120 expect problems".

 

[Carpcatcher]

Post your numbers !

I just checked the compression, after running the motor in water for about 30 minutes to warm it up to operating temp. #1 was 100psi, #2 was 95psi, #3 was 95psi.

 

[racerone]

If gauge is a good one I would take off the exhaust cover to have a look at the pistons rings.----Perhaps test with another gauge first.

 

[Carpcatcher]

If gauge is a good one I would take off the exhaust cover to have a look at the pistons rings.----Perhaps test with another gauge first.

Thanks for the response "racerone", we bought the boat last week, '97 Sun Tracker 21', the people said they didn't use it much and had been sitting since last Oct. We have not had it out yet to see how it will perform on the water. I'm hoping it will do OK. The idle is a little rough when we run it in a bucket. I don't want to open up the inside of the motor until I see how it runs on the water.

 

[racerone]

Good luck with it.

 

[Carpcatcher]

Good luck with it.

Thank you sir.

 

[wn6ngp]

I think you will have good luck with it. Just don't wander too far from the dock or ramp the first time out. If it doesn't run well first time don't be alarmed as earmuffs and buckets aren't always a good indicator. You may need to clean the carbs.

 

[Texasmark]

Thanks for the response "racerone", we bought the boat last week, '97 Sun Tracker 21', the people said they didn't use it much and had been sitting since last Oct. We have not had it out yet to see how it will perform on the water. I'm hoping it will do OK. The idle is a little rough when we run it in a bucket. I don't want to open up the inside of the motor until I see how it runs on the water.

Tell you what, before you start tearing things apart and maybe spending a lot of time and money that isn't necessary: Go to a www search engine and "Google" (for one) the word DeCarb. You'll notice references to iboats in your answers. Pull it up and follow the instructions. Sea Foam is available everywhere; not a problem to find....white with red label, 16 oz can. After that and running some SF in your fuel for several hours then decide if you need to rip things apart.

 

[racerone]

I would not consider ----" removing " the exhaust cover to be " opening up the motor "----It allows you to inspect the pistons / rings.----Will cost you the gaskets.-----Can't afford gasket then ?

 

[Carpcatcher]

Yeah! Per the manual: "if compression is less than 120 expect problems".

Update since last post.....almost 2 months past. Turns out the compression gauge was reading about 40 pounds low so we can throw out the compression test results. The truth is out on the water anyway [ if you don't have a good compression tester]. I ran the motor several more times in the bucket with fresh gas. The more I ran it the better the idle got. We took it out on the river today and ran it for about 3 hours. The idle is still rough but from 2000 rpm up it's all good. We ran it up and down the rpm range from 1500 up to 6000 and the motor performed well.
Next step is to get some of the Sea Foam, have fun on the water, be safe,and catch some fish!!! Thanks again for your input and advise! Safe Boating...........