Compression

[harvey5560]

What should the compression be on a 2006 Yamaha 50HP outboard?

Thanks

[harvey5560]

I should also add... This a 2 stroke outboard

Basically the issue is this,

Boat has been running great all season gettign 35 MPH at 5500 RPM. This past weekend I was only able to get 27 - 28 MPH at 5200 - 5300 RPM.
I suspected dirty carbs ( last years gas although stabilized and since drained).
I took the boat to a marine mechanic ( not yamaha) and he sais compression is 110, 110, 105. spark is good on all cylinders and new OEM plugs.
two of the three plugs looked normal, one was slightly fouled.

Mechanic is going to clean the carbs but says it may not fix the problem.

just wondering if I may have a larger problem on my hands.

Outboard idles great, start up with little efford

[99yam40]

Which plug was not normal looking?
If it was #3 then check to see if the fuel pump is leaking fuel into the #3 crankcase causing too rich of a mix

[harvey5560]

Its the top cylinder that is rich.. Not sure if that would be #1 or #3

[99yam40]

#1 on top
#3 on the bottom

Compression should be OK
Compression, spark, timing, and fuel pressure can be tested very easily.
maybe just a bad plug,wire,cap,or coil. But they can be tested also
The input and output voltages of the CDI can be also easy to test with the proper test equipment to be sure the ignition system is functioning properly to rule that out. Then you are left with fuel/air mix(carbs plugged or sucking air)

[harvey5560]

Thank you for the suggestions 99YAM40. I will ensure the mechanic checks those issues out.
Hopefully its something simple. Carbs will be cleaned, that much I know for sure.
I'm a little concerned as the mechainc said the compression is below specs and could indicate a scorched cylinder from running last years fuel (although stabilized)

[harvey5560]

I just got the call from the mechanic advising me that the outboard is ready for pickup. HE cleaned the carbs and said there was a little varnish in the them but overall not too bad.
Timing was accurate, fuel pressure good, spark good on all cylinders, compression 105, 110, 110.

He said the outboard is running great in the test tank.

I will be picking it up on Thursday and will test it out at WOT on the water. Hopefully the problem is resolved. I've read enough posts to know that just a little varnish can cause problems with these carbs.

[harvey5560]

Well I took the boat out for a test run today and its running better than it did the day I bought it. Turns out the little bit of varnish in the carbs was all it took to reduce the performance by 25 percent.

Thank you to all that replied. Your assistance and advice is very much appreciated.