1998 15 hp Evinrude won't idle

It won't stay running below 1100 rpms. I have had the carb cleaned (ultrasonic) and still no improvement. I have taken the carb from my buddies perfect running 1997 15hp Johnson and installed it, still the same. I have set the cam roller at the mark on the cam, a little in front, a little behind, still the same. It sounds like it is bogging down. It also sounds like it is getting too much air. I checked the compression 100psi in both cylinders. I talked to a marina and was told that the compression is too low and that is why it won't idle. Reading other forums however, it seems this motor should still run fine even at 100psi. Also, new spark plugs. Is there a way to adjust/set the timing? Any help would be great.

Timing on this motor simply does not go out of adjustment unless the flywheel key shears for some reason.------------You might want to remove the exhaust cover to have a look at the pistons and rings.-----------Water pump been looked at?-------Possible issues with a reed valve ?

The motor runs fine at high speed. Would the reeds cause an issue with idling? Cause the bogging sound? The sucking too much air sound? The water pump and temp are fine. I checked the temp with a temp gun. If the motor is capabable of running fine with 100psi I would rather element everything before I start tearing into the guts of the motor.

Well, I guess some more trouble shooting is required.----Good luck with the project.

I think my last post was taken the wrong way. I don't know what to look for if I took the water jacket off. It has 100psi in both cylinders. I guess that tells me they have worn equally and if the compression isnt too low it should be able to run. It sounds like it is bogging down, sounds like it is sucking in too much air (sounds different than my buddies 1997 15hp johnson). Could the reed valves be to blame for these sounds and idle issues? After reading my last post it does seem desmisive. I am sorry, I didn't intend that.

If you have a reed problem you'll see a lot of spit back out of the carb at idle.

i can't get it to stay running below 1000rpm. Should I still see spit back? Maybe some ignition part is going out. I have my buddies 15hp johnson and I could swap parts out. I guess I still don't know if this motor should still run properly with only 100psi in both cylinders.

Have you looked for a wee hole / crack in the crankcase !!!!

I will look for any signs of a small hole in the crank case. Any tell tale signs of a cracked crank case? Also, would it still run fine at high rpms with a cracked crank case? Thanks for your help.