Special needs guy needs johnson help

[CKMATE225]

My next door neighbor has some special needs and is very stressed right now so I am hoping one of the white motor guys can help,
He's got a older Johnson 25 hp 2 cylinder single carb (Late 80's early 90s)that will not make power. it idles Ok and seems to be running alright but he just can't get the boat to plain off, I checked the prop and fuel both fine. It was fine one day the next day he took it out and it just wouldnt make full power. I don't have a manual avalible but if someone can point me in the a direction to try to help him out I would appreciate it. This boat is the only thing that gives him a little independence . Thanks in advance.

[Forkin' Crazy]

I always start with a compressioin and spark check and go from there. Could be a coil, loose ground, bad pack, etc.

[Ray Neudecker]

First check compression and fire.

[demag67]

check the three major things, compression, spark, and fuel. make sure your compression is good on both cylinders, check that the timing arm is moving and that the timing is moving when increasing the throttle, put a spark checker inline and make sure it has hot enough spark, pull the carb, plow out the jets make sure that is clean, make sure you have good fuel flow to the carb (vent on tank is not closed, inline filter dirty, ball is not sucking down. could be something very stupid, i had a johnson 25 hp, had the same problem, but mine ended up being two things, someone took the cotterpin out of the timing advance rod which i over looked a million times, and i didn't know there was a screen in the fitting to the carb. good luck

[Riverman]

Has it been sitting? One of the main jets could be partially or fully plugged with gunk from bad or old fuel.

[CKMATE225]

Thanks for the replys, I have checked the timing advance its Ok I will check spark and fuel flow.
One thing I did notice when I checked it yasterday, it was really humid out and there was a milky ring inside the trought of the carb, I chalked it up to cold gas causing condenstion but am I missing something else here? I have used two different tanks to rule out water in the gas. and I have a sample set aside now to see if anything settles out, any ideas on that one?

[mrv8outboard]

Once you confirm that the motor has good compression and spark move on to the next issue. The main fuel circuit in the carburetor sounds restricted and or the idle mixture is set to lean. If when in the water the motor idles smooth as silk it is to lean. This can all be corrected with a simple but complete rebuild of the carburetor.

[CKMATE225]

Problem solved!, It appears that my special buddy next door didn't believe me the first time I told him he had water in his old gas tank 2 months ago. So last week he kept switching it back and forth between a good tank and a contaminated one, So I was going crazy testing everything and finding nothing wrong,It would run ok for a short time then crappy again, Tested everything again, Once again, nothing abnormal. I guess the milky crap in the carb throught was water from the gas. But, because I thought it was new fuel I figuerd it was some crazy atmospheric condition( humidity/cold fuel) But through all the BS he finaly ran the contaminated fuel out so I drained his carb bowl for hopefully the last time and flushed it with a fresh mix and he was off and running,(on a brand new tank). He was very proud of himself for figuring this all out on his own. (it only cost me 3 days and a new 6 gal tank. But he did it all on his "own" HA!!)
Thanks for all the replys, It makes for a tough problem when you have someone unintentionally sabatoging you while you are trying to help them out. But its all good now.