1975 Johnson 25 hp carb help

This was a outboard my grandfather had and it has not been run in probably 8 years or so. I changed the lower unit oil, plugs, etc hoping that the last person who used it ran it out of gas. It would not start so I got a service manual for it and I broke down the carb tonight. You can see in the pics what I found. White chaulky powder which I assume is whats left of the fuel that was trapped in the carb for the better part of a decade.

My plan is to blow it out with compressed air and the soak it in carb cleaner. Then buy one of the carb rebuild kits and change out all the gaskets, etc. Am i on the right track here? First time tinkering with an outboard.

Can't hurt. Good luck.

Yep, I say a carb rebuild is a good start. Also, check the fuel hoses and water pump impeller.

Thanks, I am going to order the carb kit and an impeller and go from there.

I have had that same carb on my 25 easy rebuild and it sure made a difference in the performance of the engine. I did not mess with the float setting at all because it was more a jet issue with mine. It did have a starting issue and idle issue. Both fixed with the carb kit.

Need some help. I rebuilt the carb as recommended above and I just got through replacing the impeller. In the service manual it says after putting in the new impeller, you turn the driveshaft clockwise to position the impeller in the correct direction inside of the impeller housing. after doing this I could still turn the driveshaft by hand. After I screwed down the 3 screws on the impeller housing (see pic) I can not turn the driveshaft. (by hand or with a pair of channel locks) Is this correct? or should it still turn once I tighten down?

It also says tighten to "specified torque" but it doesn't say what that is. But even if I barely tighten, I can't turn driveshaft. if I loosen back up, I can turn.

I use petroleum jelly on the impeller when I first install a new one. Maybe it's just too dry?

Another thing I found out was to turn the drive shaft with an electric drill, but make sure it's turning in the clockwise direction as looking down from the top. This also helps to prove if pump is moving water by placing the lower unit in some water before installing to the motor.

Good luck.

I tried the jelly. It still is difficult to turn, maybe a little better. So i put some locktite on the threads and only tightend them to the point where the impeller will still turn. Hopefully that is correct, ha ha. I don't want that thing coming apart when I am running it.

jonmac3569 said:

I tried the jelly. It still is difficult to turn, maybe a little better. So i put some locktite on the threads and only tightend them to the point where the impeller will still turn. Hopefully that is correct, ha ha. I don't want that thing coming apart when I am running it.

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I calibrate my elbow for small bolts and nuts! I hope you used the Locktite that can be loosened when you need to. I once used that "permanent" Locktite on a bicycle rack on a car and it went with the car when I traded it in. :shock:

hopefully you bought omc rebuild kit.the sierra and other aftermarket kits break down from the ethanol.bought 2 kits within a month and a half.then bought omc havent had a problem.

Yeah, it is supposed to be the locktite that you can remove if needed. That would be bad, ha ha

Yeah, not OMC. It says "gilmarine" and has a part number of 40560, replaces the original part number. Not sure what it is but hopefully it will hold up.

Reattached the lower unit back to the motor, now if i put the motor in neutral i can only get about a 1/2 pull on the starter rope each time i pull. used to be much smoother. I think it has to be related to the impeller housing issue i had above. The only thing i know to do is loosen up the impeller housing screws to where it will spin easier but it already seems that it is not tightened down enough. I basically hand tightened the screws and added locktite so they wouldnt back out on their on. any ideas?

Actually, now that I think about it, those screws are probably a couple full turns past hand tight. But about three full turns (at least) from being turned all the way down. Should I try backing them out some and using the locktite again? It will definately spin easier if that impeller housing is not crushing the impeller. Just doesn't seem right having it designed to where the screws only turn down halfway. Seems like you should be able to tighten it down and the impeller would still be able to spin.

Did you try and install the impeller inside of the housing first just to see if it fits correctly? Maybe the impeller is too tall and being squished inside of the housing?

My second impeller kit for my Johnson had the wrong impeller. It wouldn't fit over the key.

Good luck.

ok this is maybe the problem,this is from a omc service manual.coat impellar cup with oil and with a COUNTERCLOCKWISE rotation,install impellar into cup...make sure impellar is correct one,make sure it is the same as the other one you took off.if u hv any question pm me.

larryg said:

ok this is maybe the problem,this is from a omc service manual.coat impellar cup with oil and with a COUNTERCLOCKWISE rotation,install impellar into cup...make sure impellar is correct one,make sure it is the same as the other one you took off.if u hv any question pm me.

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I believe it's counterclockwise if you're looking up from the bottom which would make it clockwise looking down from the flywheel. :shock:

Ok, I will have to check that out. I turned it clockwise if you were looking down from the flywheel. I just held the lower unit with the crankshaft pointing toward the ceiling, and turned it clockwise.

I think I will take it back apart and just make sure the impellers are exactly the same. I compared them before I changed it out but I didnt check the exact thickness.

From what my manual says (see pics below) I think I have the impeller turned the correct way. First chance I get I am going to take it back apart and just make sure it is exactly the same as the old impeller.