1972 Johnson 25 HP

[browning84]

This is my first post. My name is Nathaniel and I am new to the boating world as of early this year. Went from no boat to 2 boats and 1 motor in 6 months. Rehabed the first one and just got rid of it. I look forward to being here and learning the ways of boats.

I have a 1972 Johnson 25 HP 25R72R that I came on a boat I bought earlier this year. The guy said it ran the year prior but wasn't running after some maintenance he did on it before I bought it. This is my first outboard and I'm not what you would call a small engine mechanic (I prefer larger engines). I sent a pm to Jim to get the manual in hopes that the carb settings will be in there. I unscrewed the fuel mixture adjustment to check the needle and it is clean as a whistle. I know that is not a determining factor on how clean the carb is but it leads me to believe it is fairly clean. This is a pull start motor and about the only way I have been able to get it to fire is at about 1/2 to 3/4 throttle with the choke closed and at that it only occasionally fires. When it fires I can't really keep it going unless I feed it more throttle but it eventually dies. This leads me to believe it might be carb settings and it needs to be dialed in but I don't know where to start on that. New mixed gas in the tank. I am looking for thoughts and pointers on where the problem may be.

 

[Johnny]

many posts like this in the past.....
most everyone comes to the consensus of fuel starvation.
start checking the fuel flow from the gas tank, through the hose,
through the squeeze bulb, check all clamps for tightness, O-rings
in the fittings, then, the fuel pump itself.....
if all that passes inspection, you may have to disassemble the carb
to check the float level, etc etc etc
one small thing could be a big problem.
Timing could also be an issue, but that is totally out of my realm.

my '79 25hp Johnson had bad O-rings, loose clamps, squeeze bulb, fuel pump.
anything fuel related, I replaced completely. then a carb gasket kit - now runs great.

good luck !!

 

[browning84]

Good news and bad news. I got my service manual in my email this morning and the needle valve was WAY to far out, it's amazing it ever started to begin with. Now she starts and stays running but needs some fine tuning. The bad news is I can't do the fine tuning because when I got her to run long enough to actually look and see if she pumps water there is none coming out of the exhaust. I may also have a fuel pump issue, but I am looking for thoughts on this. A couple times it cranked and then shut off fairly quickly I went to go crank it again when it should have cranked right back up and I checked the bulb and it had lost fuel pressure. Is that something between the tank and the pump or is it the pump itself???

 

[Johnny]

starting with the Fuel Line - double check all the connections - then the squeeze bulb.
use something that will not damage the O-Ring seals .... like a Q-Tip or something
in both ends at the same time to drain the line... .

DO NOT USE SHARP THINGS TO OPEN THE BALL BEARING SEALS !!!!
yeah yeah yeah I know, same thing as putting a bobby pin in your ear !! LOL

The squeeze/primer bulb has only ONE moving part inside of it. There is a nylon
"cage" that holds a plastic ball. This sets up a "one way flow" of fuel. The plastic
ball must seat cleanly into its seat to prevent backflow and air leakage. Any small
piece of trash can disrupt the siphon and pressure design.
Contrary to popular belief, there is no spring inside the bulb, only this free floating
plastic ball. The primer bulb works best if it can stay in the vertical position with
the arrows pointing upwards.
Also, inside the bulb, there is a plastic bladder that holds the fuel. The fuel itself never
comes in contact with the outside black rubber bulb. If the bladder has a hole in it,
it will not function properly, thus, giving you fuel flow problems.
Then, do the rest of your fuel flow checks, clamps, fittings, fuel pump, etc.