What do I do now? 1955 25hp Johnson

[greatoutdoors]

So, I have done a carb kit, new plugs, new coils, cleaned and gapped points correctly, compression seems good. Ordered new points and condensers just so it's all new. Still can't get it to stay running. Will fire after about ten hard pulls, runs smoothly for about 5-10 seconds, then dies out. Fuel and air lines and tank are good, I use them on my other motor which runs perfectly. What is wrong? The high and low speed needles seem worn and loose. Will this cause this problem? If so where can I find them? I'm getting gas in the carb bowl, so I'm stumped at this point. Does this motor have timing? How do I adjust it correctly if it does? Please help and thank you in advance.

 

[tashasdaddy]

Re: What do I do now? 1955 25hp Johnson

did you replace the packing in the carb needles, 2 seals per needle?

compression seems good, this tells us nothing. see compression test here >>
http://forums.iboats.com/showthread.php?t=299680

 

[greatoutdoors]

Re: What do I do now? 1955 25hp Johnson

Compression is 118 and 120. Ok, so I disconnected the vaccuum cut out switch wire and gave it a couple pulls and it fired and it ran well for about 30 seconds until i realized it wasn't pumping water, so i shut it off. it was pumping water for the few seconds I was able to get it to run previously. Why would this happen? Is it possible that the impeller just gave out because this was probably the longest it has run in a few years? Any input is appreciated. Thanks.

 

[greatoutdoors]

Re: What do I do now? 1955 25hp Johnson

Anyone?

 

[tx1961whaler]

Re: What do I do now? 1955 25hp Johnson

Could be. If you're running it in a barrel, the water level must be pretty high up the leg. Fill it up all the way and try again.
The impeller needs replaced anyway, if you don't know how old it is....

 

[greatoutdoors]

Re: What do I do now? 1955 25hp Johnson

Ok, great, I filled the barrell up a little more and it is pumping water great now. I splashed some out when I first got it running and put it in gear. Does anyone know why it will only run when the vaccuum cut out switch is disconnected?

 

[tx1961whaler]

Re: What do I do now? 1955 25hp Johnson

It's probably is a bad switch. Check it when it's not running to make sure it's not shorted to ground. It should never be grounded, unless the engine is over-revving.

 

[greatoutdoors]

Re: What do I do now? 1955 25hp Johnson

It's probably is a bad switch. Check it when it's not running to make sure it's not shorted to ground. It should never be grounded, unless the engine is over-revving.

Is it ok to just leave it disconnected or completely remove the wire? Isn't that mechanism just there to stop the motor from over revving? What could make that happen anyway?

 

[jbjennings]

Re: What do I do now? 1955 25hp Johnson

Yes, you can take the wire completely off and run it with no cut-out switch. However, they put it there for a reason. If you ever hit something underwater and kick the motor up and the prop looses any bite on the water, your motor may have a runaway and if a rod comes loose, I wouldn't want to be anywhere near it. Also, if your clutch dog slips and doesn't catch again, same thing. I'm sure there are other common scenarios where you'd wish you had that cut-out switch on your motor. I'd place a free ad on aomci.org and get myself one. I've had my favorite fastwin hit an object and I wish I had a cut-out switch on it. Luckily, no damage occurred other than a broken flywheel key.
Nice motor,
JBJ

 

[tx1961whaler]

Re: What do I do now? 1955 25hp Johnson

The usual way to happen is to rev the motor up too much in neutral or while running it in a barrel. The motor then goes into something called "thermal runaway", where it revs to the max, and you can't shut it off unless you choke the motor out. Even pulling the spark plug wires off won't stop it.
It can also happen if the prop drive pin shears off when running.
It is a useful item to have on the motor, and there's not much to them to fix:

 

[greatoutdoors]

Re: What do I do now? 1955 25hp Johnson

Thanks guys, great answers, great forum!