25 hp johnson problem!

[stevenb32]

Hey guys i am having a problem.I have a 1970 25hp johnson motor,it cranks and runs at low speeds of about 5-10mph,but when i go to open it up it bogs down and goes dead.I can crank it back up and run low speed but it wont go any faster.Can anyone enlighten me on what the problem could be?Thanks in advance.

 

[racerone]

Start with a compression test.------Follow that with a spark check, both leads must fire accross a 1/4" gap.

 

[stevenb32]

how do you do a compression test?This is my first boat i have owned and i know little about them.i have had ppl tell me its nothing major but they r not experts on them or anything.

 

[F_R]

You do a compression test with a compression tester. We all have learned the hard way to do that first to evaluate the general condition of the motor. Having said that, since your motor starts and idles well, the compression is more than likely OK. I think you have a dirty high speed jet (orifice plug) in the carburetor. It is in the very bottom of the carburetor, deep behind the hex drain plug. It a precision part and must be absolutely CLEAN! You need a special screwdriver to get it out without damage.

 

[stevenb32]

Ok my dad said it sounded like a jet but he wasn't sure I will try it and let you know thanks

 

[Chavi]

I agree with F_R and think that it is probably a clogged jet. As for the compression test, what I have done in the past to test the compression on a 2000's model Mercury was I went to Autozone to take advantage of their Loan a Tool program to borrow the compression gauges. It comes with several sized spark plug type of tools that hook up to where the plugs are located. You turn the engine and the gauge will tell you what compression the cylinder has. It is said that each cylinder is supposed to have the same amount of compression (give or take 3-5 lbs).


Good luck, hopes this helps.
Chavi

 

[bonz_d]

Also to add, on an engine that old and being new to you I would suggest changing all the fuel lines inside the engine. As you have no ideas as to their age or condition. The old lines that were used are not resistant to ethanol and deteriorate quickly which can and will foul a carb.

 

[stevenb32]

ok I took the carb off and cleaned it and blew air through the ports.There was a bunch of white stuff in the main,but I got it back together and hooked it up now the motor wont crank.It acts like it is flooding out.I put it in a barrel full of water and the primer bulb doesn't seem like its getting primed all the way.the motor cranked for about two seconds and then went back dead.also is there suppose to be a lot of oil and gas coming out in the barrel of water.I would take it to someone to get it worked on but no one does it in my area.If anyone knows what could be going on I woul greatly appreciate it.Thanks in advance.

 

[nphilbro]

Of you've got someone to lend a hand, you could disconnect the the line from the fuel pump to the carb and have them block the outflow of the fuel pump while you prime it. This is just to confirm the leak is in the carb (since you just rebuilt it). It's been a while since I've pulled one of those apart, but I think if the float in the bowl is stuck it will cause fuel to just flow out of the carb. Others will chime in, I'm sure.

 

[racerone]

Maybe the fuel pump has a hole in the diaphragm, easy fix for that.

 

[steelespike]

I would suspect you didn't get the float or float valve together right.
When you squeeze the primer bulb it fills the carb float bowl, when full the the float valve closes and the bulb gets hard.
If it doesn't get hard fuel is likely flooding the motor.

 

[stevenb32]

ok thanks I can hear the gas trying to go into the fuel pump when I pump the bulb it sounds like a sucking noise.But the bulb does notget hard.I checked the float on the carb and put everything back the way it was but I could've not tightened everything all the way.is there suppose to be a spring on the pin for the float,mine just has a pin through the hinge but no spring and the needle is under the float.I looked at the carb kit and it had one in the kit but mine didn't have one on it when I took it off.

 

[racerone]

There is a " clip " in many carburetor kits.---The purpose of that clip is to pull the needle off the seat when the float drops as fuel is used.

 

[newhamburgboating]

Of you've got someone to lend a hand, you could disconnect the the line from the fuel pump to the carb and have them block the outflow of the fuel pump while you prime it. This is just to confirm the leak is in the carb (since you just rebuilt it). It's been a while since I've pulled one of those apart, but I think if the float in the bowl is stuck it will cause fuel to just flow out of the carb. Others will chime in, I'm sure.

Can confirm, Looks like niagara falls

 

[stevenb32]

The float was upside down don'tknow how I done that

 

[stevenb32]

Ok I got the motor running right I ordered a carb kit from here and it was the needle and clip. The carb wasn't getting enough gas to open up. But I have another question how fast should this motor push a 14 ft extra wide extra deep boat it doesn't feel like it's going as fast as it should be but I don't know bc I've never had one. Thanks for all of yalls suggestions yall helped out a lot.

 

[ultra353]

I had a 67" beam 14ft aluminum with a '69 Johnson 20 hp that would push it about 25 mph