Johnson 3hp starts and dies after a couple of seconds

[Justin-KS]

I picked up a old Johnson 3hp(1954) as a project, and now Im stumped. So Ill start with what Ive done so far. When I got the motor the guy said it had sit for a couple of years. So with nothing to lose I put some fresh gas in her and pulled the rope a few times. I was able to start her at half way between start and fast and keep her running and rev her up without it dieing as long as I didn't throttle down. So I decided it was worth messing with.

Here is the list of things I did to her since I decieded it was worth messing with.
- Set the points, the coils look like they have been replaced. No cracked insulation and bright green in color, not faded at all.
- Checked spark, will jump a 1/4 inch gap with a loud audible snap.
- Ordered a new carb kit w/ a float, gave it a good cleaning, blew it out, and installed new kit. Set the high and low speed needles according to Joe Reeves write up.
-Cleaned tank and blew out the ceramic filter. When I open the valve the gas kinda dribbles out in a steady flow but not real fast.
- Installed a new impeller

So I got it all put back together, pulled the rope and nothing. Bumped up the throttle, she fired up for a few seconds and died. Tried again and same thing. Will run a few seconds then die like it is running out of gas. Im still getting gas, but is it to slow? Pulled the carb off again, blew it out, reinstalled, and still same thing. The float is level, and spring on needle valve is on. What can I check, or where do I go from here? Also if I wait 15 seconds after she dies, then 1 pull she will start and die the same way. If you try right after she dies won't start. Its like you have to wait for the bowl to slowly fill up.

 

[F_R]

Re: Johnson 3hp starts and dies after a couple of seconds

I picked up a old Johnson 3hp(1954) as a project, and now Im stumped. So Ill start with what Ive done so far. When I got the motor the guy said it had sit for a couple of years. So with nothing to lose I put some fresh gas in her and pulled the rope a few times. I was able to start her at half way between start and fast and keep her running and rev her up without it dieing as long as I didn't throttle down. So I decided it was worth messing with.

Here is the list of things I did to her since I decieded it was worth messing with.
- Set the points, the coils look like they have been replaced. No cracked insulation and bright green in color, not faded at all.
- Checked spark, will jump a 1/4 inch gap with a loud audible snap.
- Ordered a new carb kit w/ a float, gave it a good cleaning, blew it out, and installed new kit. Set the high and low speed needles according to Joe Reeves write up.
-Cleaned tank and blew out the ceramic filter. When I open the valve the gas kinda dribbles out in a steady flow but not real fast.
- Installed a new impeller

So I got it all put back together, pulled the rope and nothing. Bumped up the throttle, she fired up for a few seconds and died. Tried again and same thing. Will run a few seconds then die like it is running out of gas. Im still getting gas, but is it to slow? Pulled the carb off again, blew it out, reinstalled, and still same thing. The float is level, and spring on needle valve is on. What can I check, or where do I go from here? Also if I wait 15 seconds after she dies, then 1 pull she will start and die the same way. If you try right after she dies won't start. Its like you have to wait for the bowl to slowly fill up.

"Wait for the bowl to fill up" Well that's part of it for sure. That dribble don't get it. Those sintered filters are impossible to clean. You are supposed to just replace it. Personally, I remove the sintered part and solder in a brass screen. HOWEVER, it sounds like you have other problems as well. Once the bowl is full it should run 10-15 seconds, depending on how much you are using the choke, till it consumes the gas in the bowl.

 

[Justin-KS]

Re: Johnson 3hp starts and dies after a couple of seconds

Well I got the filter cut off and soldered a small screen in place. Put it all back togather and Im still at the same spot. What are a few things I could look into, or things to try? Also when I start it Im still having to bump up the throttle and not choking it. If I choke it, even if it is cold, it won't start. Could something be blocking the exshaust or could this be a reed problem? Should I still be focused on my carb?

Neither manipulating the choke or spraying premix into the carb does not keep the motor running any longer than normal.

Thanks for any input
Justin

 

[Rick.]

Re: Johnson 3hp starts and dies after a couple of seconds

You could try turning in the slow speed needle a little at a time. If you can't choke it it is probably getting too much fuel. Give it a try, say 1/4 turn in at a time. Rick.

 

[F_R]

Re: Johnson 3hp starts and dies after a couple of seconds

You could try turning in the slow speed needle a little at a time. If you can't choke it it is probably getting too much fuel. Give it a try, say 1/4 turn in at a time. Rick.

And your compression is...???? Does it show signs of previous overheating, other than the flat plate on the side? How far do you have the needles open? 3/4 on the lower and 1 1/2 on the upper should get it running. Exhausts and reeds normally don't give problems unless some vermins got in there.

 

[Justin-KS]

Re: Johnson 3hp starts and dies after a couple of seconds

My compression is low but even on both at 65 pounds, I figured it was fine since it started and stayed running before I started replacing things. I also thought that I could get my compression up with a decarb once it was running. I have messed with the slow speed changing it by 1/8 turns with the only difference being not able to start once it gets to far in. I set my LS at 1 turn out after seating and 1 turn out on my HS, but have adjusted both at multiple settings with no differences.

I'm I just wasting my time with the compression to being this low? Another thing is my compression gauge is older and is not a screw in type, it just has a rubber fitting you push against the spark plug hole.

Should I pull my head and look at the cylinder walls? Would spraying seafoam in the cylinders and letting it sit over night help any? If it has gotten overheated before could the head gasket be giving me problems? Would you replace the head gasket and surface the head, or should I tackle other things before trying this?

 

[tx1961whaler]

Re: Johnson 3hp starts and dies after a couple of seconds

It will run just fine at 65 psi. That is not your issue.

 

[Justin-KS]

Re: Johnson 3hp starts and dies after a couple of seconds

Well in the process of messing around with it I discovered something new and helpful I think. I shut the gas off and she instantly fired up and ran for 10 to 15 seconds before she died. I pulled the bowl off again and checked the float with the enclosed ruler and she is sitting perfectly level, but she flooding out (right).

So should I adjust float at a slight downward angle, or is there something else to look at/ for? I think all the gaskets in the carb are in the right place, and as stated before it has a new needle, seat, and float that came in the carb kit.

 

[tx1961whaler]

Re: Johnson 3hp starts and dies after a couple of seconds

Well in the process of messing around with it I discovered something new and helpful I think. I shut the gas off and she instantly fired up and ran for 10 to 15 seconds before she died. I pulled the bowl off again and checked the float with the enclosed ruler and she is sitting perfectly level, but she flooding out (right).

So should I adjust float at a slight downward angle, or is there something else to look at/ for? I think all the gaskets in the carb are in the right place, and as stated before it has a new needle, seat, and float that came in the carb kit.

Yes, I set mine at a slight downward angle. After putting the carb together, turn it upside down and try to blow through the fuel input. With the carb upside down, the float should seal off the fuel intake.

Also, is this a cork float we're dealing with here?

 

[Justin-KS]

Re: Johnson 3hp starts and dies after a couple of seconds

I did the blow test and it was sealing off, it will have to wait until tomorrow before I can set the float it at a downward angle.

I will give an update once I get the float changed.

It is a plastic float that came with the new carb kit, it's not a cork float.

 

[Justin-KS]

Re: Johnson 3hp starts and dies after a couple of seconds

Well I was able to get it to stay running after adjusting the float, but had to keep the rpms up to keep it running.

While it was running and i was messing with the low and high speed I checked the head and she was getting hot. I was still getting a good strong mist/flow.

So I shut her off, let her cool, and pulled the head gasket. The gasket was completely shot, and some of the holes in the gasket were plugged. Also there were a few drops of water on one of the pistons. The cylinders looked good though, no scratches, but a light tint of rust was present on one cylinder.

So I got a head gasket on the way, and I cleaned a bunch of gunk out of the water jacket. The gunk looked like thick grey oil; I?m guessing it was slipping past the head gasket out of the cylinder? I also removed the lower end and blew air and water up the water tube. I?m going to resurface the head using the glass and wet/dry sand paper trick.

Would you guys recommend doing/checking anything else while I?m doing this?

Thanks
Justin