70 hp Johnson problem

[kwbrian]

I recently purchased a very used skiff with a 70 hp Johnson attached. The bill of sale says it is a 84 johnson with a 95 powerhead. After practically rebuilding the boat itself I took it out for a test run. I warmed up the motor and idled up the channel with it running very rough. It stalled several times but I was able to restart it by pushing the choke and giving it some throttle. Sometimes full throttle. When I had some searoom I opened it up and found that it would go like the wind. Then it would loose power. I could play with the throttle and sometimes it would pick up and go again. Sometimes it would just bog down and stall out. It was often hard to restart. But not always. Several times when restarting the throttle would stick at high rpm's. Running at idle and just above was not easy. The motor would stall if any throttle way applied. I did manage to make it back to the dock and found that a plug wire had become disconnected. After reading some iboat forums I found that having a plug wire off would create one of the symptoms I was experiencing. That of having a difficult time accelerating after a low speed run. The other symptoms seemed to point to a fuel problem. Knowing that the boat had been stored for over a year and not knowing if the fuel system had been properly conditioned for storage I decided to remove and rebuild the carburetors. I did so by first taking them apart and soaking them in carb cleaner. I then rebuilt what I could using a new kit for each of them. I was not able to get the needle valves out as they were stuck and the slots were messed up from what looked like a previous attempt at removing them. I made sure I cleaned them very well before reassembling the carburetors. I should mention that I did not remove the plugs, inspect and clean those areas. Then I decided to replace the fuel tank, the fuel lines to the motor ( I did find water in the fuel line off the old tank ) and add a fuel water separator filter.
New test run. I idled down the channel very smoothly. No stalling and the motor answered to the throttle without any sign of bogging down. When I could I opened it up and was surprised at how fast she would go. I ran her at about 25-30 kts ( I estimate she will do aprox 45-50 kts )for several miles then pulled the throttle back to idle. Then it happened. When I gave it gas it stalled. Restarted ok but would bog down and stall when I gave it gas. This would happen sometime and sometime it would respond like it is supposed to. When I was going back to the dock I found that the motor did not want to run at idle speed. It would run better with just a little throttle. But rough.
That's what I think I know. Any help would be greatly appreciated. I need fresh thinking to keep me from going off in the wrong directions.
I have added a photo of the motor before I removed the Carbs.

 

[mikesea]

Re: 70 hp Johnson problem

Take a clear jar or can ,empty your water seperator,let us know if you find water,if you do ,drain the carbs by removing the brass plug on bottom and get clean gas in there immediatly,be sure you get clear gas through all lines including any other filter you may have, and run the eng,Report back

 

[kwbrian]

Re: 70 hp Johnson problem

There is no water. Not a drop.

 

[mikesea]

Re: 70 hp Johnson problem

Is your tank vent working or open?the fuel ball pointed in right direction,if your fuel hose has a snap connection is the oring inside worn,sucking air,do you have a VRO fuel pump or the older style with a round conection that has a slottedscrew ,if older,open and check the screen inside and be sure it has no crud,did you sync and link the carbs,. "Several times when restarting the throttle would stick at high rpm's." Has that happened any more.Check and be sure the timing plate under the flywheel tah throttle controls is working ok,Also the large throttle arm that gets controlled by the cable,there is an inner and outer part,often these parts get sticky ,especially the inner,that controls the timing,if it sticks your timing may me getting screwed up.There are plastic bushings inside.Make sure these parts move freely,Undo all conections without changing the settings,take the large bolt out,carefuly,there is a spring inside.You may need to clean and lite grease these control parts

 

[kwbrian]

Re: 70 hp Johnson problem

The tank vent is open and venting. The fuel ball is pointed in the right direction, but looses pressure after a few seconds. The fuel hoses and snap connections are new and there is no evidence of any leak.I do not know which fuel pump I have. I could not find a round connection with a slotted screw. I will post a photo. Maybe you can tell me from that. I did not sync and link the carbs. I have read about doing so but not how to do so.
The throttle did not stick at high rpm's again after reinstalling the carbs.
The plate under the flywheel moves when I advance the throttle. The large throttle arm appears to be working but I do not have the daylight left to disassemble it this evening. I will do that in the morning.
Thanks for the help.

 

[mikesea]

Re: 70 hp Johnson problem

Ok ,you have a VRO pump so forget about the round thing.The ball squeezes hard but becomes soft BEFORE you run.Thats not good,but after is.The carb floats should hold it firm for a good bit of time .Did you try squeezing the ball as the motor surged.If not,its a sure fire way to determine if fuel pump or a blockage of some type after the ball is there.Be sure all hosesafter ball are not kinked.Try running again squeezing ball during trouble,.Your correct with the surging leads to fuel ,what happens isUSUALLY one or more of the carbs run dry ,get a splash eng runs fast ,drinks it up and so on.So either your floats are not adjusted correctly,limiting the fuel quantity,fuel pump is going bad,dirty carbs,kinked hose assy,bad ball,or something toward tank.Now elimate all you did.You can try a new ball,but do the squeeze test. Does your eng have an inline filter up by the fuel pump,if so did you change it?You can bypass it since you have the other filter,but put it backafter test.

 

[kwbrian]

Re: 70 hp Johnson problem

I removed the large throttle arm bolt. Cleaned and lubed the internal parts. All seems to be working fine there.
I replaced the squeeze ball and the inline filter. The ball stays firmer now but did not change the way the motor runs. I tried squeezing the ball while the motor was running rough and when it was trying to quit. That did not help.
There are no kinks in the fuel lines and I found no leaks.
I have to keep a little extra throttle going while it idles. When I push the throttle all the way in the engine quits. It is also very hard to start. Should I try to link and sink? Or maybe remove the carbs and check them again?

 

[mikesea]

Re: 70 hp Johnson problem

bEFORE YOU TAKE THE CARBS OFF AGAIN,CLOSLY INSPECT ALL THE CONNECTIONS TO YOU COILS,SMALL ORANGE WIRES,GROUNDS,REMOVE THE PLUG WIRES AND MAKE SURE ALL CONNECTIONS ARE RUST AND CORROSION FREE.tHEN RUN ENG ON MUFFS,AS IT RUNS,REMOVE A PLUG WIRE ,ONE AT AT TIME,SEE IF YOU HAVE A MISFIRING CYL.i SHOULD HAVE READ YOUR POST OVER,i THOUGHT YOU WERE SOMEONE THAT TOLD ME YOU RAN A SPARK AND COMPRESSION TEST.iM WONDERING IF YOU MAY HAVE A DEAD CYLTHAT CUTS IN AND OUT,COULD BE SPARK OR GAS.wITHOUT A GOOD SPARK TESTER ITS HARD TO TELL.bUT YOU CAN RUN THE ENG IN WATER AND ONE AT A TIME SEE IF THERE IS ANY CHANGE ON PERFORMANCE.iTS THE POOR MANS TEST,TAKES A BIT OF TIME OR BORROW A TESTER.iM PUTTING MY FAITH IN YOUR CARB REBUILD,SO i TAKE IT THATS OK.dOES CHOKING WHILE PRB.SOLVE ANYTHING

 

[kwbrian]

Re: 70 hp Johnson problem

It may be spark. I found a plug wire that was not in good shape. It will have to wait until tomorrow. No one that has what I need is open this afternoon.
I did a compression test. 120, 115, 118.
All of the ground coil wires seem alright. There was some tearing in a couple cover boots. I repaired those.

 

[mikesea]

Re: 70 hp Johnson problem

i would buy a set of good wires,especially if the tears were on the plug wires,comp is great

 

[James R]

Re: 70 hp Johnson problem

Possibly something simple. Your saying that the fuel fittings are new may be the clue.
I have had numerous issues with fuel fittings not fitting correctly. They can look the same but they may not be opening or leaking air. The line fitting may not match the tank or the motor fitting may not match. If you have others to try do that first.

 

[kwbrian]

Re: 70 hp Johnson problem

I have replaced the plug wires. Cleaned and inspected all wiring. Replaced the fuel fittings again. No luck. In fact there is now a pronounced "cough" in the motor while at idle. At low idle it coughs and then stalls.

 

[noelfm58]

Re: 70 hp Johnson problem

Don't know if this will help or hinder you, but here goes. I've got a '78 100HP Johnson that might be a big brother to yer 70. Installed one of those glass in-line filters that are quite easy to replace once I notice too much gunk in the filter. Anyhow, deal is, when my ol cluncker gets to coughin, spittin'n overall acting up, a quick glance at my "see through" glass filter at least lets me know if the juice is flowing. Often times, if I don't see fuel running, I immediately know to look at fuel and cut down on my guessing. 'nother thing: sometimes the valves in those primer bulbs like to act up and refuse to deliver fuel. My solution is messy but it works: I remove the connector to the engine, and still holding it slightly against the male connector (so it depresses the spring just slightly AND with a large rag to collect the spent fuel ) I operate the primer bulb until fuel starts pumping; I reconnect the hose and see if I can squeeze the bulb at least 3 times - normally required to fill the empty bowls of the 2 carbs. This normally restores a coughing/stalling engine to normal operation.

One last if, maybe, perhaps: if my motor has been running for a long while (like the extended trolling that I like to do for stripers) I will once in a while experience "vapor lock" where the fuel in the carb bowl has evaporated and somehow jams those pesky valves in the primer bulb. I then have to resort to the operation above.

Hope this helps.