Seventy Johnson Boggs on Acceleration

[loujoe]

Help Guys
I have a 70 hp johnson sat up two years, I have replaced power pack because It was only firing on 2 cyl's. Fixed that took it for a spin idled rough and no acceleration. I had to play with the choke to get to wot. I figured carbs, so I rebuilt them jets and bowls very clean soaked them anyhow. Floats out of adjustment, installed kits. Performed link and sync. Timing off just a little took it to the lake ran beatifully except for acceleration, still bogging but not nearly as bad just had to push choke once. So I repleced fuel tank, all fuel lines form tank to carbs. installed fuel filter & set of coils. Can anyone help me I am scratching my head. Yes the bulb stays hard during acceleration the compression 155 to 118 lbs. Thanks Tim

 

[kenmyfam]

Re: Seventy Johnson Boggs on Acceleration

Help Guys
I have a 70 hp johnson sat up two years, I have replaced power pack because It was only firing on 2 cyl's. Fixed that took it for a spin idled rough and no acceleration. I had to play with the choke to get to wot. I figured carbs, so I rebuilt them jets and bowls very clean soaked them anyhow. Floats out of adjustment, installed kits. Performed link and sync. Timing off just a little took it to the lake ran beatifully except for acceleration, still bogging but not nearly as bad just had to push choke once. So I repleced fuel tank, all fuel lines form tank to carbs. installed fuel filter & set of coils. Can anyone help me I am scratching my head. Yes the bulb stays hard during acceleration the compression 155 to 118 lbs. Thanks Tim

155 to 118 ??? Thats quite a wide span. Is this correct or is it a typo ????
What are the readings on each individual cylinder ???

 

[loujoe]

Re: Seventy Johnson Boggs on Acceleration

I am sorry it was a typo it should say 115 to 118.

 

[kenmyfam]

Re: Seventy Johnson Boggs on Acceleration

Is your fuel tank vented correctly ????

 

[wavrider]

Re: Seventy Johnson Boggs on Acceleration

Sounds lke it could be a weak fuel pump.

 

[loujoe]

Re: Seventy Johnson Boggs on Acceleration

Yes it is vented correctly. Fuel pump I have removed the line going to the carbs spun the motor and fuel spurted out quite well. Should I go ahead and put a kit in this pump.

 

[tashasdaddy]

Re: Seventy Johnson Boggs on Acceleration

model # of the motor, sounds like a fuel prob, common the jets are clean, when they are not. did you remove them and clean, or just blow thru them???

 

[loujoe]

Re: Seventy Johnson Boggs on Acceleration

I removed the jets and the were very clean.

 

[tashasdaddy]

Re: Seventy Johnson Boggs on Acceleration

Model #???

 

[kynolan2183]

Re: Seventy Johnson Boggs on Acceleration

I have had the same problem with my 70 hp.
You can look at this post
http://forums.iboats.com/showthread.php?t=187924

I have also found that when I set the link and sync for my motor that i set the trottle pickup timing on muffs at 6 degrees ATDC. Then when in the water I fine tune the idle. The idle will seem high in the drive way. In the water the link is correct at 2 degrees BTDC.

Also I set my throttle to over open the butterflies a little when I drop the hammer. The reason for this is that these motors have no accelerator pumps and when I give it full throttle I am allowing the carbs to open all the way for a brief second then back off a little. This gives the motor a squirt of gas, kind of like an accelerator pump. Once on plain I ease off the throttle to Wide open on the butterflies. Engine RPM and feel is a dead give away to wide open on the butterflies.

These motors are tricky to get correct.
Go online and pull picks of you motor with the top off looking toward the linkage and you can get an idea of where your idle screw should be.
It was a big help to me to start in an area that was close.
Kyle

 

[loujoe]

Re: Seventy Johnson Boggs on Acceleration

Your wright I did not try to set timing in drivway I took to a nearby ramp. It is about two degrees at idle. I also repulled the carbs rechecked needle and seat opperation and float level everything was all right. As far as the jets they were clean and I soaked them and blew them out on the initial rebuild nothing in the bowls very clean fuel looks great. Thanks for the web link I will check it out. I am really thankful for all the posts.

 

[kynolan2183]

Re: Seventy Johnson Boggs on Acceleration

two degrees at the ramp is good. but don't be afraid to exceed that. remember that the book is written for a new motor is great condition with no wear.

Mine runs at 1 to 2 degrees ATDC in the water when it should be at 2 BTDC.

kyle

 

[loujoe]

Re: Seventy Johnson Boggs on Acceleration

My model # is J70ELCNB 1982 70HP JOHNSON electric start and power trim

 

[tashasdaddy]

Re: Seventy Johnson Boggs on Acceleration

get your timing right and recheck your link n sinc.

 

[loujoe]

Re: Seventy Johnson Boggs on Acceleration

Petty Officer 3rd class

Well my ball sockets came in and I installed them Whow!!!! No more slop. At wot my throttle plates needed some adustment, not all the way open. Adjusted them, I order to get them to open all the way I had to back off on the throttle cam yoke retarding the base timing. So that caused me to adjust the idle screw like your picture suggested. One more question on my timing pointer postition. I followed the instructions in the manual, piston stop tool roll motor over clockwise until tdc mark cast in flywheel is aprox. 1.5 inches beyound pointer. Mark stop tool and flywheel . Roll motor over again my second mark is 4.25 inches from my 1st mark. 1/2 way bettween the two marks is 12 degree mark on the flywheel. Is my flywheel installed wrong. I thought it could only go one way. thanks for the help. There is hardly any adjustment on my timing pointer .

 

[kynolan2183]

Re: Seventy Johnson Boggs on Acceleration

I don't think the fly wheel could be installed wrong but the key could have sheard and formed a wedge of metal which could still hold it in place. That is very unlikely though. If the fly wheel was loose I would think that you could feel it by moving the fly wheel with your hands for play.

I would set the idle at about 1050 RPM on Muffs by only using the Idle advance do not let the Carbs be involved in the adjustment at all. (loosen the roller from the cam) ( by the way your motor will sound horrible, loping and shaking on the muffs)


Once you have the Idle set make sure the carbs are snapped closed and set the roller to line up on the cam at the first mark on the cam. Adjust the cam as needed to match the roller. It is a give and take thing. Use the photos to give you an idea. The link and sync instructions are good but I have found that these motors need a little shadetree work on them to run just right.

This will get you really close, next is the boat ramp.

Let me know if you still need help.

Kyle