HELP!!! 75 Johnson 70hp, no power

[jts76240_2005]

I want to start off by saying great site guys.<br /><br />Well here goes I have recently aquired a 75 Johnson 70hp that doesn't run correct. On its maden voyage with me I gave it plenty of chance to warm up and took it for a fast run. I applied throtle and everything ran smooth up to about mid throttle. Then the poor thing fell on its face and wont rev any further. So I suspected a possible fuel blockage. I have no clue how long it may have set. Upon inspection the carbs look great and are very clean. It is my guess they have been rebuilt recently (someone scratched numbers in them 1,2,3 lol). Also what confused me was there is no adjustment for the mixture either it seems to be all preset by the jets. So I checked the fuel pump and it was spotless as well. Then I went back to basics and changed the plugs. To me they seemed a bit wet but I am not too knowledgable with 2strokes. I took it for a run again and same thing. Then all of a sudden it kicked in and went full throttle. Ran great for about a minute then fell again and has been the same way since. Every now and then it will bump a little and rev up but falls right back off. I read on here that if it was a fuel restiction that if you pull the choke it will try and go faster. So I tried this as well. This didn't work and it acted as though it wanted to die as soon as i pulled it. To me it also consumes an excessive amount of fuel. I did read as well that the regulator can cause the problem I am seeing but it seems to charge great too. It will run all day long like this and never miss a lick. Any suggestions on this would be so great.

 

[papasage]

Re: HELP!!! 75 Johnson 70hp, no power

try pumping the bulb . check see if all cylinders are firing . could be a bad coil . my 74 70 hp has 3 coils one for each cylinder . one would break down after a short run and after a cooldown a few minutes it would run a short diastance and slow down . it will sound good a rev good with a missing cylinder .

 

[jts76240_2005]

Re: HELP!!! 75 Johnson 70hp, no power

try pumping the bulb too, that made no difference. I am gonna pull the plugs again and see what the compression is. Also I will checking the coils too. Thanks

 

[jts76240_2005]

Re: HELP!!! 75 Johnson 70hp, no power

OK here goes, I pulled the plugs and compression is great on all three. So I checked for spark on all three, 1 and 2 have great spark but 3 is dead. So I switched 2 and 3 coils. Problem stayed the same. Is this a power pack problem? or could it be something under the flywheel?

 

[papasage]

Re: HELP!!! 75 Johnson 70hp, no power

check to see if there is power going to pack on the wire that feeds the 3re cylinder. i have some use ones . might be good

 

[jts76240_2005]

Re: HELP!!! 75 Johnson 70hp, no power

ok if i am checking this correctly? Sensor 1 2 and 3 all have power. and if i check resistance on all three orange wires on the opposite side while the motor is off all three have connection between sensor and orange accordingly and about the same resistance. if i check amps between orange and power pack, 1 and 2 are high but three is dead. I am assuming this means that 3 is gone.

 

[papasage]

Re: HELP!!! 75 Johnson 70hp, no power

all your switch does is grounds the power from the stator . like a lawn mower does .. battery is onley fot cranking

 

[jts76240_2005]

Re: HELP!!! 75 Johnson 70hp, no power

ok well i knew that so I am assuming that was ment for someone else. Anyways you said you might have some used ones. If so please feel free to send me and email and let me know what you want for them little things I would really like to get this thing going right again.

 

[papasage]

Re: HELP!!! 75 Johnson 70hp, no power

email me at papasage10@yahoo.com.i have 2 used ones that did work just slung a rod go down to dk1953 and read that post on his 70 1973 hp. they are the same . see if it is like yours. simular probablem

 

[almost retired again]

Re: HELP!!! 75 Johnson 70hp, no power

Hi Smitht;<br />It sounds like you can handle a multimeter ok so here goes a little info on your ignition. It all starts under the flywheel, and everthing that comes from there is AC. Most of the voltages that the manual calls for are in peak values, so if you have a regular voltmeter the reading that you get multiply by 1.414 to see what your peak value is. ( realy not nessary)<br />there are two wires from the charge coil , I belive they are orange and orange and brown,but it's been a long time. These wires charge the condenser in the power pack after being rectified, the voltage that you will read on these 2 wires while cranking should be around 200 volts AC. The other four wires going to the power pack are sensor wires that tell the power pack what coil to fire and when. The white wire is the common to the other three. From the white to each of the other three the reading will only make the meter needle move slightly on the lowest scale. The sensor coils only put out approx. 3 volts peak AC. That covers all of the inputs to the power pack. If they were good that means that the stator is ok. Now the output from the power pack is the wires that go to each of the coils. The reading between each of these should be approx. the same as charge coil voltages. (200 volts DC) as the engine is cranked. After this it only leaves the coils that you can check with a spark checker. If everthing else checked and there is no spark on any one coil then change that coil. Boy that was windy but I hope that it helps.

 

[jts76240_2005]

Re: HELP!!! 75 Johnson 70hp, no power

It is missing the voltage to the output of the third coil so according to what you have said the power pack seems to be the culprite. I will see what it will take to get one ordered. Thanks

 

[DKLINE1953]

Re: HELP!!! 75 Johnson 70hp, no power

jsmitht<br /> dkline1953 here.<br /> Call it karma/dejavue, but I've got the same thing going on(won't use the word identical). What got the mighty lady up and running. Power pack--- sounds like the lead horse in the race.<br /> Your opening salvo was right on the money. This is a grrrrreat site for info. <br /> Almost retired again if your reading this, thanks for the steering over to this one. I had focused on my posting replies and put the blinders on. Thanks for the electronics course on the simple system that makes boats go putt putt around the lake(which mine hasn't as of yet and the lake is next week).<br /> jsmitht did you get hooked up with a power pack from papasage10@yahoo.com.???<br /> Hope #3 fires up on you.<br /> Take Care dkline1953