70HP Johnson Power Loss (HELP)problem solved

[Bass Runner]

Well just fixed one problem now i have another, it is a 1974 70hp Johnson model no.70ESL74M, i had a idle problem which i fixed by changing carbs, now it will idle and when you gas on it it will take off like a rocket but about 3/4 throttle i will die back to about 1/3 throttle and will go no faster, it acts like it is loosing one or maybe two cyl. I checked the plugs and they were all three clean but wet with fuel, tried firing it back up and it started up right away tried to take off and it did the same thing every time, checked the fuel bulb it was hard, and tryed choke and all it did was die down so i don't think it is fuel related, i have done link and synch the coils all look good , the fuel filter is clean, anyone have a idea where to start looking?

 

[rickdb1boat]

Re: 70HP Johnson Power Loss (HELP)problem solved

Bass Runner <br /><br />Can't remember all the other postings, but have you checked the fuel tank vent and replaced the primer bulb and fuel fittings? Could be a bad bulb or air leak at the fittings..

 

[Bass Runner]

Re: 70HP Johnson Power Loss (HELP)problem solved

Yes this is a project boat and the vent on the 18 gal tank is new and no kinks in the hose, the fuel line and primer bulb is new. All the fittings are tight, like i said i think it is a ignition problem but where to start, it keeps running but when you gas on it zoom it takes off but then just dies down to about 1/3 throttle and will run no faster, acts like it is loosing a cyl. or two.

 

[Bass Runner]

Re: 70HP Johnson Power Loss (HELP)problem solved

By the way can anyone tell me how to set the link and sink on this motor i may have it set wrong, i know the butterflys are wide open but not sure about the advance.

 

[Bass Runner]

Re: 70HP Johnson Power Loss (HELP)problem solved

Checked the timing today and it is set right, hot blue fire to all three plugs, what could cause this thing to loose it and bog down like it is?

 

[Bass Runner]

Re: 70HP Johnson Power Loss (HELP)problem solved

Well checked the carbs and advance seems to be alright as far as linkage, checked the jets in the carbs, they are clean, and the floats are set right, changed the fuel pump, what could cause this thing to run like a rocket up to about 40mph then drop back to about 20 or25 and not run any faster, have checked the vent on the tank and the primer bulb stays hard, and when it does it choking it just kills it, any ideas?

 

[OBJ]

Re: 70HP Johnson Power Loss (HELP)problem solved

Runner, tell us about the carb change. Why you did it and where did you get the carb(s)?<br /><br />EDIT: Just thinking.....sounds like the fuel flow to the carbs can't keep up with the high rpms. Still would like to know about the carb change.

 

[Bass Runner]

Re: 70HP Johnson Power Loss (HELP)problem solved

Ok the original problem was that it wouldn't idle in gear, the tech i got the carbs. from checked them after i changed to the carbs he gave me and said there is a little plastic seat that goes under the low speed jets that was bad he called it a bearing and it is about the size of a bb, it is a seat for the jet, it idles fine now and accellerates like a rocket up to about 40mph then just bogs back to about 20 or 25, sounds like it's loosing a cyl, all plugs are wet with fuel but it never dies and still idles smooth, changed plugs and took it back out same thing, if i ever get this thing running right it will be a bomb.

 

[ferrans]

Re: 70HP Johnson Power Loss (HELP)problem solved

problem sounds similar to the one I just posted. watch for my replies to. duckslayer

 

[Bass Runner]

Re: 70HP Johnson Power Loss (HELP)problem solved

Originally posted by duckslayer:<br /> problem sounds similar to the one I just posted. watch for my replies to. duckslayer

I checked your post and gave you a check to do, don't know if it will help you solve your problem but can't hurt to try it.

 

[Bass Runner]

Re: 70HP Johnson Power Loss (HELP)problem solved

Problem solved, the bottom carb needle and seat was leaking fuel at high rpm, never seen this before, at idle it did fine but let the rpm get up and it would leak and flood the bottom cyl. now its overreving got to increase the pitch on the prop to bring it down about 600rpm

 

[nofishjoe]

Re: 70HP Johnson Power Loss (HELP)problem solved

Hey I am having the same problem with my 60 horse and have tried everything.... Did you rebuild your carb or were you able to fix that needle a different way. Help would be appreciated.....Thanx

 

[Bass Runner]

Re: 70HP Johnson Power Loss (HELP)problem solved

yes i rebuilt the carbs but i got a bad needle and seat in one kit, wouldnt hold under pressure, you might try taking the drain plugs out and fulsh the carbs if that dosn't help then go get the kits they are about $10 per kit so about $30 for all the carbs on your motor. hope this helps do you have one carb leaking fuel when not running and you pump the primer bulb? you will have to take the silencer off to see because if one is leaking it will run out the drain on the silencer and you won't see it.

 

[nofishjoe]

Re: 70HP Johnson Power Loss (HELP)problem solved

have the silencer off already and no leaks that I saw.....Replaced all the plugs and it sounds ok but not able to tell till tomorrow when I get it on the water. Unless it is under load the boat is fine.

 

[Bass Runner]

Re: 70HP Johnson Power Loss (HELP)problem solved

Originally posted by nofishjoe:<br /> have the silencer off already and no leaks that I saw.....Replaced all the plugs and it sounds ok but not able to tell till tomorrow when I get it on the water. Unless it is under load the boat is fine.

does your primer bulb stay hard when you are out running, did you check the filter? check your fuel lines going to the motor for cracks. does it sound like its missing when you loose power or does it just sound like its slowing down smoothly? if it isnt missing (motor shaking and all that junk) it is probaly flooding (was the plugs wet when you pulled them) if its obviously missing then it may be in the electrics (coil-powerpack-or plugs) hope this helps.

 

[nofishjoe]

Re: 70HP Johnson Power Loss (HELP)problem solved

plugs are wet and it slows down in a hurry.......

 

[Bass Runner]

Re: 70HP Johnson Power Loss (HELP)problem solved

sounds like its flooding instead of loosing fire check the float levels you sure the carbs arnt leaking fuel in the throat of the carbs? are you running L77JC4 plugs? and is the advance going to the stop when you advance the throttle?

 

[nofishjoe]

Re: 70HP Johnson Power Loss (HELP)problem solved

YEah I thought I was flooding out too but not real sure....Primer bulb does not get hard at all. I can pump the thing all day and it still not going any faster....Just replaced all the lines and bulb last year too.. This all started last year but went away for a bit

 

[pjb]

Re: 70HP Johnson Power Loss (HELP)problem solved

What fuel bulb are you using, if its a tempo replace it with any OEM bulb, your problerm could be many things but a bad bulb is an easy one to rule out

 

[Bass Runner]

Re: 70HP Johnson Power Loss (HELP)problem solved

Have you checked the fuel filter and changed the fuel pump could be the pump is working just good enough to start and run but at wot it cant keep up, be careful if it's the pump and its running lean at wot you will blow it up.