1975 70 hp johnson problems

OLJOCLARK

Cadet
Joined
Apr 5, 2010
Messages
27
OLjo here again.Im having posting problems with my old computer,sorry about getting back.like I said before.my motor runs great at home on the water ears,but in the creek takes on a whole new deal!Spits and sputters,hard to crank,sometimes it'll runout sometimes not.The local mechanic replaced reeds and gaskets and got it a little better.Now it's not spitting gas back .He say's the compression is good.We've replaced needle valve"s and seats,the carbs are in good shape,very clean,from twice off the motor,they are seating good.When I'm at the creek and Idling I can see all 3carbs getting gas at about the same amount.What about spark advance?Think I ought to adjust some today when I try it? I replaced the rectifier at first because dirt dobbers helped rot the wires.As soon as I got it goin it would not cut off,so I ran my own cutoff switch according to I forget Who's instructions,which is working.Ive checked the coils with a spark tester and I'm gonna get the wife out after while and look at the plugs while it's running,,after I tape up my channellocks real good! The motor did set up for a year or so befor I bought it,which was last fall and I didnt carry it to the water,but it cranked good at that time. thanks for any help in advance.Any body got any low budget ideas I can try befor I carry this back to the man? Oljoclark
 

tashasdaddy

Honorary Moderator Emeritus
Joined
Nov 11, 2005
Messages
51,019
Re: 1975 70 hp johnson problems

very simple. on muffs you do not have any backpressure on the exhaust, so the motor starts easily, and idles low. in the water the motor has to blow water out of the exhaust housing to escape. set your idle on muffs at 1,000 rpms, then fine tune with the motor in the water and in gear.
 

OLJOCLARK

Cadet
Joined
Apr 5, 2010
Messages
27
Re: 1975 70 hp johnson problems

Thanks,,afterwhile I'm gonna carry it to the creek again. Got my tools packed.This morning I was reading about spark advance,and looked at mine and the advance was not moving with throttle movement . I have adjusted that for a start and instead of water ears I cranked in a barrel.It cranked and ran pretty good.I can tell the diffrence in the pressure,and I dont think it would have did that well before I moved the spark up,I hope!Is it possible to go passed a good position? Forward I mean.I have found out these older motors are easy to flood.I'm working on that touch now too.Another Question. Does the pressure in the fuel pump fluctuate in diffrent pressures also?Just tryin to learn more. Thanks for any info. OLJOCLARK
 

OLJOCLARK

Cadet
Joined
Apr 5, 2010
Messages
27
Re: 1975 70 hp johnson problems

For anyone Who's had this problem.....I tried the motor out today and it just barely ran,,until I found a sand bar to stop and work on it.No luck on adjusting the spark to fix my problem.I finally remembered that once I had a mercury 80 hp that would run out good for a while and then just quit,after scratchimg my head for awhile I took off all the fuel connectors and ran a straight line from the tank and it never did it again.So I took out the fuel male and female ends,,male on the motor,,female on the fuel line,,and it started running better. still hard to start and missing a little when running, but better!I still got issues but I'm getting closer.Any suggestions? The bubble maybe? I didn't think to look at the bubble while I was running. thanks,,,OLJOCLARK
 
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