1990 Johnson 70 Cutting Out

[ChaseK3]

Okay guys, this post may get a little long, but I would appreciate any help I can get if you'll take the time to read through it. I bought a 1991 Stratos w/a 70hp Johnson on it. The motor was rebuilt, but hasn't been used in around 4 yrs. On advice I recieved here, which I'm thankful for, I took it to a mechanic (I didn't even start it until I had it checked out). The mechanic replaced the choke and did a couple of other things, but said that everything checked out. The first time I took it out it jumped up and ran like a scaled dog. I shut it down to fish. When I restarted it idled and ran up to about 3000rpm, but kept cutting out and wouldn't get on plane. I chalked it up to some bad gas. The next time I took it out it did the same thing. I called the mechanic and he told me to spray some cleaner through the carbs and that would fix it. I pulled and drained the gas tank (and cleaned it with berrymans, but I didn't run the berrymans through the engine), replaced the fuel filter, primer hose and bulb, put in new spark plugs, and ran the cleaner through it (I can't remember the name of the cleaner but I got it from bass pro shops). Immediately after this I ran up and down Joe Pool. I know that I started and stopped at least 15 times with no problems at all. Next time out, it started cutting out again. I ended up rebuilding the carbs and I pulled the VRO pump off and cleaned it out (I should probably mention that I had the mechanic unhook the VRO and now I am mixing the gas manually). After doing the work I took it out and it ran pretty good up to 5000rpm, but would cut out above that, later that night I was able to get all the way to WOT running 5700rpm and 40 mph. Last night I went to Eagle Mtn. I started and idled great, as I was leaving the marina I tried to open it up and it started cutting out around 2500rpm. My friend and I ended up idling around to our fishing spot. When we were done fishing I decided to try opening it up. I eased into the throttle, and it went up on plane. I could run it up to about 5000rpm, but couldn't run WOT. I don't think that it's overheating (no alarm and I've tested the horn circuit), the primer bulb is staying hard, and I've checked the spark with a spark gap tester (big blue spark of almost 1" in my drive way at idle with the earmuffs on the motor). I am really confused by this. Help please!!!!!!!!!!!!!!!!!
I also did a compression check. #1 was 110, #2 was 120, #3 was 100

 

[tashasdaddy]

Re: 1990 Johnson 70 Cutting Out

Welcome, to iboats. # 3 is low, but not terribly, as you want them within 10% of each other. try a decarb and see if it will bring #3 up. also take an induction timing light next time. connect to battery as normal, then when it starts cutting out, connect to each plug wire and watch for intermittent spark. an other thing you can do is at night, with the cover off, start engine on muffs, and watch for lightning, from the plug wires, shorting to the block. cracked wires will do this. last item i can think of is a partially clogged highspeed carb jet. good luck and let us know what you find.

 

[ChaseK3]

Re: 1990 Johnson 70 Cutting Out

Thanks, I'll do that. On another forum I've had several guys tell me to try champion spark plugs versus the Denso's that I am currently running. They said that theirs won't run on anything other than champion no matter how badly they want them to. Any other advice would be welcomed as well.

 

[tashasdaddy]

Re: 1990 Johnson 70 Cutting Out

the engines were designed to run on champion. let me know what you find.

 

[ChaseK3]

Re: 1990 Johnson 70 Cutting Out

I replaced the plugs today with the Champions that the owners manual says to use. No difference. I do have a question though. How hard is the primer bulb supposed to be after the engine is running. Everytime I had the problem today I reached back and was able to squeeze the bulb a couple of times. It definitely was not what I would call hard. Also, after I tried the squeezing method a couple of times I was able to plane out. It still ran rough, but I got up to approx. 4500 rpm. I'm beginning to think that I need to replace the VRO pump with a fuel pump. Any opinions?

 

[tashasdaddy]

Re: 1990 Johnson 70 Cutting Out

when you pump the bulb you are pumping gas thru the fuel pump into the carb, until the carb bowl is full, the needle float value closes, not allowing anymore fuel in, thus pressure builds up, making the bulb hard. when the engine starts to use fuel, the float opens, and the pressure is released, the fuel pump then sucks gas out of the tank, and pressurizes the carb. before you go spending several hundred dollars on a new pump. do the things i posted above. the don't cost anythng. post the results. let's eliminate the electrical. and don't go just throwing parts at it.

 

[ChaseK3]

Re: 1990 Johnson 70 Cutting Out

What is an induction timing light? Is it different than a regular auto timing light. I know that I need one that works for two strokes because of the difference in four strokes. Also, what are the timing marks for cylinders 2 and 3? Are they the same as #1?

 

[tashasdaddy]

Re: 1990 Johnson 70 Cutting Out

an induction light is the one the clips on to the spark plug wire, so you can change it from plug wire to plug wire with out have to remove the plug wire from the plug, and shut the engine down. i don't have manual for your engine so i can tell you the marks. the main thing we are looking for is the intermittent spark, causing the failure, so we can isolate whether it is a coil, wire or power pack.

 

[ChaseK3]

Re: 1990 Johnson 70 Cutting Out

Thanks. Do I have to do the test on the water under load or can it be done on a water hose? One of the guys I work with may have a timing light (he has everything else). I'll do some tests and let you know.

 

[mikesea]

Re: 1990 Johnson 70 Cutting Out

when you say cutting out,does that mean totally shuts off,or the engine kinda fades til stalls,if it just cuts off,I believe it could be an electrical prob,like key switch going bad,or a powerpack wire,specifically the yel black pinching and grounding,another thought,the mechanic????he told you to spray cleaner through the carb throat,is this guy a real mech.I say this only because ,and suprised no one else said it,that does nothing for a carb prob.also,he may have done little in the way of helping with thought like that.if the problem is fuel, and you seem to have helped by going through your carbs,posting increase of speed and rpm after servicing by you,I'm thinking,either the passages in 1 or more carbs still had crud that didnt come out,but the service did clear up some,or ,your fuel system,including the engine fuel lines and filter may have still had gunk and re contaminated your carb or carbs,if you dont have a water fuel seperater,type like an auto filter,get one,pull it often and drain in clear jar allowing you to see if water or crud exists in tank or lines

 

[Kevin W]

Re: 1990 Johnson 70 Cutting Out

I would agree that a water separating fuel filter is a good investment.
Last year i was having alot of water issues until i got one.
it does not take alot of water to make an engine cut out.

 

[tashasdaddy]

Re: 1990 Johnson 70 Cutting Out

in the water under load just like when it messes up.

 

[ChaseK3]

Re: 1990 Johnson 70 Cutting Out

Turns out it was the powerpack. It was fading out under load, and finally gave out altogether. I was sure that it was a fuel problem until the spark test was done under load. I hope this post can maybe help someone else out in the future. Thanks for all of the input guys. I will definitely be a regular on here.