1997 Johnson V4 115 Issues

[jb70508]

I have a 115 HP 1997 model Johnson motor. Quick rundown on the issues I am having:

Motor is hard to start. Once started it will not idle unless spark advance lever is almost at full advance. Will die immediatly when put in gear.

I have replaced the fuel lines, filter, fuel pump, gas tank, and rebuilt both carbs. Still having same issue. I purchased a spark tester and in my opinion the spark seemed weak to me. Frustrated and tired of dumping money into it with no results I brought it to my local mechanic. I got a call from them and was told that the compression is low in one cylinder and that is the cause of the problem. Was told they would pull the head to further investigate, but I haven't heard back from them yet. Compression readings were 120 100 100 and 90 according to them.

I had pulled compression readings myself before bringing it in and I got 120, 115, 105 and 104

So here is my question. I know that these compression readings aren't great, but is that really the cause of my problem? Why would the motor idle fine with the spark advanced and why did my spark appear weak? By weak I mean that I used my spark tester and I had to look very closely to see the little light bulb lighting up. Having never used a spark tester before I did not know if this was normal or not. After I had brought the boat to the mechanic, I started having problems with my weedeater. I used the spark plug tester on my weedeater and the light was much much brighter and very easy to see, so I am now thinking I was not getting enough spark out of the outboard.

Any thoughts??

 

[boobie]

The OMC service manuals used to say no more than 15 psi compression difference between cylinders. Yours are a little out of wack. JMO You could also try an open air gap spark tester. Available at most parts houses for around $8.00. Set it at 7/16 " open air gap.

 

[jb70508]

Thank you for your response. I understand the compression numbers are out spec. I was questioning why it runs fine with the spark advanced? Seems to me if the compression was causing it to not idle, it would not idle whether the spark is advanced or not. Seems like a timing issue to me. I was planning on getting the adjustable type spark tester and going from there. I do plan on tearing this motor down regardless and rebuilding it as, it will need a rebuild soon. Just don't want to rebuild the motor and still have the same problem. If it is a timing issue I would like to get that ironed out all at the same time.

 

[interalian]

Advancing spark is how idle is adjusted on 2 stroke motors. If you have one cylinder with much lower compression, you're losing some of the power the motor should be making. At idle, the motor is more sensitive to that loss of power, leading to the stalling when selecting gear.

 

[boobie]

Edit.......

 

[jb70508]

Got my engine all put back together last weekend. Fired it up with no problems. Ran it a good 20 mins at idle speed. I didn't have time to put it in the water to set my timing so I was going to do that today. I went to start her up and she wouldn't start. Plenty of gas as evidenced by the oil substance and smell coming out of my prop exhaust. I put the adjustable spark tester on the coil wires and set it for 7/16". No spark at all on any of the cylinders. So, I went inside to grab my service manual to start running some tests. Go back outside and just for the heck of it, try turning it over one more time while observing the spark tester. Good spark right away. So I hooked all the coils back up to the spark plugs and she fired right up. I'm thinking power pack may be working intermittently. Any sugggestions??

 

[ondarvr]

So what did you do it? "Got my engine all put back together last weekend"

Could be neutral safety switch, ignition switch, lanyard, loose connection, etc.

 

[daselbee]

Check cranking speed first. Must spin 250-300 to generate spark. In other words, check that before you shoot for a pack.

 

[jb70508]

I did a complete rebuild due to two broken rings. Bored .020 over, new pistons, rings, bearings, seals, water pump, thermostats and carb rebuild.

 

[jb70508]

Cranking speed is good and strong

 

[jb70508]

Even before the rebuild, I had intermittent problems with hard starting. I was thinking long before that I had ignition problems. Even before I rebuilt, I had tested with a spark tester (just the one with a light bulb, not an adjustable) and I found the spark to be very weak. The bulb would light up but only very dim. I tested it on my weedeater for comparison and the light was much brighter in comparison

 

[racerone]

Some will argue-----But take the starter apart for inspection and take an ohm reading from commutator to the stub shaft.----Should read infinity on a digital meter.-------Don't rush out and buy a new starter, inspect the one you have for no $$$ spent.----A new set of brushes may help too.---I get new brushes at local starter shop for $5.00 a set.---Some folks refuse to believe how cranking speed relates to poor starting.----And you are pushing the key in while cranking it over ?

 

[jb70508]

Pushing in the key only activates the fuel primer solenoid, right? Plenty of fuel coming out of the exhaust. Fuel isn't the issue.

 

[jb70508]

Starter is new, and cranking speed is good.

 

[racerone]

Try a new powerpack I guess.----That always fixes these issues.

 

[spybot]

Try disconnecting the (red ) plug from the boat to the engine then jump the starter to see if you get a spark while the boat circuit is disconnected.
I had a similar issue. I found i had a spark when i done this. i traced it back to a chaffed wire near the control box. After i had replaced power packs, timer base, coils ect. Its worth a shot. If you need to know how to jump the starter give me a PM or someone on here will help out

 

[racerone]

Spybot, ---Does a 97 model have a big red plug ??

 

[jb70508]

I don't think it has a red plug. The only red plug is a fuse holder that says "spare"

 

[jb70508]

So, I think I have found the problem. I found this page: https://www.boatpartstore.com/page33.asp, which lists some troubleshooting steps. After going through them, I found that step 2 indicated my problem. Bad rectifier. Ordered a new one which should be here Wednesday so fingers crossed, hopefully that will take care of my problem.

 

[jb70508]

Rectifier was the problem. Changed it out today and she runs like a champ now.