First break down on the water - 70hp Johnson

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z33tec

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First motor issue since owning the boat for a couple months now.

Took the boat out with the family tonight. Ran around the lake a bit for maybe 15 mins. Stopped at one spot for a few mins. Motor fired back up no issue. Ran over to another spot and fished for an hour or so. Went to fire the motor back up to leave and wouldn't start. Sounded like it came close a couple times but just wouldn't fire up. Thank God I'm a fisherman and wasn't far from the dock, so the trolling motor was able to limp us back. If it died at the first spot we were at we would've been in trouble as it was quite a ways out.

Plan on troubleshooting it tomorrow in the driveway with muffs.

Only thing I changed since my last outting was the wide open throttle screw. It was in quite a ways and wasn't allowing me to reach max RPM per my service manual and adjusted it accordingly. Shouldn't have any bearing on starting though.

I am running 87 octane in this tank as my service manual said that was recommended. I ran 89 before and it did seem to run a bit better at low RPM but could just be in my head.

I did recently replace the spark plugs. They were the recommended ones from service manual but did notice the part number was different than the ones that were in there before. They were one letter off and I think they're the ones listed as "alternative" in the service manual.

Any ideas where to start with the troubleshooting?

Is it possible I flooded it? Since I havent owned the boat that long I wouldn't consider myself an expert when it comes to starting a 2 stroke, but I've become fairly confident.

Usually after running, it will fire right back up on first crank without any choke or throttle. Sometimes, if we stop to fish a while, I'll have to fuss with the choke and throttle a bit, but it's never been an issue.

Any thoughts are welcome.

Sent from my SM-G975U using Tapatalk

 
2 things I've found to check when a motor has trouble starting after it's been warmed up...

Plug gap... make sure the plug gap is correct. Too big a gap can do it..

Gas tank has been out in the sun and high pressure has made the fuel pump or hose malfunction. Did you squeeze the bulb when trying to start and it felt squishy or wouldn't get "firm" ? I'm not really sure exactly how this happens... but it does...
 
Shaugh said:
2 things I've found to check when a motor has trouble starting after it's been warmed up...

Plug gap... make sure the plug gap is correct. Too big a gap can do it..

Gas tank has been out in the sun and high pressure has made the fuel pump or hose malfunction. Did you squeeze the bulb when trying to start and it felt squishy or wouldn't get "firm" ? I'm not really sure exactly how this happens... but it does...
I will check the gap on the new plugs. I'll be honest, I've always just installed new plugs and always ignored the gap measurements. Maybe this time it finally caused an issue.

Did check the bulb and it felt firm. It was late and I have built in tank, so sun not issue.

Thanks!

Sent from my SM-G975U using Tapatalk

 
If the spark checks out, I'd be looking at fuel. Especially if you recently filled before your problems.

Sent from my CLT-L04 using Tapatalk

 
PLUGS - The 1st thing I always check for hard starting is a proper plug gap. Use only Champion plugs in that motor and gap at 0.030” regardless of what another gap spec (typically 0.028”) you might see, as OMC made the change years later.

FLOODED - The recipe for flooded OBs is to close the choke & start at highest RPMS in neutral, just be ready to immediately back off the throttle once she clears and fires.

OTHER - Some motors are like women ... YOU need to find out what SHE wants to start up & turn on. Maybe that OB needs a little more throttle in neutral to start up after being off for a while?

You say you have the OEM manual, do a sync & lync and check for where the roller cam is.
 
Guys...as far as the spark plug gap goes. As long as it is close it should fire. .002 will not make a difference. That ignition system has enough energy to fire a quarter inch gap unloaded with ease. Now, using the correct plug can make a difference.
It was mentioned that the plug may not be correct. If the alternate plug is a surface gap those can be difficult to get an engine going if it is flooded.
Let's see if he has spark to begin with and go from there. Remember.....start with the basics before making suggestions.
 
Update from today. First things first, I checked the plugs. The gaps were a little under recommendation so I adjusted them back open to .030 per service manual (and Dale.) Checked the fuel hoses for any kinks. The line that's under the cowl does have a bend that it needs to make, but it didn't seem too bad. I tried to ease it up a bit but it's probably no worse than it always was before this. One other thing I did do, but didn't "seem" to be an issue, is unclip and re-clip the kill switch. Not sure if I mentioned before, but I had a 3 and 7 year old aboard at the time. They pretty much never sit still and could get into anything. God only knows what they bumped/touched while I wasn't looking, so I did that for good measure.

So after running through those checks, put the engine on muffs in the driveway and she fired right up. One thing to note, since I wasn't in the boat and started it just reaching over the gunnel, is that I never pumped the bulb. Maybe I don't need really need to be doing this unless it sits for a long while?

So... where do we stand... I'm thinking the most likely thing that happened is that I may have flooded it. Cranking it while using the push-in-key choke and fast-throttle to no avail probably made matters worse. I'm guessing if I backed off and gave it 10 mins it might have started.

Or..... it was one of the other things I checked lol... #-o #-o #-o

EDIT: Also to note, I am using the recommended plug from service manual since someone mentioned it. The ones listed as "alternate" were in there previously and I replaced them.
 
You shouldn't have to pump the bulb after it is warmed up that being said even if it had been pumped again it really shouldn't make any difference. Now that kill switch could be a whole 'nuther issue, BUT it shouldn't cause a no start issue unless it was detached.
 

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