Outboard running erratically when at an angle.

[Oldone88]

I have a 1974 Johnson 50 HP esl. I purchased the boat about 2 months ago and it hadn’t been run in about 15 years. Pulled the carbs and cleaned them. Got it running initially, but then it started running rough at idle. Determined one of the cylinders wasn’t firing during idle. Ran a compression check and both cylinders were above 150. Pulled the carb from the dead cylinder and determined I hadn’t done a really good job of cleaning it.

After a solid clean and checking the float level I reinstalled it. Ran much better, I made some idle screw adjustments and called it good. Took it to the ramp to launch, and couldn’t keep it running on the trailer good enough to launch.

I decided to take it home and start troubleshooting. Put it in a barrel of water, and it ran like a champ. Started and idled great. Took it back to the launch, and had the exact same issue. The only thing that was different, was at home the boat was completely level, where at the ramp or on the water it sits bow high.
I went ahead and put it in the water even though it was running rough, and I had to keep restarting it. I don’t have a tach but couldn’t get it to rev very high at all.
Took it home and put it back in the barrel and it ran like a champ. Started great, idled great, and feels and sounds like it’s revving high in the rpm range.
I left it idling, and picked up the front of the trailer and it started spitting and sputtering. Lowered it back down, and it smoothed out.
Figured it had to be float levels, so I pulled the carbs again, and they both seemed to be perfectly level with the base of the carb. Not sure if I should adjust the float levels either up or down to compensate for this issue.
Hoping someone has some experience with this issue or some advice.

Thanks

 

[GA_Boater]

Is the gas tank built-in or portable?

 

[Oldone88]

Portable

 

[Oldone88]

Just wanted to add that it’s a “brand new” portable.

 

[oldboat1]

Need a clean tank with nothing but fresh gas and TCW-3 oil at 50:1. No additives. Best placed at the transom -- insure it's venting properly (loosen the cap if not sure).

With a new-to-you motor, check and record compression values, measure spark with an adjustable open air tester, and change out the impeller.

 

[Oldone88]

The tank is brand new. Fresh gas mixed at 50:1. No additives. It’s located in the transom. When it was running crappy at the launch we unscrewed the gas cap to relieve pressure, it didn’t seem to affect the situation. Retightened the cap and pressurized it, no change that we could tell. Haven’t checked the spark with a tester. But it gives a good spark when grounded, And the engine runs good if level. And I have changed the impeller. Probably got less than an hour on it.

 

[oldboat1]

Get an adjustable spark tester (not the inline type), and measure spark to determine ignition condition. Perhaps a fuel pump issue(?)

 

[Oldone88]

I’m curious at to what a “spark tester” would tell me? I’ve worked on motorcycles and 2 strokes my whole life and if there was a solid spark, and it ran, the ignition system was usually good.
Are there any procedures or specs to check the fuel pump?

 

[oldboat1]

Pump the hand primer when the motor is acting up. If that cures the issue, it's likely a fuel pump problem. Do what your are comfortable with for spark testing, but in order to get a uniformly solid spark at the plug (at a much smaller gap under compression), the theory is to measure at a larger open air gap to confirm ignition strength:

 

[Oldone88]

If I were to purchase the spark tester, what kind of gap am I looking for?
I believe we did squeeze the bulb when it was running bad but I will recheck.

 

[racerone]

Confusion is everywhere.-------The ignition system on your motor was designed / engineered / built to be able to provide up to 40,000 volts to fire the sparkplug.-----It does not take that much voltage to fire / bridge a 0.030" gap on a sparkplug laying on the block.----You test the full capacity of the ignition system and it parts by presenting a 7/16" gap.-----A good system with the motor spinning at around 300 RPM will jump that gap with ease !

 

[Oldone88]

Update: I appreciate all of the suggestions to try and help during the repair process.

. I probably had the carbs off about 4 times trying to figure it out. I figured out somewhere in the middle of the troubleshooting that the engine was flooding itself at mid to full throttle. Couldnt find a reason, so i decided to replace the main jets (.058) with slightly smaller jets, to cut back on fuel. But it ended up that I couldn't find any similar style jets, in a slightly smaller size.. Decided to verify the size of the installed OEM jets, and found that one was almost .080, and the other was .070. Ordered some new OEM .058 jets, and it now runs great. It never even dawned on me. that the original jets may have become enlarged..not sure if it was from wear, or someone had tampered with the size. Anyways, just thought i would share in case it helps someone else in the future.