Johnson 50 HP SPL 1997 - Weak Spark / No Spark

[Loozerdk]

Hi everyone, i got the task of trying to diagnose an non starting Johnson 50 SPL for a friend.

First a bit of a story on the engine.

He just had it reparied at a local marine shop, they changed the powerpack, and did a few other things to the boat, he took the boat out, it sailed perfectly, went to pickup a friend, and the engine refused to start.

Pulled the boat out of the water, and now its standing in my driveway, but the ignition system is a little bit more advanced than i am used to, so could use a pointer.

I did print a some pages from cdi electronics, and tested a few voltages and ohm readings, but i am not sure how valid they are without a dva (Parts on the way to build one).

I had the engine disconnected from the boat wiring with no change, also had the two yellow wires to the regulator disconnected, however sometimes when letting go of the key it seems to fire for just a second, and then die again.

When using a incandescent spark tester there is a very weak flash on both sparkplugs, any tips on what to look for ?

He refuses to use the marine dealer again, so thats not an option.

Kind regards
Ronni

 

[Little Richard]

I'd start by pulling plugs see if they are fouled and make sure they are getting wet with fuel. If all checks good get a adjustable gap spark plug tester and se if spark is able to jump at least 7/16 gap consistently. Real cheap. If it fails then proceed with your test suggested by cdi. Your fuel isn't old is it?

 

[Little Richard]

If your getting spark and fuel maybe a compression test would be next in line. Maybe a grounded wire on kill switch

 

[Little Richard]

Scratch the kill switch comment if your getting spark

 

[Loozerdk]

Thanks for the answers.

Fuel was old, but has been replaced and carbs cleaned, plugs are getting wet, compression is around 150 psi on both cylinders, plugs are good, not fouled.

I am not sure if it has a killswitch, but i will check when my parts for the DVA arrives.

 

[jakedaawg]

Find the 5 pin connector at the power pack. Disconnect and jump all 4 wires that are not blk/yel.

Do you have spark that jumps 7/16" now? Yes or no.

If yes test key switch/kill switch per sticky at top of page.

If no, make your peak reading voltmeter.

 

[Loozerdk]

Find the 5 pin connector at the power pack. Disconnect and jump all 4 wires that are not blk/yel.

Do you have spark that jumps 7/16" now? Yes or no.

If yes test key switch/kill switch per sticky at top of page.

If no, make your peak reading voltmeter.

Sorry not sure if fully understood, english is not my native language.

Had the wires from the boat disconnected, and just jumped the starter solenoid, no change.

 

[Little Richard]

Go to autozone or any auto parts store and buy a adjustable gap spark tester. $8.00. Set the gap to 7/16 inch. Put one end of tester into boot on spark plug wire and other end clamped to motor or ground turn over motor and see if the spark jumps that gap consistently and strong. Check each wire. If all check ok them more than likely you are ok on ignition system.

 

[Loozerdk]

Go to autozone or any auto parts store and buy a adjustable gap spark tester. $8.00. Set the gap to 7/16 inch. Put one end of tester into boot on spark plug wire and other end clamped to motor or ground turn over motor and see if the spark jumps that gap consistently and strong. Check each wire. If all check ok them more than likely you are ok on ignition system.

I would, but the adjustable ones are very hard to come by here in Denmark, we only got the type with the bulb inside, will need to order one of ebay - its going to take at least a week before it will get here.

 

[Little Richard]

It's possible to make one using a board and nails and some wire. Hammer nails through board bend them till tips are 7/16 inch apart. Use some thick copper wire. Bend it over or whatever you need to do to get it to fit tight into plug wire boot wrap it around nail. Take another piece of wire wrap it on the other nail and connect it to engine block or ground. This should work

 

[Little Richard]

Once we determine it's getting a good spark that can jump that 7/16 inch gap consistently. We can say the ignition system is working. If the spark can't pass this test. You can start testing each component of the ignition system (stator, coil packs, power pack, timer base). Of course you will need your DVA adaptor.

 

[jakedaawg]

Once we determine it's getting a good spark that can jump that 7/16 inch gap consistently. We can say the ignition system is working. If the spark can't pass this test. You can start testing each component of the ignition system (stator, coil packs, power pack, timer base). Of course you will need your DVA adaptor.

Don't forget the easiest...key switch and kill switch, which is where we heading...Remember, Blk/Yella...kill a fella! Thats what controls the spark. He said he gets momentary good spark as he turns the key off. This has a mechanical kill with horseshoe lanyard.

You take this one Rich.

 

[Little Richard]

Might want to check voltage on battery. And make sure you connections on battery are clean and tight. The motor needs to be turning at least 250 rpm for the system to work properly. Even if not a factor it's still a good idea. As for testing the kill switch. I'm use to the older type power packs with screw in terminals. Where you can just unscrew the black and yellow wire off the pack. So for your pack with the harness. Your going to have to construct some wires with connectors so you can unplug the harness coming off the power pack and connect each pin to appropriate socket in between each one. Except the one with the black and yellow wire coming off power pack. The other options would include an expensive remote starter that plugs into harness or cutting the black and yellow wire coming off power pack. I would make the jumper wires as described in the beginning. If motor happens to start you will have to choke it to kill motor or have a wire coming off black and yellow wire from power pack so you can touch it to engine block for a ground

 

[Little Richard]

If disconnecting this kill switch creates a good strong steady spark where there wasn't one before. You probably have a wire grounding out between ignition switch and motor. Or a bad switch or lanyard

 

[Little Richard]

Just saw this and thought you should be warned- If for any reason, battery voltage is applied to the black/yellow wires (kill circuit) of the powerpack.... that alone will destroy the powerpack(s)

 

[marty53]

I'm a little thrown by the fact that everyone on here seems to state in many, many posts I've read that if you have spark, fuel, and compression your motor will start. I can state without question this is not the case, as twice in the last month for separate reasons my 50hp did not start despite these three things all checking out.

The fourth thing you need is proper ignition timing and your motor will not start at all without it. Is it possible you sheared the flywheel key (did anything get hit in the water)? Other possibilities is swapped spark plug leads/coils. (these are the two things I experienced)

 

[Little Richard]

Good point. The original post said it was worked on by a mechanic. So if the flywheel had been removed and not torqued down properly could also be the reason for a sheared key on the flywheel

 

[Loozerdk]

Sorry for the delay, got the parts in the mail today for the DVA, hoping to get a chance to work on the outboard tomorrow at some point.

I will update when there is something new.

 

[Loozerdk]

Fault located.

That marine service guy is an absolute moron, nut on flywheel was loose, key sheared.

Go figure, you would think after spending 2000 USD, it would be done right.

 

[Little Richard]

Good job.