1997 Johnson 40 no spark

[waterinthefuel]

This one has me stumped.

I just installed the used outboard I bought off of Ebay. We decided to use 50:1 gas oil even though it has VRO just to make sure the VRO is working before we go to straight gas. Well the engine missed and ran terrible and had so much oil it was unbelievable. But slowly it ran worse and worse until it finally stopped.

So we were diagnosing it as having no spark then I asked my dad where the lanyard was. He said its still in the garage. Whoa, the engine was running without the kill switch. Now we have no spark even WITH the kill switch. Doesn't this sound like a bad ignition switch? I'm sure the original is still in the box and it's almost 30 years old now. The tach was working perfect while the engine was running, but there is no spark anymore.

Would you say ignition switch related? That's what we are thinking. The engine ran worse and worse and then died. But we were running it with way too much oil, but oil doesn't kill a coil. Both cylinders are dead, no spark on either.

 

[waterinthefuel]

I disconnected the black and yellow striped wire (the kill switch circuit) and the engine started. But then it was able to be manually stopped with the switch. (shouldn't be able to with the kill switch circuit disconnected.) Then it was almost impossible to get started again, and with an inline spark checker, we can see it's got intermittent spark while running and while cranking over most of the time has no spark at all. Does this engine know about cutting a cylinder at slow no-load idle? It's a 1997 model. We eventually had a fuel hose leak so bad we think it just ran out of gas so we shut the whole thing down for now. We are getting too frustrated.

 

[racerone]

When flywheel is turning fast there should be spark on both cylinders.-----No such thing as a motor like that running on 1 cylinder at idle.

 

[waterinthefuel]

When flywheel is turning fast there should be spark on both cylinders.-----No such thing as a motor like that running on 1 cylinder at idle.

I didn't think so. But I know my dads Mariner 125 that's a 95 model has cylinder deactivation at idle to save fuel. I wasn't sure if this thing could as well.

 

[racerone]

Those 4 cylinder motors had spark on all 4 cylinders all the time

 

[waterinthefuel]

Those 4 cylinder motors had spark on all 4 cylinders all the time

No they don't.

https://www.thehulltruth.com/boating-forum/831789-can-you-remove-2-2-cylinder-cutout-off-125-mercury-outboard.html

 

[racerone]

Sorry mate.----There is spark on all 4 cylinders all the time.----The bottom 2 carburetors only supply a wee bit of fuel at below 1800 RPM.----But please explain to me how you can save fuel by stopping spark to 2 cylinders , on a 2 stroke like those 4 cylinder Mercury motors !!

 

[waterinthefuel]

Well if you cut the spark you don't burn the gas. It's not rocket science.

 

[racerone]

???----On a 2 stroke the gas would still go out the exhaust to be wasted as well.----Not rocket science.----P;ease review your understanding of how a carbureted 2 stroke works !

 

[Faztbullet]

The kill tether that attaches to the switch, is a mechanical kill. When installed and engine running, if pulled it turns key to off. Engine will start and run and kill if not installed. Sounds like switch is working as designed.

 

[saltchuckmatt]

I had that Merc.....it's called a 2 plus 4. It kills fuel to two cylinders. Pouring fuel to two cylinders with no spark makes absolutely no sense.

 

[Crosbyman]

sparks or no sparks fuel gets sucked in... then compressed (burnt or not) then pushed out the exhaust ..cutting sparks has no effect on fuel consumption

Google Search

 

[racerone]

The 2 stroke engine is a wonderful machine.----But many folks (newbies ) have a poor understanding of how they work !

 

[airshot]

I had that Merc.....it's called a 2 plus 4. It kills fuel to two cylinders. Pouring fuel to two cylinders with no spark makes absolutely no sense.

Sounds like a bad design...being a two stroke, that fuel is how they get lubrication....no lube and those cylinders would't last very long........I have a 4 cylinder Classic 40 Merc. Excellent running engine, idles very slow !! I have also owned a twin cylinder 40 hp Merc and a twin cylinder 40 hp Johnson, both used far more fuel then my 4 cylinder and had a much rougher idle. The 4 cylinder also runs circles speed wise around either of the twin cylinder engines. Not sure why engineers ever thought shutting down 2 cylinders would be a good idea ??

 

[Crosbyman]

Not sure why engineers ever thought shutting down 2 cylinders would be a good idea ??

again being 2 stroke how would they have kept up oiling the innards
if they had been able to stop the inflow of the fuel oil mix to the 2 dead cyl. .
easy to do today on ETECs and modern EFI engines with oil ONLY circulated inside the crankcase and fuel only under direct injector control and easy to shut off by computer control. .

My ETEC 75h consumes half my Merc Classic 50 did and burns only .6 L/h trolling !!

 

[racerone]

Correct , the E-tec behaves like a 4 stroke for part of the revolution of the crankshaft.---Therefor saves a lot of fuel.

 

[saltchuckmatt]

I had purchased my boat with that 2 plus 4 knowing I was going to replace it.....I sold it as a bad engine not knowing that was how it operated. A marine mechanic purchased it from me and explained how it worked....it was then that I purchased my first e-tec

That 2 plus 4 was weird, after you started to throttle it up it would start to move and then jump out of the hole. Seemed like it had issues!