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Old 01-17-2021, 02:00 PM   #1
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Why wont my Mariner 8 start?

I was doing odd jobs in my old, US built, 2 stroke, Mariner 8 powered tender, left it idling for a few minutes and it stalled. No amount of pulling would restart it. So far:
Cleaned carb
2 carb kits
2 sets of plugs
New cdi

Kill switch works properly
Good compression
Good spark
Fuel seen on plugs while attempting to pull start

It's hard to imagine a simpler engine so with fuel and spark it should start but I've got nothing close. Not even with a shot of starter fluid.

A OB mechanic I trust spent several hours on this thing still with no joy

Have I missed something?

Thanks
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Old 01-17-2021, 03:00 PM   #2
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I have a Merc that's wall art. Same issues. The trick was to take it to an outboard shop, pay about $300 and run it for a year or two and then repeat.
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Old 01-17-2021, 04:31 PM   #3
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Originally Posted by GoneDiving View Post
I was doing odd jobs in my old, US built, 2 stroke, Mariner 8 powered tender, left it idling for a few minutes and it stalled. No amount of pulling would restart it. So far:
Cleaned carb
2 carb kits
2 sets of plugs
New cdi

Kill switch works properly
Good compression
Good spark
Fuel seen on plugs while attempting to pull start

It's hard to imagine a simpler engine so with fuel and spark it should start but I've got nothing close. Not even with a shot of starter fluid.

A OB mechanic I trust spent several hours on this thing still with no joy

Have I missed something?

Thanks
Test to see if there's actually any spark.

edit, never mind
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Old 01-17-2021, 05:04 PM   #4
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Good spark on both cylinders? Maybe the switch box failed?
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Old 01-17-2021, 05:19 PM   #5
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Good spark on both cylinders? Maybe the switch box failed?
Clearly visible spark on both plugs.

Kill switch allows and kills spark as intended

Thanks
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Old 01-17-2021, 05:22 PM   #6
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I have a Merc that's wall art. Same issues.
Tried that. Just leaks oil on the carpet and is so ugly that my wife complains.

Thanks
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Old 01-17-2021, 07:28 PM   #7
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2 cycles use one or two flapper valves as a fuel pump somewhere on the side of the crankcase. I cannot for the life of me remember the specific name.

If they or the seals they operate against fail then the engine won't get fuel. They will show on a parts dwg.

I'm going to ask "Are you sure that dirt did not get into the bowl and plug a jet". Is there a tiny filter between the tank and the carb? If not then dirt could have entered. I do see you cleaned the carb but dirt, if not filtered, could have entered from the tank again.

One thing I got caught on a couple years ago was the crankcase split line can lose its seal allowing air to enter. MAYBE this is your case but nonetheless consider it as a last resort. My engine would run untill it warmed getting me two miles away and then when I went to idle it quit. Cranking was usually fruitless. One thing though was if I could get it to sputter, I suspect my fiddling allowed it to cool a bit so sealed the leak, and sputter long and well enough to get it to rev up to normal running speed it would continue. I think that even though some small amount of air would leak in it was not enough to stall the engine IF I COULD GET IT UP TO SPEED. But the next time I went back to idle it repeated the [process.

Normally I had to row back.

I finally gave up and took it to our local O/B expert. He has had to reseal the crankcase split on several engines. As they age the seal gives way.
My engine is an 8HP Yamaha about 25 yrs old. I wonder if your Mariner has done this also.
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Old 01-17-2021, 08:37 PM   #8
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This is why I'll have an electric outboard when this dinghy motor dies.

The gas is FRESH? The plugs are gapped to spec? There's not a mud dauber nest in the intake? It's not being flooded with too much gas (you didn't put the needle or the float in upside down when you rebuilt the carb? I've done both)?

Good luck
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Old 01-17-2021, 08:47 PM   #9
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Does it have a kill switch that takes a plastic key? Mine was loose this summer. Only desperation made me remove and replace it. Started right up. Same thing happened to a friend.

Rob
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Old 01-17-2021, 09:57 PM   #10
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Thanks guys.

Yes the fuel was old and dirty but all filters, including the small one immediately before the carb have been changed or cleaned. Fuel was replaced and the mechanic also ran it from his own totally separate workshop tank. The fuel pump gaskets and diaphragm were changed with the carb kits. Note that the engine wont fire even on artificially added starter fluid.

The OB has no intake. The carb sucks directly from under the cowling

The start/stop switch allows/isolates spark as intended. A solid spark is present.

Wierd that there is good fuel and spark but no starting or even spluttering. ��

Cheers
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Old 01-17-2021, 10:42 PM   #11
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I'm not sure you understood what I was getting at about the crankcase split line. If that is not sealed, ie; lost the seal, then air can enter the crankcase instead of pulling air through the carburettor resulting in no fuel.

I will admit that it should at least spit back with starter spray but try
talking to your mechanic.

It was mine that knew it was a possibility. Once that was taken care of it ran.


Have you tried to simply bypass the E kill switch?


REED valves are what I was trying to remember.
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Old 01-17-2021, 10:47 PM   #12
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Perhaps a compression check? Two cylinder engine could be a blown head gasket. That would keep it from starting.

James
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Old 01-17-2021, 11:08 PM   #13
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Originally Posted by C lectric View Post
I'm not sure you understood what I was getting at about the crankcase split line. If that is not sealed, ie; lost the seal, then air can enter the crankcase instead of pulling air through the carburettor resulting in no fuel.

I will admit that it should at least spit back with starter spray but try
talking to your mechanic.

It was mine that knew it was a possibility. Once that was taken care of it ran.


Have you tried to simply bypass the E kill switch?


REED valves are what I was trying to remember.
Thanks. You were right: I've never heard of it. I'll follow up.

The kill switch bypass didn't improve starting and seemed to function in both on and off when we tested spark
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Old 01-17-2021, 11:11 PM   #14
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Perhaps a compression check? Two cylinder engine could be a blown head gasket. That would keep it from starting.

James
Thanks. Compression indicated at ~95psi.
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Old 01-18-2021, 06:21 AM   #15
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Those earlier Mariner 8s had issues with flooding. I think it was something about the reed valves, but also the carby float valve. I think there was a modification that needed to be done, but it was not as a result of a general recall, so yours might have been missed. I know after I had mine fixed it started first pull virtually every time. Before the fix it was an absolute pain, right from new. That was about 1984 though.
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Old 01-18-2021, 07:56 AM   #16
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I am a primitive ,a shot of ether will tell if its an electric or a fuel problem.
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Old 01-18-2021, 08:36 AM   #17
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Pull plugs give each cyl a shot of WD40 put plugs back and it should run a second or 2. Might be enough to start fuel pulling thru
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Old 01-18-2021, 09:54 AM   #18
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I am a primitive ,a shot of ether will tell if its an electric or a fuel problem.
That's true in almost every practical case.

Your thought though jogged a another thought. Maybe there's something a bit more serious going on.

Is the timing off? That could at least theoretically be the problem.

I have no idea how timing is adjusted on these relatively modern small engines. (It's a skill that will be getting updated this year.)
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Old 01-18-2021, 06:10 PM   #19
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Thanks for all the suggestions guys. Unfortunately, none got to the root cause but a luckily a paint job and decal kit now has it starting first pull every time and making stacks more power:
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Old 01-18-2021, 09:21 PM   #20
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If it won't fire on either it's got weak spark
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