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Starting problem, Mariner 50HP 1992 2stroke

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kiwi9

New member
I've got an intermittent starting problem on my Mariner 50HP 1992 2stroke. Often it will start fine when I launch the boat, and goes well across the lake with lots of power. But when I try to start it again after its been OFF for a while (30 mins to 1.5 hrs) it just wont start. Starter is turning the engine, battery is strong, but it wont fire. I keep trying to start it for ~30mins (until the battery drains), then have to get towed back :-(

I've checked the obvious things:
Fuel bulb squeezed, and its hard, indicating there is fuel going up to the motor from the tote tank.
New spark plugs
2stroke oil tank has lots of oil in it
Tried with choke, without choke, with idle lever up a bit, or right up, or not up at all.
Tried turning key OFF, ON, many different times.

Then when its back at home, it starts first time (with earmuffs on in the driveway). Very annoying.
Its a 3-cylinder engine, and I tested each spark plug individually (at home) by unplugging 2 plugs at a time and seeing if the engine would start. It did start, for every plug.

Its somewhat difficult to troubleshoot it when I have the family in the boat and we're out on the water.

So I'm wondering;
1) What troubleshooting steps should I follow next time it happens?
2) What are the likely parts that would fail in an engine of this age, that I could proactively replace before I take it out again?

One guy said it could be a fuel pump issue, but would that cause intermittent faults?
 
My best guess: flooding carb. Try this:


BEFORE you shut her off on the lake, pull the fuel connector and run her dry. Don't hook the gas back up and pump the bulb until you want to leave. If she fires right up, that's the problem; if not, look for ignition issues.

Jeff
 
If you have been cranking till the battery is dead it is now time to take starter apart for inspection / ohm test.
 
Jeff is thinking it's flooding out, so disconnect the fuel hose when you shut 'er down, there might be fuel from your tank getting by the fuel pump and/or carbs. You can also pull the lowest spark plug to see if it's wet when missed start occurs. Even with hot spark, a badly flooded motor will not fire. Your fuel tank may not be properly vented, causing excessive pressure when it heats up, out in the sun for instance. In other words it's allowing air into it while engine is running, but building pressure when engine is off. Racer is indicating he has concern for the starter as it's been brutalized. These starters can be fragile compared to most automotive starters. The fuel pump issue could be gasoline leaking past the diaphragm and that would be causing the flooding while it is sitting with a pressurized tank. So it is unlikely given this scenario that the fuel pump would cause the problem. I'm sure you're pumping the squeeze bulb up when you try to restart it out on the lake and that would eliminate the fuel pump if there is a bad diaphragm. If there is a hole in the vacuum diaphragm fuel would not leak into the crankcase unless there was excessive pressure coming from the tank when you are parked.
 
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Thank you all for the prompt replies. I will try these things next time I'm out.

As part of the troubleshooting, I had recently replaced the tote tank (because the old tank breather was constantly open because the rubber seal had deteriorated), and I did notice there was some pressure (tank was swelling) from the sun heat.
 
We all agree on this one. Thinking your motor is flooding and after the return home and time passes, it will restart. The fuel that passes through when motor is at rest will not have metered oil mixed with it, keep this in mind.
 
A fuel tank always needs a vent to let air in or fuel won't move out; if the tank is swelling from heat there's a vent closed. This could lead to flooding or fuel starvation when running. Try running with the cap loose enough to let air in. This could also be a trigger problem which can be tested when motor won't start by removing a plug and see if there's spark (you can also use a timing light).
 
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Okay, say for instance you keep pumping the squeeze bulb and force fuel past the pump diaphragm and into the vacuum supply port. Does that trigger or activate the oil pump to meter oil into the carb? I'm dreaming again.....it's this nasty cold, been noticing a loss of short term memory too......now wtf did I put my cell phone charger?
 
Its the stator not a fuel problem.....shuts down, stator heat soaks and no voltage at restart. Dang CDM system is voltage sensitive...
 
So...a fast DVA check (or checking for spark at each plug wire) after it screws up is the only way to spot the 'culprit'?

Jeff
 
timguy said:
Okay, say for instance you keep pumping the squeeze bulb and force fuel past the pump diaphragm and into the vacuum supply port. Does that trigger or activate the oil pump to meter oil into the carb? I'm dreaming again.....it's this nasty cold, been noticing a loss of short term memory too......now wtf did I put my cell phone charger?
Click to expand...
Because most Mercury outboards put the oil in the line ahead of the fuel pump. That means if the fuel is disconnected it will keep pumping oil into the line. So if you pull the fuel line you are just putting more oil in the line. That means when you pump the ball the next time there is.extra oil in the line.
 
Okay, I get it, thanks for clarifying.
To think that Kiwi claims it still won't fire after even a 1 1/2 hour rest, (see initial post), don't you think it would have cooled enough to spark once again?
 
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