motor problems - what do you think?

[fisher]

Took the boat to Simcoe for a spin yesterday to make sure all is working well.

 

Started up the motor and it sounded good. Put it in gear and slowly increased the speed every few minutes going faster and faster each time. All was well until I hit top speed when after about 10 seconds, the motor shuts down completely.

 

Started it up again and same thing - quits at top end but runs fine at lower speeds. After two more times quitting at top end, I decide to call it the day before I get stranded on the lake. On the way home I dropped it off at the marina I deal with.

 

Based on my description of events, they suspect a number of things could cause the problem:

 

- bad tank

- bad hose (bulb)

- fuel issue (water in the fuel)

- activator?? (not sure if I heard right or what that is)

 

They ruled out old gas since I emptied the tank last fall and just filled up earlier that day from Shell.

 

They are busy so it may take some time to look at it. What do you guys think? Any ideas?

Edited April 19, 2009 by fisher

[HTHM]

Check your fuel lines, they may be leaking or cracked and air is getting in the system.

[Bernie]

Did you open the vent on the fuel cap?

Sounds like a fuel starvation issue.

[fishboy]

What type of connector to the tank/motor? I can remember having an OMC with a simple o-ring problem

Edited April 19, 2009 by fishboy

[River Rat]

all of the above are places to start....if its carbed, there are rubber membranes that pump fuel and can stretch from pressure (closed air sytem)

 

RR

[fisher]

Thanks for all the replies.

 

The vent was open in the tank.

 

If it was a fuel line problem (ie. bulb, etc..) would it not cause an issue while at the lower speeds as well? I was having issues only at the highest speed.

 

As for the connector, I am not sure what you call it but, it has a clip that connects the fuel line from the tank to the motor. And there is a long thin metal adapter that connects the line to the tank (you twist it slightly to keep it in place)

[Bernie]

If it was a fuel line problem (ie. bulb, etc..) would it not cause an issue while at the lower speeds as well? I was having issues only at the highest speed.

When you are at full throttle it is using more fuel. Once the fuel in the float bowl is used up it will quit. If the fuel flow is restricted but not completely blocked it may run fine at lower throttle position. A fuel pump could be the problem as well as dirt in a fitting. Verify the vent is functioning too. I will sometimes loosen the fuel cap if I suspect a venting problem. Seen this happen in cars too.

[fisher]

Thanks Bernie...that makes sense.

[smokin joe]

When you are at full throttle it is using more fuel. Once the fuel in the float bowl is used up it will quit. If the fuel flow is restricted but not completely blocked it may run fine at lower throttle position. A fuel pump could be the problem as well as dirt in a fitting. Verify the vent is functioning too. I will sometimes loosen the fuel cap if I suspect a venting problem. Seen this happen in cars too.

 

 

Great point Bernie.

[fisher]

Update...

 

Spoke to the Marina and they said there is low compression from one of the pistons. !? I just rebuilt the motor with them last year ...

 

They did say that they will warrant their work and that their plan is to open up the motor in the next few days to see what is happening. That made me feel somewhat good ...

 

I forgot to ask him if he thought the low compression would cause the motor to stall at top end. Oh well, I guess I'll wait to see what he says.

 

Anyone think the low compression on one piston would cause the motor to stall at top end?

[GEO]

yes that is what happened to me .bought a boat off my wifes uncle ran fine.

When you got on the gas it quit. had to rebuild it low compression.At least they are taking care of it.

[JohnAB]

On a 2 stroke, low compression can cause the exact problem you are describing. As the motor has to suck the fuel up from the crankcase and make the reeds work, a poor seal (compression) would greatly reduce its ability to get enuff fuel into the crankcase and into the cylinder to run at full throttle for any length of time. Hope that makes sense as that is my understanding of it.

Edited April 24, 2009 by JohnAB