Engine died in full throttle, now won't start

[Robp722]

1966 Johnson 9.5, Model MQ-12A(even though it looks to be MO-12A). This motor was running great a week ago. I was on the river Sunday and at full throttle the motor sputtered and stalled. The bulb was still firm, I cranked it up and it ran for about 30 seconds then stalled again. I thought it was a fuel issue. The buld is firm, cleaned the fuel screen and fuel pump. Took the carb off, cleaned all the jets and made sure everything was working properly. I cranked it yesterday and it fired but would die within seconds. This morning I couldn't even get it to turn over. What is the problem?

 

[Cofe]

Re: Engine died in full throttle, now won't start

Some things happen, because of what we might have forgotten to do.

From the sound of things, did you happen to forget to mix oil in the gas?

 

[Tim Frank]

Re: Engine died in full throttle, now won't start

1966 Johnson 9.5, Model MQ-12A(even though it looks to be MO-12A). This motor was running great a week ago. I was on the river Sunday and at full throttle the motor sputtered and stalled. The bulb was still firm, I cranked it up and it ran for about 30 seconds then stalled again. I thought it was a fuel issue. The buld is firm, cleaned the fuel screen and fuel pump. Took the carb off, cleaned all the jets and made sure everything was working properly. I cranked it yesterday and it fired but would die within seconds. This morning I couldn't even get it to turn over. What is the problem?

If it won't even turn over, it may have overheated or as suggested, lack of oil.
You need to free it up and check compression.

 

[Robp722]

Re: Engine died in full throttle, now won't start

It's not from a lack of oil. Actualy, I'm about an ounce over 50:1

 

[Cofe]

Re: Engine died in full throttle, now won't start

Ok like Tim said, probably an overheat. Check thermostat, waterpump output. Work on getting it freed up.

 

[Robp722]

Re: Engine died in full throttle, now won't start

ok, thanks

 

[scrampbell]

Re: Engine died in full throttle, now won't start

Did you check for pee when you got it started back up out on the river? Or did you take the cover off and notice it was really hot when it died? Did you try to turn the flywheel by hand during any of this? Or notice that it was harder to pull during any restarts?

Just to clarify... by "couldn't get it to turn over" do you mean that it's physically seized and impossible to pull? Or do you mean something else?

If it's seized, then getting it unseized is your first task and for that let me recommend PB Blaster. Spray some in through the spark plug port and let it sit for a few minutes and try to work the fly wheel back and forth until it breaks free. You'll probably need a big-a** wrench. Good luck.

 

[Tim Frank]

Re: Engine died in full throttle, now won't start

It's not from a lack of oil. Actually, I'm about an ounce over 50:1

Not doubting you, but that is an odd way of measuring....how do you mix your gas?

 

[Robp722]

Re: Engine died in full throttle, now won't start

I have a gallons to ounce mix ratio downloaded on my phone. By not turning over I do not mean it is seized, I mean when I pull it there is no ignition. I can pull it, without any added resistence to the pull chord. After it died on the river I pulled it off and put it in a barrel. I got it to run fine in the barrel but I only ran it for a minute or two. The water is circulating through the motor normally, which on these motors is not a stream but it spits the water out. I don't think the engine has a heat issue.

 

[scrampbell]

Re: Engine died in full throttle, now won't start

Hmmmm.... I'm ruling out the carb for now since you gave that the once over. Check for spark just to rule that out. For now, I'm leaning to trouble somewhere in your fuel line. Fact that you could get it started, but that it dies within seconds says to me that you can prime it just fine (and that your spark is okay -- currently inability to start at all is worrisome), but there's a bug in the system of supplying fuel to the carb under normal running. Could be your fuel pump or could be getting air introduced in the line somewhere along the way.

To check the fuel pump.... disconnect the line leading from the pump to the carb and make sure fuel pulses out when you try to start it.

If pump checks out then closely inspect your line between pump and carb. Are there any plastic fittings or cracked line? Plastic fittings may crack at the base and introduce air. Obviously, cracked line would do the same. Let us know....

 

[Robp722]

Re: Engine died in full throttle, now won't start

To check the fuel pump.... disconnect the line leading from the pump to the carb and make sure fuel pulses out when you try to start it.

I'm confused on this one. I have disconnected the fuel line going into the carb and squeezed the bulb. It has a contant flow of premix from through the gas lines, fuel pump and carb. I have gone as far as pulling the drain plug on the carb to make sure I'm getting flow through the carb to that point. If I pull start with the fuel line unattatched where will fuel come from?

 

[Robp722]

Re: Engine died in full throttle, now won't start

I went to a local dealer today and bought a carb rebuild kit. Although I rebuilt my carb recently, this kit comes with new cork seals for the fuel pump. I cant even begin to understand how a fuel pump could go bad on this engine. It's just a piece of plastic with a metal reed screwed into it. It's about as basic as I've seen.

 

[scrampbell]

Re: Engine died in full throttle, now won't start

When you squeeze the bulb, you're manually pushing fuel through all the lines by creating pressure at the bulb.

When the motor turns, the diaphragm on the fuel pump operates and pulls fuel from the tank and supplies it to the carb. Basically, it takes over from you squeezing the bulb. You want to make sure it's doing its job.

So you want to keep the fuel lines intact between the tank and the fuel pump, but you have to disconnect the line between the pump and the carb so you can verify that it's doing its job (by seeing fuel that would normally be supplied to the carb coming out of the line in pulses). You're not trying to start the motor here, just ruling out the fuel pump.

It probably hasn't gone bad, but it's easy to check and if it is bad, then you'll want to find that out before spending however long tearing apart the carb on a wild goose chase.

 

[Robp722]

Re: Engine died in full throttle, now won't start

I understand now, thanks. I'll check it this evening and let you know.

 

[Tim Frank]

Re: Engine died in full throttle, now won't start

You don't say your history with this motor or boating in general.
Any chance that the tank cap is tightened fully?
That effectively creates a vacuum and the fuel flow will stop.

 

[Robp722]

Re: Engine died in full throttle, now won't start

I've had this boat and motor for about 7 months. I've owned boats for about 13 years off and on and consider myself somewhat savy on 2 cycle engines but some things you don't learn about until it breaks i guess. The gas cap was the first thing I checked and cleaned.

 

[Tim Frank]

Re: Engine died in full throttle, now won't start

Ok...no offense meant, and it would have been nice to find something that simple...if only....

 

[Tim Frank]

Re: Engine died in full throttle, now won't start

I don't think the fuel pump will stop a motor from starting if the float bowl(s) are full...might not run long....but should start.

Try getting a small squeeze bottle or a spray bottle....4 oz. is a good size....put a few ounces of premix ion it and spray a shot nto the carb throat.

See if it fires.
That should rule out spark if it does... and verifies that you have a fuel problem if it doesn't. Other problems may also be there.

 

[Robp722]

Re: Engine died in full throttle, now won't start

ok, thanks

 

[Robp722]

Re: Engine died in full throttle, now won't start

Ok, so I may have not diagnosed the problem but I did get it running, and running very smoothly now. I bought a carb kit and replaced the old float, the fuel filter and the cork seal around the fuel filter. I was getting pre-mix from the fuel pump. I replaced the spark plugs and got it to start. Let it run for 3 or 4 minutes to adjust the slow drive knob and did a compression test, which was near spot on. I let it sit and started it several times; start up on first pull. Oh, and I disconnected the kill button just in case it had shorted out then plugged it back in. I don't know what made the difference but it's running great now...I'm pretty sure thats all that matters! Thanks to everyone for their advice. I do wish these model motors cycled more water through the cooling system.