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Motors runs for a second and won't keep going.

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schreck421

Member
I have a 2002 90TLR 2 Stroke Yamaha Outboard. It ran very well last year. This year, not so much.

Took it out a month ago. It didn't want to start so I gave it a bit of starter fluid to get the fuel flow going. I know, not exactly ideal but I couldn't seem to get the primer to get fuel to it.

It idled fine and mid speeds fine. When I tried going WOT it would go for a few seconds and then just shut down almost instantly. It has never done that before. So the fuel flow didn't seem to be right. I took the water separator off, drained it, refilled it fresh gas. No water was in it when I took it off. Checked the fuel line with the bulb, it pumps fuel just fine when I took it off. Couldn't find any problems, hooked it all back up. Boat fires up easily which had not been the case so far this year. Was hoping I did something to fix it but wasn't sure what.

Took it out a week later to test to see if it can go WOT. It did just fine for quite a while. WOT worked pretty good. Not perfect but close to last year. We were just cruising around. I tested reverse to make sure that still was ok, it worked. Went forward for a bit. Not long after, it suddenly didn't feel right and shut down. It would start but can only run for a second then dies. Had to be towed back in. Still looks like a sheen of either oil or gas coming out of the prop. I don't remember ever seeing that in the past.

Started troubleshooting. Started with new spark plugs. No change. Did compression check. This boat has had similar numbers in the past, 120/110/100. They're not great but they were like that last year too, the engine isn't exactly new and hoping it will last as long as possible. Really hoping that those numbers aren't enough to say goodbye to the engine.

Bypassed the water separator and my normal fuel tank, just plugged the line into a gas can. If I pump a few times before I start the motor fires up strong for a second or two and then just stalls out. I've found that if I put it in neutral and rev it up quickly it will rev up and I can keep it running that way. Once I go back to near idle it dies instantly. I tried pumping the bulb to keep the fuel flow going to the engine but that didn't do anything, still dies. Fuel filter, fuel pump are both relatively new.

I'm hesitant to mess with the carbs since they were running fine not long before.

I'm stuck... any suggestions would be much appreciated.
 
Fuel starvation. Sounds like it's gonna be you and the fuel system are gonna be bros soon. First suspect area will be any fuel filters, the fuel pump, then the carb float chambers. An 02 might not have alcohol resistant fuel lines and carb components, which can break down if ethanol fuels are used.
 
Is it possible that the carbs could have worked for a while, then some gunk that was in the chamber or something finally broke free and got into one of the jets? I've cleaned them so many times in the past chasing problems and when I get into them I never find anything obvious, they look clean. I use seafoam occasionally to try to keep ahead of it, but yes I use the normal fuel with ethanol too.

Next step, I'll check the filter and fuel pump. When I check the fuel filter I could just bypass it on a try to make sure it's not it.

I had already bought a $75 fuel line with the fuel bulb but my last one SEEMS to be fine so I was going to take it back. I wonder if it could still be bad even if it pumps fuel through it fine (from what I can tell). Considering I tried pumping it while it started it and it made no difference, I wouldn't think it is that.

Thanks for the reply!
 
I MIGHT have found it. Wanted to run it past you.

I took the filter out, then unscrewed the two bolts on the fuel pump that mount it to the rest of the motor. I connected the fuel lines for a test bypassing the filter. When I squeezed the bulb, fuel poured out of the hole where a screw was. I didn't expect that. On closer inspection, there are remains of some black padding that went in between the fuel pump and motor, but there's basically nothing left. I didn't expect fuel come out of that hole. I remembered I still have a backup fuel pump that I replaced while chasing a different problem. So I installed it. Same thing. I know fuel goes through the two lines, but what about those 3 holes. 2 for screws, and one in the middle. Should this happen? Is that by design? If it is then maybe I can replace those 3 things of padding in between the motor and fuel pump?
 
Looking more at things... That "padding" I talked about before is supposed to be a one piece gasket. Mine is gone, just gone. Obviously need to get one. Maybe explains why I have seen a sheen in the water, why the engine bogs down.
 
I’m assuming that middle hole on the fuel pump is for air pressure coming from one of the pistons? That’s makes sense. Still didn’t spect gas to come out where the bolts are.
 
o2batsea said:
Fuel starvation. Sounds like it's gonna be you and the fuel system are gonna be bros soon. First suspect area will be any fuel filters, the fuel pump, then the carb float chambers. An 02 might not have alcohol resistant fuel lines and carb components, which can break down if ethanol fuels are used.
Click to expand...

Replaced the gasket between the fuel pump and wall. Still runs the same, as in, if I prime it up it runs normal for about 2-3 seconds and then starves.” And quits.

I’ve taken out the water separator, fuel filter. Running straight to a portable gas can. Host tested and seems to pump fuel find, but maybe I didn’t test it the right way? I just pumped fuel from a can right back into the can. Fuel sprayed through fine.

Only thing I can think to do now is clean all 3 carbs. Is there any way to test and discover if the which ones are clogged? I was able to unscrew the bolt on the side of the top 2, gas poured out of them. 3rd one is down where I can’t get to.
 
schreck421 said:
Is it possible that the carbs could have worked for a while, then some gunk that was in the chamber or something finally broke free and got into one of the jets?
Click to expand...

Absolutely possible, yes. Replace the fuel pump...it should not be leaking. I'm surprised you didn't smell a strong fuel odor from the cowling....fuel must have been accumulating in the lower cowling pan.
 
OliviaParcker said:
Try to replace the fuel pump ... it shouldn't leak, I repeat. the comment above is really helpful
Click to expand...

I didn’t notice this reply until now. In the meantime I had someone else say that the pump does leak if not clamped down so I didn’t replace it. I took the carbs off, took them apart, dipped them in chem dip, put them back together.

found that someone put the wrong kind of hose and clamps on the middle carb. Was corroded and looked awful. I replaced them with oem parts.

got It all back together. Idles great, but still doesn’t run like last year. Only gets up to 3700 wot, last year was 4200-5000. After running wot, it did die. It’s weird because after it dies, the boat acts as if the battery was dead. Barely had any life trying to start it. Thought I was stranded. After a couple minutes the boat starts right up. Drove it home at medium speed no problem. I still see more sheen of something in the water.

I’m hesitant to replace the fuel pump since all 3 that I had access to leaked if they weren’t clamped down to the motor, but I’ll see if I can buy a new one tomorrow at the store if they have one. Maybe the fuel pump leaking can’t keep up at wot and it’s leaking gas into the motor where it gets it’s vacuum, and that’s what I’m seeing come out the exhaust?
 
For anyone still following this thread. Not sure why but we replaced the fuel pump. Still wasn’t the problem.

went back and did a compression check again. Now it’s bad. 120/90/35

I’m praying for a miracle at this point. All I can think to do at this point is to take the head off and see if I can tell what’s going on.
 
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