2003 F90 Runs for 30 Sec and Dies

[snooktarpon]

I purchased a 18' bass boat this summer with 2003 F90TLRB outboard with minimal hours (less than 20). The previous owner just never had time to take it out. The boat and motor has been kept indoors so it's basically in brand new condition.

At the time of purchase, I took it on the water and it was difficult to start. After waiting about 10 minutes thinking it was flooded, it finally started and I ran it on the water for about 30 minutes.

4 months later, I attempted to take it on the water and this is what happened:
- I squeezed the fuel priming bulb numerous times and noticed it was holding any pressure (I could keep squeezing it completely). I can't remember what it was like 4 months ago.
- The motor would start and run at idle for about 30 seconds and then die
- After it died, I could not get it started. I then squeezed the bulb again several times and it didn't help.
- Thinking I might have flooded it again, I would open the throttle to max (in neutral) to clear the cylinders and this still wouldn't help.
- The only thing that would help was to wait about 10 minutes and the engine would start and then die after 30 seconds.
- While in idle, if I tried to give it gas (in neutral or in gear) it would die instantly
- So I replaced the fuel priming bulb with the official Yamaha part
- With the new bulb, it seems like it was holding more pressure but I could still squeeze it completely. If I did a bunch of small quick squeezes, it would hold some pressure.
- The motor with the new bulb started right up but then died again 30 seconds later and I couldn't restart it without waiting (so no change with the new fuel bulb)
- When I had it started again, I squeezed the bulb several times then the motor died instantly
- Again if give it gas when it is in idle, it dies instantly

I'm at a loss trying to figure this out. The closest boat ramp is 50 minutes away so I'm hoping my next repair will solve it. I don't want to fix one thing, then drive out to the ramp only to find out that it still doesn't run.

I'm pretty sure the motor has the original fuel filter so I plan on replacing it. Could this be the issue?

What about the fuel pump? Is there a way to test it?

Any other ideas?

I purchase the Yamaha service manual but it's basically a book of diagrams. There isn't any meaty info on troubleshooting fuel issues. I'm pretty handy. I've torn down my motorcycle (replacing clutch plates, etc.) in the past but I've never worked on outboards before. I would rather do this myself then taking it in to a Yamaha shop.

Thanks in advance for your help.

[boats.net]

Need to remove and clean carbs, probably gummed up from sitting.

[rodbolt17]

your also going to need a 4 channel manometer to resync the carbs.
you will also need to remove the brass tamper proof plugs covering the A/F mixture screws.
takes me about 4 hours to do that engine and I may have seen one or two.

[snooktarpon]

your also going to need a 4 channel manometer to resync the carbs.

Will this manometer work: www.carbtune.com ?

you will also need to remove the brass tamper proof plugs covering the A/F mixture screws.

Are there anything special tools or procedures that I should know when removing the brass plugs?

[snooktarpon]

Another question:
Can I run/test the motor on land while pumping water via a garden hose through the hose adapter?

This would make life a lot easier but I don't want to potentially damage the motor if there are risks.

[rodbolt17]

that carb tune model will work fine.
yes at IDLE only you can run it on the flush port.
I usually lock the carb in a vise,smooth jaw aluminium, and carefully using a 9/32" drill drill a hole in the plug.
then use a #10 self tapping screw and screw it in.
then use a pair of side cutters grab the screw and pop out the plug.
you will most likly allow the drill to go to deep hitting the A/F screw.
black tape around the drill bit will help.
typically a starting point is about 3 turns from ligtly seated.

[snooktarpon]

that carb tune model will work fine.
yes at IDLE only you can run it on the flush port.
I usually lock the carb in a vise,smooth jaw aluminium, and carefully using a 9/32" drill drill a hole in the plug.
then use a #10 self tapping screw and screw it in.
then use a pair of side cutters grab the screw and pop out the plug.
you will most likly allow the drill to go to deep hitting the A/F screw.
black tape around the drill bit will help.
typically a starting point is about 3 turns from ligtly seated.

***, Yamaha doesn't make it easy. So the Yamaha techs have to deal with this too.

Thanks for the info.