2001 Mercury 90HP four stroke carb model.

This motor is giving me fits!!! It's a little tough starting cold, but some warm starts are enough to drive a man to drink. Actually it's not always the restart itself, but the engine quitting once you open the throttle and take off. Typical scenario is you make a run to the fishing grounds and the motor runs perfect! Shut her down and then make a long drift. Normally it will start right up, then you can put the hammer down and take off. Maybe 5 seconds later the motor just quits! Go back to the primer bulb, and it's flat. Even after pumping it up it can be a devil to restart. I sometimes have to open the throttle all the way. That kinda doesn't make sense as you would think it was flooded, but how can that be when the engine quits and the bulb is flat? You can start this motor and run all day and it won't hiccup or anything, runs perfect. But shut it down for a drift and then it acts up. I've had the fuel pickup out of the tank to check it, new fuel hoses between the tank and splashwell. New hoses to the the 2nd new primer bulb, and new hoses to the fuel pumps. I'm beside myself trying to figure this one out. Thanks for any help suggested!

If the bulb collapses there is a blockage downstream---------------------HOSE/ TANK VENT / TANK STRAINER / TANK PICK-UP TUBE.

That's the logical explanation, but it's doesn't seem to be the case. If there was a problem at one of the points you mentioned, why can I run it at 5000 RPM's all day and it won't skip a beat? Another point I'll mention. After having these problems, I mounted my 9.9 as insurance to get back. LOL. Anyhow I set the fuel delivery up to the kicker by a Tee after the bulb, and a line feeding each engine with a shut off valve for each line. If I run to my spot, and shut the fuel off to my 90, the bulb will stay firm. It baffles me as to why it seems to run out of gas after a shut down, but you go out for a cruise, it will run all day and never quit. I seriously doubt it could be vapor lock, today was 50 degrees and the water temp was 49. I'm thinking fuel pumps, there's two of them. $150 each for a new pump, or $100 for just the diaphragm. They aren't leaking fuel into the crankcase, so that's not an issue. But there is a second diaphragm on the outside cover plate. This diaphragm covers the inlet and outlet of the pump. I'm wondering if there could be an air leak between the 2 chambers which is allowing it to lose prime over time, but when running, the fuel pressure can keep up?

Does the bulb collapse or is it " empty " when this happens.

It's empty! I shouldn't have said it was flat. A couple squeezes and she fills right up.

I've been concentrating on a fuel issue, but maybe I need to look elsewhere. here's a copy of my latest post on the hulltruth. Anybody have an opinion?

I've been having problem with my 2001 Merc 90HP four stroke during warm start ups. I'll make a run to the fishing area, then shut down for a drift. Say 30 minutes or so later when I try a restart, the engine is very hard to start. Usually need to keep the throttle wide open. As the day wears on, it gets progressively harder to start. The engine runs excellent otherwise, and I just had it tuned and checked over at a dealership. Everything seemed to be within specs or was corrected to specs. Reading the Merc shop manual, it states the CDI unit has 3 modes, start up, timing fixed at 10 degrees till it starts and exceeds 600 RPM's. Warm up mode, timing fixed at 10 degrees, and the engine will run at a high idle for different lengths of time depending on temperature. The third mode is normal operation, and the timing can vary between 5 degrees ATDC and 25 degrees BTDC.
The engine starts immediately when cold, but you have to nurse it to keep it running. It doesn't seem to go into the high idle mode. The fuel enrichment devices and the thermosensor were all checked at the dealership. Since I've gone completely over my fuel system including cleaning the carbs twice, once ultrasonically, new needles and seats, float settings and removed the plugs on the idle jets and made sure everything was clean there. I'm wondering if my problems are with the CDI box. Since it controls the timing of the motor, perhaps my problems are with it. I know on a auto point distributer type engine, advancing and retarding the timing affects engine RPM's, and of course how easy it starts. Since I'm not seeing the increase in RPM's which should happen on cold starts, I'm wondering if my CDI modes for start up and warm up are frigged up. Once the engine starts, it runs perfect, but then the CDI is in the normal mode.

Update. Did a timing check on the motor during warm up. timing was at 2 degrees after top dead center, instead of 10 before as the manual calls for. There's no mechanical means to change the timing, so I ordered the CDI. That cured the problem! Old CDI worked perfect once the motor was running, but the start and warm up mode were toast I guess. Funny it would always start cold although you had to nurse it thru warm up. But hot starts were a real devil to get it going. I guess retarded timing on a hot engine has a greater negative effect than on a cold engine.

Thanks for the update-----------------I guess this comes along with the public wanting -----" turn the key starts "----------you have to pay for this technology sooner or later.