I have a fuel problem

[FishStretcher]

I had this same phenomenon. But I could see the squeeze bulb getting sucked flat. If yours isn't, then it is after the squeeze bulb. (Probably the outboard) Mine was a tank that had a straight cut tank pickup just off the bottom of the tank. It wasn't slash cut. It would suck itself flat to the bottom of the tank at full throttle.

My 4 stroke yamaha has inline filters, one per carb float bowl. They are tiny and plug easily- they are the diameter of a 6mm/ 1/4" hose in the float bowl, pinned against the engine block. Those will plug if the rest of the system isn't clean. but a 2 stroke might not have this "feature".

[Bushwacker]

Don't run it long or hard if you think it's running lean, as that's a quick way to overheat pistons, and if you're running premix you're also starving the motor for oil! I'd suggest you duplicate BRP's fuel system test, i.e., in the line between the filter and engine, install a section of clear vinyl tubing with a vacuum gage tee'd into it. When you run the motor, look for bubbles in the clear line from an air leak, and monitor the vacuum gage @ WOT to see how much restriction you have between tank and engine. The limit they use is 5"Hg, but lower is better. Each 90 degree elbow in the system is typically worth about 0.5" Hg pressure loss, but I've also heard of 3/8" elbows that weren't drilled out properly, so they were only 1/4" inside, so that would also cause significant restriction. If you get a high reading indicating a blockage in the pickup tube try blowing back thru the line with a high pressure air hose. Also make sure tank vent isn't plugged up with wasp nests, etc. Maybe try running off a portable tank to confirm problem is in fuel tank.

[wattaway2]

Sent ya a pm

[eggsuckindog]

Isolate and Eliminate - move systematically thru the system 1 item at a time, verify that is working and go to the next item. Doing the extra tank does eliminate the entire tank and filter, then you know further in. The carbs will have a drain screw in the bottom but I doubt that all of them are plugged up but draining will get any crap in the bottom out, squeezing the bulb will flush the whole system - the diaphram fuel pump is a good candidate and a rebuild kit is a minimal cost, check everything along the road, starting at the tank - filter - connector - and just keep going it has to be there someplace

If its a carbed motor with just a diaphram pump it can be bypassed by squeezing the bulb, at least that works on Rudes, although a new diaphram probably wouldn't hurt, should be a DIY job

[shine]

anti siphon valve might be problem. I have had to remove a couple of them on different boat in order to get adequate fuel flow. You can push the ball and spring out with a screw driver, then test to see if that solves the problem. If not, then I would replace it with another one (not expensive) as they are a nice thing to have (required ).

I have had 2 strokes that just pulled gas too fast (drank gas) and would close of the valve. Also, a newer yamaha 4 stroke has a low pressure fuel pump that turns on intermittently at low RPMs (becasue it doesn't pull enough gas at idle), when that pump woudl kick on it woudl lock up the anti siphon valve

[jorgeinmiami]

Well I'm home now and I started to go thru it to see what is the problem

Vent line is ok with nothing restricting it
took apart fuel pump and diaphragm looks good
changed the small filter under the cowl
took out the plugs on the carb bowls to see what came out and it looked clean
took some carb cleaner spray and cleaned out the carbs when I took them apart and the insides looked clean, spayed it into every little nook and cranny and into any thing that looked that it could clog and put back together.

replaced all the "zip ties" with SS clamps on the gas lines under the cowl.

The engine fires right up and runs in idle with no problems

I am going to go with an Aux tank to see if it is something in the tank sometime this weekend

All that remains is the pickup in the tank, which involves undoing the console then the tank cover and putting it all back........something that I really do not want to do in the Florida heat and humidity

[Blue197320]

Jorge we can test it in the canal to see how it runs if you don't want to deal with the ramp and pay the fee.

[WildBill]

George, while your at it drain some of the fuel from the fuel line to the motor, maybe a 1/2 gallon or so into a oil pan or some thing like it about 6-8 inches deep and look at it and watch it in direct sunlight. I have seen the separation before and delamination of the fuel lines (black film)in the fuel. I experienced the same identical symtems on my 250 merc a couple years back. It clogged eveything up and I had to rework everything including cleaning the tank.

goodluck bill

[Runco]

Check for screen filter at the top of your pick up tube. Stupid place for a filter but my 1985 had one and so did a friends boat have one. Took me a long time to find it.

[Blue_Heron]

Jorge,
If the ball isn't being sucked flat, the problem is in the motor.

I know you've already been in the carbs, but...

I had the identical problem on my Merc Carb 200 and it turned out to be the float valve on one of the carbs. The valve seat had unscrewed a little, so the valve was shutting before the bowl was full. It would run fine at idle, but would starve two cylinders when you opened it up. To check, you should be able to turn the bowl upside down, and the float will be flush with the top of the bowl, assuming yours is the same as the carbs on the 91 through 96 Mercs.

There's another check you can do if you've got the boat in the water. When it starts to bog, hit the enrichener (choke). If it picks up more rpm, the problem is in the middle or bottom carb.

The only other thing I can think of is electrical. Some of the V6 Mercs have a dual stage stator. It uses two sets of coils, one to produce spark below 3000 rpm and the other for over 3000 rpm, if memory serves. This is what I thought was wrong with mine when I figured out it was a fuel issue.

Good luck,
Dave