Tohatsu 6hp 4 stroke not running at optimum b/c of bad fuel pump??

So I have a 2008 6hp that I use on my porta-bote in the rivers and lakes in the Jacksonville area that seems to have a problem of some sort maintaining fuel throughout the engine. I have a new tank, fuel fittings, line, primer bulb and have removed the fuel line just before entering the fuel pump to make sure adequate fuel is being pumped through it and it seemed to be fine. I reconnect the fuel line to the pump and with the cowling (and engine) off, it sounds like it's filling up correctly however when I have the engine in the water, the primer bulb does not seem to be tight. So far I have checked the fuel tank, lines, fittings, etc to see if there are any leaks and there were none and I have taken apart the carburetor and cleaned thoroughly and reattached but everytime I run the engine, it seems to start up fine, idle and when i put it in gear and throttle up, the primer bulb goes weak. Just today I found out that while under way, I can prime the bulb until it is tight and the engine will not die and I can rev to WOT but obviously I'm looking for a permanent fix for an issue like this. Anyone seen or heard of this problem before?

Re: Tohatsu 6hp 4 stroke not running at optimum b/c of bad fuel pump??

The fuel line is under suction as the fuel is drawn into the motor. Therefore the brimer bulb does not necessarily stay firm while running. If the tank pickup has an obstruction, or the vent is not clear, or if the tank is very low (so the fuel has to be drawn uphill a long way), the primer bulb can collapse. So, the bulb being less than firm is in fact an indication that the fuel pump IS working correctly.

Re: Tohatsu 6hp 4 stroke not running at optimum b/c of bad fuel pump??

pvanv said:

The fuel line is under suction as the fuel is drawn into the motor. Therefore the brimer bulb does not necessarily stay firm while running. If the tank pickup has an obstruction, or the vent is not clear, or if the tank is very low (so the fuel has to be drawn uphill a long way), the primer bulb can collapse. So, the bulb being less than firm is in fact an indication that the fuel pump IS working correctly.

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So there are no obstructions in the fuel tank or lines and the tank itself is in the transom next to the engine, so it's not too low to prevent adequate suction. I'm trying to determine what to try next working my way from the "outside in." With all the aforementioned potential issues addressed, I'm wondering if there is not sufficient suction for some reason.

Re: Tohatsu 6hp 4 stroke not running at optimum b/c of bad fuel pump??

Is your engine still in warranty?

Re: Tohatsu 6hp 4 stroke not running at optimum b/c of bad fuel pump??

No, it was manufactured in Sept. 2007........

Re: Tohatsu 6hp 4 stroke not running at optimum b/c of bad fuel pump??

It may in fact be in warranty. When was it purchased? There is a 3-year warranty from date of purchase -- not manufacturing date.

So what exactly is the malfunction, aside from the primer bulb issue? If the bulb collapses, the fuel pump is pulling fine, and you aren't allowing enough fuel into the line. Period. That could be a poor vent, etc. If it is merely not solid-firm, that's normal, due to the suction in the line.

Is there a problem where you are able to throttle up all the way, run fine, and after a few minutes, the motor slows down (like it's running low on fuel)? If so, that could be some sort of [possible] fuel starvation, especially if you can then pump the primer while this is happening, and have it regain RPM. That could be caused by the fuel filter, fuel pump, incorrectly set float, or a worn needle/seat.

On the other hand, if the situation is that it works OK in neutral, but not in gear under load, that is a completely different symptom, and is likely a fouled/varnished carburetor.