5 hp 4 stroke

I have a 5hp 4stroke for my dinghy, it dies out at half throttle and up. It will restart and idle, but will die again on half throttle. Is the fuel pump bad? Filter is clear. thanks

A little history would help, Serial #,How long have you owned it? Did problem just start,Was it progressively getting worse ?Old fuel in tank? New fuel added to old fuel? While running pump primer bulb constantly, If condition improves there's a restriction in fuel delivery system or a defective fuel pump

It started first use this summer. a little old fuel in tank but about 1/2 gallon. Topped it off with fresh. Squeezing the bulb helped, but did not allow higher rpm, just kept it from dying, longer. I removed the carb, disassembled and found nothing wrong. Reassembled. Still same issue. Don't have the motor here for the serial #. 2004 vintage.

OK, you have a Tohatsu MFS4/5/6 A2 or B. They have very reliable fuel pumps. If you want to check for pump delivery, wait until the motor stalls, and then open the carb drain. If only a couple of drops come out, you are not getting enough gas to the bowl. OTOH, if you get an ounce or more of gas, you are getting enough fuel in the bowl. The same pump is used on the 8/9.8, so it is more robust than actually needed for the 4/5/6.

There are a few things to check:
1- Oil level (must be between the hash marks on the stick -- you must screw-in the stick until it bottoms to get a reading. If you just put it in with screwing in down, you will get a reading lower than actual. If the oil is high, you will get high crankcase pressures, which can cause stalling and many other issues.
2- Float height (the float needs to sit parallel to the carb casting when you have the carb inverted.
3- Apparently you have the external tank setup (or possibly the dual-tank). If you have dual-tank, and want to use the external tank, you must shut off the internal tank, or it will drain out by gravity, and you will suck air from the integral tank.
4- The obvious things to check are that the fuel hose o-rings are good, and the vent is open. And of course you must have a good spark plug.

The bad news is that all EPA-rated motors have very lean carbs, and even slight varnishing in the small passages will cause the mixtures to be much too lean. You cannot clean these carbs with carb spray alone, and Never with any sort of wire or probe.

In 95% of these cases, the carb was allowed to sit for a week or more with gas in it. You must always empty the carb, either by running dry, or by opening the drain screw at the end of each and every day. If that's the case, You can probably remove the carb, completely disassemble it (including jets and emulsion tube nozzle), and soak all non-rubber parts in real carb dip, available from auto parts houses, for at least 4 hours at room temperature, and then blow out with liberal amounts of generic acetone-based carb spray, then reassemble, carefully checking float height (which is almost always good). If there is a loose bit o crud in a passage, it could move around like a marble in a game, and get sucked against a passage at higher flow rates, blocking flow. That is more often seen in brand new motors, and in that case, can be a tiny bit of machining debris that made it into the fuel system.

If the carb is too lean, and you are unable to clean it correctly, you can buy a carb for the MFS6A2, and end up with 20% more power.