Exhausted with T50tlru

[buck_higgins]

So I’ve been working on this Yamaha 50 horse four stroke for a little while though But I just can’t seem to make any headway. Runs rough at idle, sometimes has starting issues and loses power under load. Also stalls out when you throttle to quick. So far I’ve checked the spark replace the spark plugs and replace the coil‘s. Compression test is even with 186 psi almost exactly across or all four cylinders. I have also stripped the carbs and clean them out and reassembled. On my four gauge sink tool they all look fairly even. I have also eliminated fuel as an issue By running a new line to a portable gas can with new gas in it. Also tested the fuel pressure. The two outlets were not the same. Top outlet was 3psi idle and 4-6psi revving. Bottoms fuel outlet was 1.5-2.5psi idle and 3psi revving. I believe being carbed it’s a low pressure pump.

None of these seem to have fix the problem. Any suggestions?

[TownsendsFJR1300]

Don't know the year engine but it sounds like possibly a bad fuel pump.

[99yam40]

good compression, good spark, correct timing, and proper fuel to air ratio are what is needed for the motor to run properly.
compression, spark and timing are all easy to check.
proper fuel to air ratio is not that easy.

most of the time it is carbs not being as clean as they are though to be

[buck_higgins]

Seems to be working well on the trailer finally. My spray with carb cleaner cleaning job helped but didn’t fix it. Fuel pump helped but didn’t fix it. Today I stripped the carbs down again and did an ultrasonic clean with simple green. Might not be running totally perfect but it’s damn close. Smooth idle and no hesitation when revving. Can’t wait to get out there on a test ride.