yamaha fuel management problem - The Hull Truth

RonG · 07-02-2008, 07:37 AM

I have 1999 150 hp motors that run great (but are thirsty). I lost the gph reading from the starbord motor and traced the problem to a crimp on the black ground wire from the sensor plug. Fixed that and got reading back. Now I lost it again. Checked from plug to battery ground ok. Can sensor be checked? repaired? disassembled and cleaned? or does it have to be replace? Thanks Ronny

A1 Outboard · 07-02-2008, 08:23 PM

The easiest way to test the sensor is to attach it to the other engine, in other words, swap them to see if the problem follows the sender.

RonG · 07-03-2008, 07:41 PM

Well I went out to swap the wires today. I started them first and BOTH worked. I found however they were kind of erratic at staying on. They would drop out at idle and I would have to go up to about 2500 to start them again. Really tempted to take one apart. Seems like something is getting stuck! Thanks Ronny

A1 Outboard · 07-04-2008, 03:02 PM

If you have the original Yamaha fuel flow senders, you may get them replaced under a recall that they had some years ago. I don't have the information handy, but there was a design change after there were reports of leakage, which is a safety hazard. See an authorized Yamaha dealer and see if the senders are the old style that should be replaced.

RonG · 07-05-2008, 02:31 PM

Senders were replaced already under recall. Did you ever take one apart? Thanks Ronny

A1 Outboard · 07-05-2008, 02:35 PM

Nope, sorry but I can't help in that department

RonG · 08-10-2008, 03:51 PM

Ok I Took the starboard sensor off and checked it out. I noticed the UP arrow pointed DOWN. (factory installed) I put it in right and changed the 10 micron filters. Did the same with port side. Took it out for a ride and port motor quits only at high rpm (4500+) like it's starving for fuel. If I throttle back real fast it wont stall. I looked at the filter on the engine and it looked clean. I got rained out before I could take it off and dump it. Motors ran great the day before!!! Any ideas??? Thanks Ronny

P.S. Motor runs at high rpm just fine for about 30 seconds before it quits.

A1 Outboard · 08-12-2008, 03:42 PM

If you think it is starving for fuel, hook up a pressure gauge after the fuel pump and monitor it while running. Also temporarily hook up a vacuum gauge and a piece of clear fuel line on the inlet fitting of a pump. Look for vacuum readings above 4" Hg and for air bubblles in the clear line. IF any show up, the fuel system has to be repaired.

RonG · 08-12-2008, 07:15 PM

Thanks for the reply. Tonight before I read your post I thought I might of had a small crack in the sensor casting pulling in air so I took it out and went direct from the filter. I also removed and replaced the filter element on the motor. Same problem. I am not so sure it is a fuel problem. It runs strong to 4500-4700 rpms, push it to 5000 and in a few seconds it's like you shut the key OFF!!! Could this be electrical??? Thanks AGAIN Ronny