1994 Yamaha Pro-V VMax 150 hp warning alarm

[Dr. David A. Johnson]

My 1994 Yamaha Pro-V VMax 150 hp outboard warning alarm activates when the motor is idling after running hard at 5500 RPM. The outboard starts well and runs fine at top end. However, after running at top end, if the engine stays at idle for 15-20 minutes, the warning alarm sounds. I brought the outboard to a Yamaha Certified Marina and the technician ran the motor in the tank for over three hours and could not make the alarm sound nor find the problem. He said that engine temperatures were all normal on all six cylinders and that the engine ran fine. He thought that perhaps some weeds had gotten sucked in to the engine and plugged up the water flow. Today, after putting my boat in the water and running it hard for 15 minutes, I began running the engine at idle. After about 15-20 minutes at idle, the warning alarm sounded. I immediately turned off the engine. After waiting about 5 minutes, I restarted the engine, but the alarm came back on. After waiting for another 15 minutes, I restarted the engine and it ran fine, no alarm. I ran the boat up to 5600 RPM and it responded fine, no problem. Then, I slowed to idle again. After about 15 minutes, the warning alarm sounded again. So, rather than turn off the engine, I attempted to accelerate, but the engine wouldn't run above about 2500 RPM, so I then turned off the engine. After waiting about 15 minutes, I restarted the engine and it ran fine and I accelerated to 5600 RPM. At that point, I put the boat back on the trailer. The water temperature was 37 degrees F and the air temperature was 38 degrees F. I've not had any previous problems with my Yamaha, and have it serviced per schedule. I have recently had the waterpump impeller replaced and water pumps out the "pee hole" with a normal stream. This is frustrating. Any suggestions other than "don't run at idle" are appreciated. Thanks in advance for your help.

 

[rodbolt]

Re: 1994 Yamaha Pro-V VMax 150 hp warning alarm

have the thermostats been replaced and the pressure control valve serviced ? next time it does it immediately shut down, remove the hood, dissconect both pink wires at the cyl heads. turn the key back to on. hook up one pink lead at a time to figgure out which bank is heating up.<br />but if the stats and pressure valve have not had recent service that is where i would start

 

[Dr. David A. Johnson]

Re: 1994 Yamaha Pro-V VMax 150 hp warning alarm

Thanks, Rodbolt. According to my Yamaha service technician, the thermostats and pressure valve were functioning properly and didn't need replacement. Any additional thoughts?