mrmamiller
Petty Officer 2nd Class
- Joined
- Mar 7, 2011
- Messages
- 167
I know I'll get blasted for not providing enough information or not reading the manuals, but here goes anyway...
I bought a used boat. Motor is a 2003 90 HP Yamaha, 2 stroke, carbureted. The motor ran fine on my test drive, prior to buying. BUT, at the RPM's that it was test drove, there was no problem. Today was my first time out with the boat, and I had problems. Symptoms: At 600 RPM in gear, motor overheat alarms within 3 minutes. At idle (800 RPM), no problem. At 900-1300 RPM in gear and running, no problem. 4000 RPM for 5 minutes, alarm. Water peeing.
I have measured temps with an IR temp gun, and in fact, it is overheating. The temps around the heads appear to be uniform and jive with the temp around the thermostat. There is a pee stream, but it is weak compared to my 110 Johnson. The temps after alarm and shutdown indicate the temp is about 185 degrees. When the temp returns below 145, the alarm is silent when turning on the key. After an overheat event, running the motor at 1000 RPM brings the temp down nicely (from 145 down to 125 or so). So, my assessment is that it doesn't **** really low RPM or really high RPM.
I spoke with a mechanic who used to service this motor. The "water pump impeller, gaskets, plate and cup" were replaced 3 months ago, and the boat has really not been used since. That mechanic suggested the thermostat and poppet valve as being the likely culprits. He also mentioned that when removing the thermostat housing, be sure to warm the engine first, and be real careful trying to loosen the bolts, especially the lower two bolts, as they can be seized (and snap off). This is a saltwater motor.
So, I am in Florida, not at my usual home with all the tools in the world, and no Yami manuals yet. I would like your collective take on what is going on. Thanks for your valued input, Mark
I bought a used boat. Motor is a 2003 90 HP Yamaha, 2 stroke, carbureted. The motor ran fine on my test drive, prior to buying. BUT, at the RPM's that it was test drove, there was no problem. Today was my first time out with the boat, and I had problems. Symptoms: At 600 RPM in gear, motor overheat alarms within 3 minutes. At idle (800 RPM), no problem. At 900-1300 RPM in gear and running, no problem. 4000 RPM for 5 minutes, alarm. Water peeing.
I have measured temps with an IR temp gun, and in fact, it is overheating. The temps around the heads appear to be uniform and jive with the temp around the thermostat. There is a pee stream, but it is weak compared to my 110 Johnson. The temps after alarm and shutdown indicate the temp is about 185 degrees. When the temp returns below 145, the alarm is silent when turning on the key. After an overheat event, running the motor at 1000 RPM brings the temp down nicely (from 145 down to 125 or so). So, my assessment is that it doesn't **** really low RPM or really high RPM.
I spoke with a mechanic who used to service this motor. The "water pump impeller, gaskets, plate and cup" were replaced 3 months ago, and the boat has really not been used since. That mechanic suggested the thermostat and poppet valve as being the likely culprits. He also mentioned that when removing the thermostat housing, be sure to warm the engine first, and be real careful trying to loosen the bolts, especially the lower two bolts, as they can be seized (and snap off). This is a saltwater motor.
So, I am in Florida, not at my usual home with all the tools in the world, and no Yami manuals yet. I would like your collective take on what is going on. Thanks for your valued input, Mark