Hey Folks,
I need some help diagnosing a problem with my Yamaha. I got it out of storage after about 2 months not using it, started it to warm it up as usual on muffs at home. No problem.
Once I put it in at the lake I started it, as it idled for about 5 minutes, got the overheating buzzer. Trying to diagnose the overheating problem I have done the following:
1. Bought a Sierra impeller and installed it into the exiting housing. Didn?t help.
2. Took out and cleaned both thermostats, they were pretty gross
3. Cleaned and re-tensioned overpressure valve. This seemed to help, and the boat could idle for 5+ minutes.
In deciding that this was the problem, I ordered new thermostats, new gaskets and new overpressure valve and spring.
The next weekend I:
1. Replaced the thermostats with new, and put on new gaskets
2. Replaced the overpressure valve and painfully (because it was OLD and stuck) it?s gasket
1. Took off the lower unit again, replaced the gasket under the water pump as well as it?s gasket.
I started the engine with muffs and it proceeded to overheat in under 2 minutes!! Being convinced I screwed something up I took it all back apart, checked everything, put it back together, same result. The pump did have a tough time priming initially, so being convinced that maybe the Sierra impeller I got was bad.
I went and got a replacement pump kit from a local boat dealer and replaced the housing, casing, both seals, gasket, plate, bolts, impeller and shim - all with genuine Yamaha parts. I put it back together and started it up. The motor still had a hard time priming, but got a nice stream coming from the pee-hole.
Still, motor overheated after 2 minutes.
I took readings with an infrared thermometer, both heads are getting to about 185 degrees before the buzzer starts sounding, so I don?t think it?s a bad thermo-switch.
I have no idea what to do now. I don?t think there are any blockages to the water jacket due to it working fine earlier in the year. It just seems to be a low-pressure situation.
Last thing I am grasping at is when I took the original impeller out, there were none of the washers (10, 11, 12 & 13) on this graphic (Search for 1997 C150TLRV Lower Casing 1 on boats.net) - similar to my repair manual - so when I put the new stuff it doesn?t have any of those. I am curious if that could cause the low pressure situation?
Ps. Pictures are from pre-new yamaha pump installation. Pictures are of the original impeller and after installing the new gasket.
I need some help diagnosing a problem with my Yamaha. I got it out of storage after about 2 months not using it, started it to warm it up as usual on muffs at home. No problem.
Once I put it in at the lake I started it, as it idled for about 5 minutes, got the overheating buzzer. Trying to diagnose the overheating problem I have done the following:
1. Bought a Sierra impeller and installed it into the exiting housing. Didn?t help.
2. Took out and cleaned both thermostats, they were pretty gross
3. Cleaned and re-tensioned overpressure valve. This seemed to help, and the boat could idle for 5+ minutes.
In deciding that this was the problem, I ordered new thermostats, new gaskets and new overpressure valve and spring.
The next weekend I:
1. Replaced the thermostats with new, and put on new gaskets
2. Replaced the overpressure valve and painfully (because it was OLD and stuck) it?s gasket
1. Took off the lower unit again, replaced the gasket under the water pump as well as it?s gasket.
I started the engine with muffs and it proceeded to overheat in under 2 minutes!! Being convinced I screwed something up I took it all back apart, checked everything, put it back together, same result. The pump did have a tough time priming initially, so being convinced that maybe the Sierra impeller I got was bad.
I went and got a replacement pump kit from a local boat dealer and replaced the housing, casing, both seals, gasket, plate, bolts, impeller and shim - all with genuine Yamaha parts. I put it back together and started it up. The motor still had a hard time priming, but got a nice stream coming from the pee-hole.
Still, motor overheated after 2 minutes.
I took readings with an infrared thermometer, both heads are getting to about 185 degrees before the buzzer starts sounding, so I don?t think it?s a bad thermo-switch.
I have no idea what to do now. I don?t think there are any blockages to the water jacket due to it working fine earlier in the year. It just seems to be a low-pressure situation.
Last thing I am grasping at is when I took the original impeller out, there were none of the washers (10, 11, 12 & 13) on this graphic (Search for 1997 C150TLRV Lower Casing 1 on boats.net) - similar to my repair manual - so when I put the new stuff it doesn?t have any of those. I am curious if that could cause the low pressure situation?
Ps. Pictures are from pre-new yamaha pump installation. Pictures are of the original impeller and after installing the new gasket.
Attachments
Last edited:
