Shutting down at high rpm

[mckagen]

pair of 1989 Yam 150s. run great up to about 4000 rpm. at 4200 for just 30 seconds, they both begin to shake, oil alarms go off and engines shut down if not brought to idle immediately. rebuilt powerheads about 200 hours ago. any ideas?

[Ken]

mckagen,
Sure sounds like rpm reduction mode due to overheating - but very unusual both have same symptom appear at same time.
If it has been at least three years since last water pump repair, it's time to do it. Also, you might want to pull the thermostats and pressure control valves and check all for debris that may be causing them to stick.
Good luck [img]smile.gif[/img] ,
Ken K

[Hamfisted]

Yeah dual engine setups will put both motors in SAFE mode if either has a problem and alarm. Is it a steady alarm? Or is it a beeping alarm? Which warning light is flashing on which tach when the alarm is going off? If it's the temp light then I would suggest new waterpumps in both to be sure. Then of course you can inspect the thermostats too. If it's a beeping alarm then inspect the oil tanks under the hood of whichever one is flashing.

The shaking is just the SAFE mode killing a few cylinders to bring the rpms down.


Mike