Flushing outboard motor

[mr2stroke]

Good day all.

Im new to this forum so this will be my first post I have recently just purchased a RIB 90hp 2 stroke Yamaha on the back. BEAUTIFUL !
I would just like to ask anyone with experience in flushing these engines out.
with just the normal muffs on the bottom with garden hose attached and constant cold water running through while idling? will this open the thermostat? or will I have to put the bottom into a drum and let the water heat up? I would love to know that I am able to completely flush the motor through all possible water passages.

Hope to hear from you !
cheers

[boscoe99]

Welcome. You are a long way from where I am.

With the motor being run on flush muffs the engine should come up to the temperature where the thermostat will open. The thermostat opening should do a more effective job of flushing the block IMO.

Some Yamaha's have a tendency to over temp if run on just flush muffs alone. If yours is one of those that does, and if it also has a garden hose flush fitting, you can provide the motor with water via both the lower unit inlets and also via the garden hose fitting. This will give it enough water and prevent it from over heating.

[mr2stroke]

Thanks for the reply boscoe99

I haven't experienced it overheating while flushing. I was just curious to know if with flush muffs and idling it gets hot enough to open the thermostat.

Thanks again !

[boscoe99]

Do you have an infrared temperature gun? Shoot the thermostat cover and see what temperature it indicates after the motor has been running for five minutes or so.

The thermostat will start to open at 118 ~ 126 and be fully open at 140 degrees F. If this is a 2005 and later Yamaha 90.

[TownsendsFJR1300]

+1 ^^^ on the muffs.

Just NEVER start the engine without water. It'll tear up a water pump real quick!!

[robert graham]

Mine is a 1999 C90 similar to yours and I always just put it on the muffs and run the motor for 5 or 10 minutes...never had an overheat situation....wouldn't hurt a thing to remove that little square cover that's over your thermostat and pressure control valve and inspect/clean/replace if needed...make you feel better about those items...same with water pump...