Overtemp problem

[Grandpa Chuck]

Have a 2001 Hewes Redfisher16 with a 90hp Yamaha 2 cycle. Engine ran fine while fishing, but got an overtemp alarm after flushing for 3min30sec.on the muffs. Had great waterflow from telltale and out of prop. Tell tale water was hot rather than just slightly warm as usual.

Put a new waterpump in, and a new thermostat, and a new grommet for the poppet valve. Still overheats after about 3 1/2 min. pulled the water jacket off the head, and all was clean (I use Saltaway every time I use the motor as I flush it).

Hooked hose to the hose fitting for a reverse flush with the water jacket off, and water flowed out of all 4 ports that connect to the waterjacket, as well as the exhaust plate telltale.

Tested the Overtemp sensor (normal operations at specified temps), and the new thermostat (also normal ops but about 5 deg high)

Considering taking off the exhaust plate to see what its like around the cylinder block waterjack volume, but since the head waterjacket is clean, don't want to pull things apart if its probably clean like the head waterjacket.

Any ideas?????

Thanks!, and a Merry Christmas to all!!

Grandpa Chuck

[ausnoelm]

Did you replace the entire water pump, or just the impellor?

[99yam40]

I have dropped the lower unit on my brothers C60 that was setting off the over heat at higher RPMs
and rigged up hose to the pipe heading to block, hooded that to water hose and pulled the stat.
ran water at full blast along with shooting compressed air into that hose also off and on to force water and air around to help work out sand/shell bits out that settled in the bottom of cooling jackets.
it stopped his overheating

[zenoahphobic]

Check that the muffs seal well and that you have good water pressure to them. It common that rushing with muffs doesn't provide enough pressure by the pump to push enough water, for the above reasons including air mixing with the water going to the pump.

[TownsendsFJR1300]

How much corrosion did you see inside the block when the thermostat was out?

Also, pulling the exterior(to the water jacket) anodes may re-veal if there's any salt build up and or how much.

Plus one on all the above posts as well. Flushing with the anodes/T-stat out may help with any debris removal.

I suspect (if you have plenty of water volume, tight fit with muffs) you may be borderline with having salt water build up in the head / water passages.


Should there be a bit of salt build up, there's several threads here (do a search) about Rydlem and Citric flushing that's been pretty successful.


Did (since finding this issue) you try running the engine at idle in water (where you boat)?

BTW, time, constant on/off (normal use) in salt water will cook salt to the block /head. Even using SA.

[pstephens46]

As the posts indicated above. Run the engine in the water and see how it does. Don't waste time and energy taking a bunch of stuff apart.