90 hp overheating

[shortbuster]

hey guys, i have a 1989 90 hp yam 2 stroke. today for the first time ever it sounded the overheat alarm. it ran fine in the river , but back at the house i was flushing it and the alarm went off. water at the pisser was flowing fine but so hot it burned me. i took the cover off and the t-stat cover was too hot too touch. no water was coming out of the exhuast holes in the shaft. i cut it off and put the boat under the shed, so i haven't tried it again. i don't want to do any damage to my motor. it runs way too good to take a chance. anybody got an idea what's wrong?
thanks, eddie

[robert graham]

Drop the lower unit,inspect/replace the water pump, inspect/replace the thermostat and pressure control valve....

[lucannyamaha]

same thing happen to me last week but after i launched the boat at dock/all my parts just came and my install was easy until i over tighten the last bolt on the water pump.back to a new order.

[lucannyamaha]

ok so i made a bad mistake when i took the trim tab off the lower i did not mark it with a marker so how do you fix the steering if its off.

[shortbuster]

if the pee steam is good doesn't that mean the water pump is ok? or am i looking for something else at the pump , after i pull the lower?

thanks, eddie

[lucannyamaha]

sorry this is my first motor. am learning pretty fast thu.i ordered every thing less then 100 bucks pump gaskets bolts lock tight etc...pressure switch. thermo

[99yam40]

if the pee steam is good doesn't that mean the water pump is ok? or am i looking for something else at the pump , after i pull the lower?

thanks, eddie

If tell tail is strong as normal, pump may be OK, but when was last time it was replaced?
Check stat to see if it opens in spec or just replace with new
Check to see if PCV is sticking and not letting block fill up

May not have enough water with the ears and hose, try it in water

[mackwrench]

if your using "ear muffs" to flush it on trailer, it will have a "pee" stream even with engine off, the garden hose PSI will do that.....While I certian water pump in lower unit is prob bad, make sure water is coming out prop hub when flushing, you may have sucked in a lily pad, grass weed or the like at the boat ramp causing a restriction.....

Prob should R&R water pump kit, if any parts of pump imppeller are missing, remove exhaust manifod cover (its the larger one on the left side) and make sure there's no restriction or water pump parts in it. If the exhaust is restricted, a new pump won't fix that....also replace t-stat, all simple repairs.

As noted above put a mark on small zinc skeeg before removing it so you can put back in same place!

[robert graham]

ok so i made a bad mistake when i took the trim tab off the lower i did not mark it with a marker so how do you fix the steering if its off.

Generally on my 1999 90C Yamaha I turn that zinc fin/anode all the way to the right/starboard direction(looking at the back of the motor) and it helps a lot to overcome the torque steering from the prop...But I still have to keep my hand on the steering wheel during operation(a good idea anyway)...only way to completely overcome torque steering that I know of is with hydraulic steering.

[lucannyamaha]

i have yet experienced operating a boat so the torque steering is new to me. .the hydraulic steering in my old semi was the more the gas while corning the better it turned to get the fluid up a notch. ok well i think i will have to feel that one out. i broke the new water pump with the last bolt .that god blessing last turn cracked it so back to the order board for a new one, guess i should lay off the vitamins for a while.. the book manual dont say any thing about pounds torquing specs for that so i will give it another try when it gets here..pretty simple job other wise.

[Pacific Fisher]

I just went through an overheating episode on my 60hp 2-stroke. Ended up having to have head milled and replacing head gasket.
For sure try replacing impellor and thermostat first. Pulling a head on your 90 is easier than replacing the impeller. Take the head to a machine shop for them to check for warping.
Good luck and let us know.