need help with my engine?

[chug1106]

hi folks

bought an old fletcher on sunday and its got a yamaha 90hp 2 stroke either aet or ae its an 1987,with power trim and tilt,its also got a 2 year old yamaha control box fitted

anyway i serviced it yesterday,and put new impellor in it
took it out tonight sat letting it warm up,and there was not much water coming out the tell tale,so thought will see if it gets stronger when going,it didnt and a buzzing noise came from the control box,so let cool down and started the engine again,and it was coming out tell tale strong,so all good,so went flat out after about 1min the buzzung came back and engine started shaking like hell,looked at the tell tale and still flying out,

anyone any ideas???

thanks

gav

[robert graham]

Maybe check thermostat for proper operation.

[chug1106]

Maybe check thermostat for proper operation.

i took out the thermostat and in the housing it was all salted up,so cleaned it all and put fizzy juice down the hole to break up the salt,i also put the stat into hot water and it opened,but never got the temp it opened at,so i have ordered a new one anyway,but put the old one back in to try and see if it was just salt,but same thing happened.

if the new theromstat does not solve it,what else could it be?/

[chug1106]

new thermostat fitted,but still the same

what else could cause this???