yamaha 90 rpm's

[jlg]

i purchased a used 1997 yamaha 90 and installed it on my 19 foot carolina skiff,i had no prop so i tried a 13x19 max rpm's were 2400 i then looked at website for yamaha and they recomend a 13 1/4x17 so that is what i purchased and put that prop on my max rpm now is 2900 and if i force it or try to go faster it overheats?(in other words i can only put the throttle to 3/4 of the way after that i press and no response at all from engine) the buzzer goes off and it drops to 2000 rpm's and i check the weep hole and it is not hot but i let it cool down and within a few minutes it is fine and i drive off, i have been using this boat like this for the last 3 months just not going over 2900 rpm and have had no trouble<br />i have rebuilt the carbs,replaced the fuel pump,water pump,spark plugs and i checked the electronics and the stater was reading incorrectly so i replaced it and that was not it<br />i dont want to waste any more money but i cannot afford to send to the dealer, any ideas would help<br />also compression was 115,115,120 and while running we try the primer bulb and it is hard but i replaced it also just in case and still no full rpm's thanks tojorge@yahoo.com

 

[rodbolt]

Re: yamaha 90 rpm's

hello<br /> the next step is mandatory.<br /> you must run the engine on a test wheel or dyno. that will tell if the motor is capeable of making power. the IDC dyno specs and test wheel specs are in the tune up guide. the overheat I suspect will be caused by a cooling system failure. go ahead and replace the pressure valve grommet,t-stat and water pump and be ready to replace a head gasket as well. but first you must coirrect the motor/prop problem.<br /> good luck and keep posting

 

[jlg]

Re: yamaha 90 rpm's

I ALREADY DID CHANGE THE THREMOSTAT AND RELIEF VALVE,I NOTICED IT IS WHEN THE ECM GETS TO THE MAX (INDICATOR) AND THERE IS STILL 1/4 THROTTLE STILL LEFT AND I TRY TO ACCELERATE IT WONT GO NOTHING HAPPENS,I SEE THE CARBS OPEN UP BUT NOTHING,IF I LEAVE IT LIKE THAT FOR A MINUTE THAT IS WHEN IT OVERHEATS,IF I DO NOT PASS THE MAX<br />MARK ON THE ECM IT RUNS FINE (LINKAGE) ALL DAY

 

[RUSCOO]

Re: yamaha 90 rpm's

I have the same: carolina skiff 19' and I put a 1989 90 on it.. I rebuilted the carbs, new water pump, new fuel pump, new plugs and have the same prop. I can't get over 3600 rpm thou. I plan on bringing the prop to the shop. He is good at adding pitch to props according to the boat you have.. But the only problem I have with the motor is that it runs hot --quick.. Pull the head off and found my problem.. there is alot of corrosion inside.. causing inproper water flow..the person before me must of used it in alot of salt water and never flushed it out..