yamaha 250 99 mod , wont rev above 1500 rpm in the water but run perfect out

[mightymax]

hi everyone , i recently purchased a 1999 model 250AETO ( yamaha ) and the engine runs perfectly with out a load , its responsive and revs up nicely
then when i put it in the water it gets to about 15oo rpm and just starts spitting and wont pick up any speed . i by passed the fuel filters and water seperators to make sure it wasnt a clogged filter or anything , and that made no difference at all .
no alarms are going off or anything like that .
thankyou all any suggestions will be greatly appreciated .

 

[cousinabe]

Re: yamaha 250 99 mod , wont rev above 1500 rpm in the water but run perfect out

replace fuel pumps.

 

[rodbolt]

Re: yamaha 250 99 mod , wont rev above 1500 rpm in the water but run perfect out

while fuel pumps may be an issue, the 3.1L motors were hard on them.
I would really like a picture of the engine.
AETO indicates its a NON US market motor and I need to see not only is it carbed or EFI but what sensors are on it.
couple that with how long did it sit between the last time it ran ok and when it did not.

 

[noelm]

Re: yamaha 250 99 mod , wont rev above 1500 rpm in the water but run perfect out

I assume by no load, you mean it will rev it's head off while in the driveway on the flushers? if so, that is pretty well a useless test.

 

[roger777]

Re: yamaha 250 99 mod , wont rev above 1500 rpm in the water but run perfect out

do you get the low rpms while in neutral in the water or only in gear?