Yahaha 2003 F90TLRB FLAT spot

[rodsquest]

I took my boat to the local repair shop because it was very hard to start an run. My tank was drained and gas disposed. The carburetors were cleaned and it started and ran. Motor starts and idles smoothly. Acceleration smooth up to 1400 rpm and then it starts running rough and will stall unless I only increase the throttle very slowly and then it will catch and accelerate to max and run strong. Repair shop said to run it hard to clear it. I have taken it out 3 times and it ran as described but the 3rd trip was at 7,000 ft. And it would not go beyond 1400 rpm without stalling but ran smooth from 0 to 1400 rpm.
I have a water fuel separator, inline fuel filter, New gas with Yamahalube ring free plus fuel additive. Motor has 600 hours and all maintenance current. The motor runs perfectly other than at 1400 rpm? Any thoughts or input would be great! , thanks

 

[99yam40]

did you swap props when you went to 7K ft?
Motor cannot generate the same HP when the air gets thin up there. less O2

 

[rodsquest]

At 7,000 ft. it ran the same as at 1500 ft except not being able to every so slowly increase the throttle. As long as I kept it below 1400 rpm it ran perfect. Thanks for your response.

 

[99yam40]

do you not under stand the motor cannot produce the same HP at a higher level, so need for a less pitch prop, smaller diameter prop, or both maybe

 

[rodsquest]

Yes I understand your point. I don't plan on using my boat at 7k ft. I only go to local lakes around 1,000 ft. I just had a chance to go to the eastern sierras and my problem is not a prop size. Before you respond again please read and understand the post.

 

[99yam40]

I took my boat to the local repair shop because it was very hard to start an run. My tank was drained and gas disposed. The carburetors were cleaned and it started and ran. Motor starts and idles smoothly. Acceleration smooth up to 1400 rpm and then it starts running rough and will stall unless I only increase the throttle very slowly and then it will catch and accelerate to max and run strong. Repair shop said to run it hard to clear it. I have taken it out 3 times and it ran as described but the 3rd trip was at 7,000 ft. And it would not go beyond 1400 rpm without stalling but ran smooth from 0 to 1400 rpm.
I have a water fuel separator, inline fuel filter, New gas with Yamahalube ring free plus fuel additive. Motor has 600 hours and all maintenance current. The motor runs perfectly other than at 1400 rpm? Any thoughts or input would be great! , thanks

I did read your post did you?