# Yamaha F70 Reduced Top Speed and RPMs after tank replacement



## SFL_Mirage (May 25, 2019)

I recently had the gas tank replaced in my maverick. Prior to this, I had a whole new fuel assembly and the F70 mounted. Top end was near 38-39mph and 6200 rpms.

I had the tank replaced recently and think I have noticed my engine performance being reduced. Seems like my top end is around 32-33 now and maybe 5500 or 5600 rpms. I tried manually priming and that seemed to increase the speed to ~35mph.

that has me thinking my problem is either a leak in the fuel hose/loose connection to the tank, or the new tank is not venting properly?

any suggestions? I’m planning to check the fuel lines tomorrow and tighten everything up.


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## NealXB2003 (Jun 8, 2020)

Can you try running it on a small portable tank as a test to see if the previous performance returns?


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## Mako 181 (May 1, 2020)

More weight?
New tank bigger?


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## SFL_Mirage (May 25, 2019)

NealXB2003 said:


> Can you try running it on a small portable tank as a test to see if the previous performance returns?


I’ll need to go grab one but yeah that could be an option.


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## SFL_Mirage (May 25, 2019)

Mako 181 said:


> More weight?
> New tank bigger?


No, it was an even swap.


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## lemaymiami (Feb 9, 2007)

Running that rig on a known, good condition portable - by-passing all of your current fuel system entirely... is the first thing a pro will do. If that restores your performance - then comes the fun of figuring out exactly what's going on... Good luck and post up what you learn along the way..

One other thought... .is there any chance someone (without asking permission...) might have swapped out your prop? A different prop would account for the change in performance entirely...


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