More speed from 9.9 merc

T

Tommyj11

Recruit
Joined
Jul 28, 2025
Messages
2
I HAVE A 16 FOOT BASS TRACKER 1000LBS. A NEW MERC 9.9 EFI IT RUNS ONLY ABOUT 7MPH. I'M TRYING TO GET MORE SPEED FROM IT. IT ONLY REVS TO ABOUT 3000
I HAVE CHANGED THE PROP FROM A 10X7 TO A 9.25X9
ADJUSTED THE LINKAGE TO OPEN THE THROTTLE FULLY
REMOVED THE AIR RESTRICTOR IN FRONT OF THE BUTTERFLY
RESULTS ARE
MUCH MORE RPMS, CLOSER TO 4000 INITIALLY THE BOAT SPED UP TO 13MPH BUT THE ECU TRIPS AND INITIATES WHAT I ASSUME IS A FAILSAFE, BEEPING AND ROUGH RUNNING CONDITION. I RAN IT LONGER TODAY AND IT WOULD GO INTO THAT CONDITION AFTER ONLY HITTING 8 MPH. THERE IS ALOT MORE RANGE FOR THE THROTTLE TO GO BUT THE MOTOR WONT LET IT. ANY SUGGESTIONS? serial #1A10452BK
 
Scott Danforth

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
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Jul 23, 2011
Messages
51,058
Go down in pitch

That boat is probably rated at 50-60hp. So less than 40hp will be under performing
 
Scott Danforth

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
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Jul 23, 2011
Messages
51,058
Which 16 foot bass tracker model?

The only one I found with a dry weight near 1000# has a HP rating of 50hp
 
A

airshot

Vice Admiral
Joined
Jul 22, 2008
Messages
5,698
You mentioned changing props from a 10x7 to a 9.25x9....which means you made it worse. If your only getting 3k rpm, you need less pitch on the prop. However, it sounds like you have other motor issues to address first. Get the motor running properly before swapping props.
 
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