Re: Upgrading Power on 5.7 300hp
Naf,
please understand, it doesnt matter the specifics of which throttle body. you messed up your motor by running a ported throttle body. your boat cant use it, and all you have done is ruined the low and midrange torque, which is what you need. your motor probably ran fine, then you changed props to get a higher top end (while sacrificing the low end). then you wanted more speed and installed a ported TB and the motor fell on its face on the bottom end.
you came here looking for answers. we gave you answers, however you still have not corrected the issue and continue to ignore the advise we have given while giving flippant comments about
I may just yank the engine out and install a 6.2 GM marine LSA engine. I know the engine, i can tune it properly, and its not old tech with a new coat of pain on it...
if you install the 6.2 and mess with that, it sounds like you will mess that up too.
these are boat motors and not car motors. Any tuning you think you know on car motors does not apply here. Boat motors are loaded all the time, built for torque not speed (small TB, small valves, etc.) and are at the edge of detonation all the time. Remember, a team of engineers from both Mercury and Volvo both have spend thousands of hours getting the motors to a state of tune.
spending $2000 is nothing. everything in boating is Break Out Another Thousand. your talking installing a marinized LSA motor and that is about $14000 complete with mandatory heat exchangers, etc. plus labor and complaning on spending $2k
If you want to gain power back to low end with your setup, then do the following all at the same time:
put in 89 octane fuel
instal the original TB
instal the orignal F5 props
if you want more power across the board for about $2k, stroke your SBC to a 383 (6.2liter), use the correct pistons to increase quench, reprogram your ECM then install your F6 props back on the boat.
