Engine performance q

[Dudley67]

So we have an 01 5.7 VP, 344 hours, I did a WOT run two peeps, ¾ full tank of gas. 4,100RPM, trimmed up to just about cavitation. 51mph tops.... Have the same boat as the test boat.. thoughts as to low RPM’s and low top end speed?

BB50A421-FF5F-46FA-B206-3A41A52C1E12.jpeg

[okielaker]

So, if you can't reach full rpm, the classic answer is to get a lower-pitched prop.
Doesn't always guarantee faster top-end, but makes the most of the power you
do have. Also, what elevation are you at? Is the speed based on the boat's
speedometer, or GPS?

[akorcovelos]

Also need to validate the dash tach is working correctly.

[cmattj]

So, if you can't reach full rpm, the classic answer is to get a lower-pitched prop.
Doesn't always guarantee faster top-end, but makes the most of the power you
do have. Also, what elevation are you at? Is the speed based on the boat's
speedometer, or GPS?

Do you currently have F7 props with a 1:95 outdrive ( both will be stamped and printed.

As Olaker mentioned if your over propped it will strain and not free up to get those rpms.

But how are you measuring? GPS? Is the tack acurate?

It’s seems your lake starts at 500 ft so even with a barometer of 30.0 high humidity and temp can give you a Density Altitude of 3000 feet .
This also plays a role on power.

Check your gear for numbers and keep us posted.

Here’s a Cobalt snap shot of engine vs drive vs prop.
Maybe she had or needs F6?
.

[Dudley67]

Ok, good pointers, will check the props tomorrow evening we pull her out..

[Dudley67]

So update to the questions back to me. 1.95 gear, spinning F6’s, had the tach repaired by Faria Beedle, set to 8 cyl.

Still WOT, 4,100 rpms... 52mph...

The readings are off just the dash gauges, might have one or two more weekends left, need to find a GPS app for the phone for speed.

RPM’s not sure why so low...

Thanks for the support and questions back to pinpoint...

Cheers

[TommyTahoe]

I have the 5.7 GXI and run F4’s with same the gearing at 6,200 feet, 50 mph @5000rpm. You shouldn’t have a problem getting to WOT with your set up at or near sea level? Which 5.7 do you have based on the configurations above?