5200 rpms on Chevy 350

[AdamB]

Hi, just purchased a used 21' Wellcraft Elite with a re-built Chevy 350/ Alpha one.<br /><br />My speedometer isn't working, but the rpms show 5200 at WOT trimed all the way up.<br /><br />I believe the max rpms for this motor is ~4800 right?<br /><br />I have a 14X19 prop now, was thinking of switching to 14X20, should lower rpms and possibly give higher top speed.<br /><br />What do you guys think?

 

[walleyehed]

Re: 5200 rpms on Chevy 350

Hi Adam, Welcome aboard.<br />Each manufacturer does there own little tricks to the V8's-all sizes for that matter, to marinize them. 5000 is a good target number with a normal load. The gear you will have on board and full fuel included in that "normal" load.<br />5200 no-load is OK, just don't allow it to run there all the time..pull back a little.<br />The next pitch will be 21, and I think that will hurt the over-all performance when you have a few others on board.<br />The 14X19 sounds a little small diameter-wise..are you sure thats the correct numbers???

 

[Boatist]

Re: 5200 rpms on Chevy 350

You need to go to a 21 pitch. 21 pitch will put you at 4800 rpms and give you 3 MPH plus still have a good hole shot. If you can find something 21 pitch and a little larger even better.

 

[AdamB]

Re: 5200 rpms on Chevy 350

Yeah, it is stamped 14X19. <br /><br />I had 3 people, full 45 gallons of gas, was hitting 5200 rpms, unknown speed, broken speedometer, and no gps (yet).<br /><br />I found a 14X20 prop here on iboats, but you guys think I should go with a 14X21??<br /><br />This is a rebuilt 350, with ~50 hours on it. I don't think it was built to perform better than stock, just to stock specs...the motor sounded fine, and wasn't overheating. Although it did hit 190 when I went back to idle.

 

[Doug Durako]

Re: 5200 rpms on Chevy 350

Borrow a 21 and try it---stainless steel if you can find one. You get a 200 rpm reduction per inch of pitch increase.<br /><br />You need to get back to 4800 at wide open, assuming your tach is accurate.<br /><br />Unless you want to rebuild the engine again in 50 more hours.

 

[Wart T]

Re: 5200 rpms on Chevy 350

Before you do anything like spend a bunch of money on props, verify the tach reading first. Simple and free.

 

[milkyway]

Re: 5200 rpms on Chevy 350

I have read many times not to rely on the tachometer on the dashboard to establish idle speed/rpm. Instead, one should use a tachometer that you hookup to the ignition coil and battery. I bought and used this meter last night and confident it read 650 rpm on idle. Happy with it. Now back to the tachometer on the dashboard - is the reading reliable when you are in half to full throttle? This dashboard tachometer say 4700 rpm at wot throttle, but is this truly accrurate? if i cannot rely on this to set idle speed, how reliable is it in checking rmp wot?

 

[AdamB]

Re: 5200 rpms on Chevy 350

Will verify the tach first.<br /><br />Thanks.

 

[AdamB]

Re: 5200 rpms on Chevy 350

Milkyway,<br /><br />Just leave the hand held hooked up and have a buddy read the WOT rpms if you can't (in the lake of course).

 

[milkyway]

Re: 5200 rpms on Chevy 350

Adam,<br /><br />I just realized that this tacho I bought last night has top rpm of 1500 for 8 cylinders. I think this unit which cost $29.95 is more for idle speed setting ( and dweller it says) and not anything more. I hope the store takes it back.<br /><br />Ernie