i was told to post here

[scon]

20ft skiboat 305 chevy in alpha one out. 21 p prop goin by instrument panel rpm at WOP is 3800-4000 tops and speed is 40-42.. just adjust throttle cable it was out of adjustment a little now im getting all i can ........seems like its easier to plain out then to gain speed after plain???? is it possibly my prop size and what reccomendation do any of you have???

 

[Oldskool]

Re: i was told to post here

You aren't turning near enough rpm's at WOT, if your tach is accurate. A 19 pitch should pick up an additional 300 to 400 rpm, though you really want to be at around 4600 to 4800 WOT. At 3800 to 4000, you are really lugging the engine and putting a lot of stress on it.

 

[Silvertip]

Re: i was told to post here

Yup -- especially since this is a ski boat.

 

[QC]

Re: i was told to post here

Did you determine if that was a 190 or 205? Need to nail down the drive ratio . . .

Oh and can you tell us more about the trim and weight in the boat at WOT?

 

[scon]

Re: i was told to post here

how do i find the ratio ? is the s/n on the outdrive going to tell us what ratio or do i need to tear it apart??? hope not.. so ill post tomorrow morning what it is since the boat is at the shop i work at.

oh and if i get time im taking my gps w/me tomorrow afternoon and ill hookup a autometer tach that i have too to make sure rpms are correct.
and i will give the most accurate WOT numbers i can

thanx again to all!

 

[QC]

Re: i was told to post here

The right way to get WOT numbers are trimmed out as fast as she will go and loaded like you will typically run her. Great plan on the tach.

Engine Model number will kind of tell us the gear ratio (5.0 or 5.0LX), S/N would be better, but then we need someone to look that up. There's always the possibility that the ratio has changed, but we'll worry about that if the numbers don't add up. If we have speed (GPS), reliable RPM, reliable pitch, then we can kinda determine if the ratio is what we think it is. A better way to say it is that if we know any three out of four numbers (speed, RPM, pitch, and gear ratio) we can zero in a little on the fourth.

 

[scon]

Re: i was told to post here

ill let u know as soon as i find out ...thanx again