WOT RPM / Speed 268 sundancer

[Frankiea87]

hey guys i have a 1988 268 sundancer with a 454 merc and alpha drive. anyways i tuned up my boat with new wires/ rotor/cap/carb/prop..... so i was out and at WOT i was getting 4500rpm and 31mph without trimming the drive. WOT for this motor is 4200-4600rpm.... so i assume im in good range? or what? should i be higher then that and control the WOT rpm between 4200 and 4600? or does that meen the WOT tops out in the range?

 

[sbw1]

You are good to go. Prop tune might give you another 50-100 rpms.

 

[jrurhh]

I think you rpm are high and the speed is low. I had a 268 for a long time and I could get over 40 miles per hour. My rpm's did get up to 4400 until I had the drive trimed way up.

Even with the drive not trimed at all I could to 26-27 MPH at 3200 rpm's. I would try a prop with more pitch.

 

[Frankiea87]

im already at a 3 blade with 21 pitch...i need higher???

 

[EricW]

No, you don't need more pitch. Sounds like you might be getting a lot of prop slippage, or your hull bottom is dirty. What kind of 3 blade prop are you running? I think a quality 3 or 4 blade Stainless prop with at least 15" diameter is what you need -- like a Mirage Plus or Revolution 4. You might need increased blade area. If you get a prop that bites well, a 17" pitch prop should put you near 40 mph and 4200-4600 rpm.

 

[CV-23]

I think you rpm are high and the speed is low. I had a 268 for a long time and I could get over 40 miles per hour. My rpm's did get up to 4400 until I had the drive trimed way up.

Even with the drive not trimed at all I could to 26-27 MPH at 3200 rpm's. I would try a prop with more pitch.

40mph? Seems a bit high with an Alpha1. My speedo breaks 40 but gps says 37-38mph max with a 454/Bravo1 in my 270. I think his prop slip is a tad high. A 4 blade with some cup in it will work better, Mike.

 

[Frankiea87]

what do u meen by slipping?

 

[kbsunlovers]

No prop is 100% efficient, so a 17p prop will not move you 17 inches through the water with one revolution. A lot of factors, including blade design and stiffness contribute to slip, and the same prop will slip differently with different loads & hull configurations. Google prop slip calculator to get some ideas of where you're at.