1992 2520 sport cabin twin yamaha 150s economy and speed

[panga]

Yeah I can take pics of the bottom, motors position, and props when I get the boat back on trailer in a couple days, Thanks very much for the help. The motors are 4 strokes.

 

[TopShot25]

I have a 2520SC with a notch transom and twin F-150’s. I don’t have bottom paint. My numbers are very different and I would think they should be at least close to what you should get.

Everything is depending on sea conditions of course.
4000 RPM’s about 20 knots
4300 RPM’s about 24 knots
5500 RPM’s about 36 knots
My boat is pretty heavy with all the stuff I carry so 5500 is my WOT until I get my new props.

 

[coolbreeze]

You for sure still have a problem . I have twin 115s and will out run you with my 2520 dv .. keep checking and get the rpms up. 5000 wot can cause numbers of problems. making oil is the worst .been there done that , simple prop change corrected this for me. This is like driving up hill in a car 10mph in 4th gear

 

[DaleH]

FWIW one of my other brothers in ME runs a 4-blade prop of questionable repute on his 21' cuddy (non-Parker) with a heavy Honda 130hp 4-stroke OB on the stern. His RPMs were ~5200.

I advised he get his wheel tweaked or drop at least 2" of prop and raise the OB. He got a new replacement prop of 2" less pitch, raised up the OB via my Roman leverage method (do a search) and he's up to 5900 RPMs . OEM max is 6K ... now he says his hole shot is great and the motor 'sounds' better!

Over-pitched [prop] is #1 THE worst thing for a motor ... less no oil ...

 

[JamesTX]

I agree totally. Also one of the biggest reasons for poor performance claims by their owners.

In certain applications (heavy boat moderate HP) I would rather be under propped and have to back off full throttle slightly to prevent light load over rev. Usually makes it just right for normal days.

 

[panga]

Thanks for the tips, I plan to get the bottom redone here in about a month when fishing season is good and done, then see where that lands m,e with a slick bottom. I don't think the motors are to high, because when I run in the ocean, if I trim the engines up at all to maximize performane, just a hint up, and I hit any chop the props come out of the water when hitting a bump and ventilate, causing the RPMs to jump up to 55+rpm. This leads me to believe that any higher and I would have issues with them trimmed all the way down. If the new bottom does not get me where I need to be, I will ship off the props to be reworked at the nearest prop shop.

 

[TheOtherLine]

Panga, been following this thread but I am still not clear.

Do you have 2 strokes or 4 strokes?