A ? about my prop!!

[Tony B]

I have a 93 21 foot Eliminator Datonia. I have a 93 2.5 EFI 260 Merc on it. The motor is stock. The best RPM and speed I can get out of it on a GPS is 75MPH at 6400RPMS. I'm running a 26 pitch chopper. Do I need a smaller or larger prop to achieve higher RPMS and speed? And is'nt my redline around 7,000RPM's

[HavasuDreamin']

Your motor should spin that prop 7,500 rpms or better which is where the motor is designed to run. My guess is something is wrong with your motor or setup. Your rig should see 85mph is my guess.
Are you sure the prop is a 26"?
[ June 25, 2003, 02:35 PM: Message edited by: HavasuDreamin' ]

[Tony B]

Positive its a 26!! I have a jack plate on the boat too. It may be I'm not trimming the boat out right. But, I have tried many different trim levels and jack heights. Nothing seems to give me the RPM's the motor is designed to run. Maybe my prop is to large?? At 5,000 RPMs my boat is running around 57MPH per GPS.

[Jrocket]

Not enough trim.
Prop is not a 26.
Prop height is too low.
Tach is wrong.
Thats what I would check..

[daytona 23]

better check the compression you may need rings. a 260 with a 26 pitch should net mid 80's on your 21 ,my 23 daytona runs 98 mph with twin 260 mercs with 26 chopper props,thats with 2 men and full tanks i did try 28" cleavers the boat handled better and was a little faster.the reason i said to check your moror is i just got done changing my rings cause the boat only ran 90 mph the rings were wore out

[HavasuDreamin']

5,000 RPM at 57 mph is about 13.5% slip which I guess isn't out of line for a tunnel running mid range.
Your jack plate should be run as high as it can go while still maintaining 12-15 lbs. of water pressure at speed. In most cases the bullet of the nose cone is even with the bottom of the center pad.........give or take a little. The trim should be about neutral at speed and the boat should be free and aired out. Under these conditions, your motor should be spinning the 26" prop in the mid 7's and you should be hitting mid to upper 80's. If this info. doesn't help, have someone check the motor out.
HD :cool:

[Tony B]

Yea, something is'nt right... I will check into the motor not turning the right RPM's. It planes very quickly with the 26 chopper. I now for a fact it is a 26 to. I will try to borrow a smaller prop over the weekend to see if I can pull 7,000 plus RPMs. If I cant it must be something with the motor.

[Tony B]

I found my problem!!!! The hot foot cable came loose. I was'nt getting full throttle!!! I turned
7100RPM's finally on a 95 degree day with 80% humidty!!! With the 26 Chopper I ran 83 MPH by GPS!!!