SML Boomer
Cadet
- Joined
- May 4, 2008
- Messages
- 28
I have a 100 HP Evinrude on an 18' Starcraft semi-vee, 800 lb. aluminum bass boat. After reading post on this site, and getting the engine running properly, I raised the motor two holes and removed a hydrofoil. This "freed" up the rig quite a bit and increased both speed and rpm's. However, I get too much porpoising to stay at WOT. Also, while at WOT the RPM's and speed indicate excessive prop slipage. Here is the data:
Prior to raising motor: 21" SST- 5000 RPM WOT- 36-37 MPH
Raising motor & removing fin: 21" SST- 5500 RPM WOT - 41 MPH (Porpoising)
Borrowed 18" Raker prop. 18" Raker 5800-6000-( some throttle left ) 40-41 MPH ( Porpoising ). Re attach fin- no difference.
I have to trim down to about 4:30 position on trim gauge to stop porpoising.
This slows RPM's and cuts the speed down to low 30's.
I put about 140 lbs. of batteries on the bow and it minimizes propoising but
also cuts speed. Bottom of hull has no hook or rocker.
What would be the next order of trials? Prop- jack plate- tabs?
Prior to raising motor: 21" SST- 5000 RPM WOT- 36-37 MPH
Raising motor & removing fin: 21" SST- 5500 RPM WOT - 41 MPH (Porpoising)
Borrowed 18" Raker prop. 18" Raker 5800-6000-( some throttle left ) 40-41 MPH ( Porpoising ). Re attach fin- no difference.
I have to trim down to about 4:30 position on trim gauge to stop porpoising.
This slows RPM's and cuts the speed down to low 30's.
I put about 140 lbs. of batteries on the bow and it minimizes propoising but
also cuts speed. Bottom of hull has no hook or rocker.
What would be the next order of trials? Prop- jack plate- tabs?
