Dunlap 27 porpoising !

[riggerman]

Awhile back i converted my 27 inch Dunlap tunnel hull which was powered by a OS .21 NITRO engine to 4s lipo power with a 2030 kv bl motor mounted on a K&B LOWER UNIT i inserted a 5/8 inch spacer on the transom for proper inset and set the prop c/l 5/16 of an inch above sponson bottom with X442 prop with 0 degree thrust angle while the boat runs down the straights i notice the bow porpoising lifting up and down i tried a 1/2 degree down thrust and it was even worse and moving the lipo back and forward to change c.o.g did not make any difference . What can i do to try to solve this issue ! With the nitro set up this tunnel hull ran like an outrigger. Regards Andris Golts.

 

[Mike Hughes]

Raise the motor. The prop is trying to ride on the surface. It wants to climb up out of the water. The front of the boat is now being bounced off the water which in turn buries the prop once more. Then the cycle repeats down the chute......Your change made this worse because you lowered the prop when you put neg angle in burying the prop even more. Raise it up. I know. It does not sound right.....but it is.
Mike

 

[Kris Flynn]

did you try leaving trim neutral, then raising and lowering prop (not changing thrust angle)?
Did you try other props?

 

[riggerman]

Thankyou Mike and Kris i will try your suggestions .

 

[RobertDoak]

Andris....did you solve your issue with the boat

 

[riggerman]

Hi Robert you would not believe this went to test the D-27 this past weekend snapped the flex cable 20 feet out. Replaced with another cable the new flex shaft slips on the square drive side i ordered 6 spare cables just have to wait till they show up. Robert i like the paint jobs on your two G30 tunnels Joe mailed my G30 today. Regards Andris.

 

[RobertDoak]

Wow...well get all the gremlins out of the way....
And enjoy the G30....any questions just ask