I have a 250 Yammie on a 24’ Shearwater and when wide open the RPMS will surge 2-3 hundred rpms and the boat seems to dance a little. I can’t figure out if this is prop slip or something mschanical. My transducer which is tunnel mounted ahead of the motor has lost part of the puck (lowrance p.o.s.) no longer reads bottom and may be deflecting water down and causing the slip. Any ideas would be appreciated. The surge goes from 5600 rpm to 5900 rpm @ wfo. Surge still happens at lower RPM but not as bad.
OX66?? If so the range is 4500-5500.
Four Stroke
It is very possibly that the transducer is the cause. I troubleshot a similar situation on a 29’ Albemarle not to long ago. Turned out the water pickups were shadowing the entrance of the tunnels and the engines would surge. Depending on where the tranducer is in the tunnel, turning the boat in either direction may make it better or worse. If it is an engine problem it will stay consistent regardless. Trim should also have an effect if it is aeration.
Iain Pelto
Sea Hunt Triton 160 w/ 90 ETEC “JB3”
Native Manta Ray 14
Thanks I am going to pull the transducer and see if problem goes away. I have never had a transducer seperrate before. I lost botttom and when pulled up to the beach at Capers felt underside of transducer and the sonar portion had seperated and gone away. Got a slight shock from the remaining portion of the transducer. I have another transducer (someone stole my unit when boat was new) when replaced insurance just covered the whole thing so I have a spare. Once again thanks for the input.
try that but i think you are going to find a fuel restriction
if it were teh transducer causing a new “surge”, the rpms would be above the normal 5900