We have completed sea trials number two of engine conversion. We ended up opening the gate valve completely to divert 2 inch hose worth of water past the exhaust. These pumps do put out a lot of water. As the HP per L of capacity is high they need high volumes of water for the heat exchangers.
I may remove the valve but is it nor required.
Back pressure is within the factory specifications. Towards the high side at full noise but I don't expect to run for any length of time at this speed. But still within specifications.
Temps on the exhaust are all acceptable. Max temp at max RPM was 41C on the gas side of the pong box.
Also tested temps after return to idle (as the pump backs off) and no raise of this temp with it falling back to 29c in about 10 seconds.
All other locations are lower then this.
Good news no modifications required to existing exhaust.
1. Max RPM not attained only 2130 out of possible 2400... So prop is coming off for visit to prop shop...
2. Initial kick into gear causes RPM to drop off from 600 to 550 before it come back about 4 seconds. This causes vibration. Never had this issue on old motor which was 18L V8. My engine technican says the newer 13L inline 6 has less inertia this is why it is visible.
When the prop is re-pitched we will retest to see if reduced pitch helps....
I think ultimate solution will be either Idle RPM increase of some smart software to bump up the RPM as the actuator selects gears...
Attached photos of bypass at max RPM and 3 inch raw water intake on engine.
Attached video but now sure if it will work.