Hi Derek
Some interesting comments there, thanks..!
No plans for the boat to see salt / brackish water, so that shouldn't be an issue.
Pressure calculations are enlightening, the spec sheet mentions a 1.9m 'head', I thought that would be a useful pressure to be working with, that's about as far as I'd got. Agreed re largest bore pipes throughout to get best flow.
Hadn't thought about debris filter... Biggest issues I've had where I operate are with leaves, I had thought that with a flush inlet these should be avoided, I guess an inline mesh filter would make sense for smaller debris...
I hadn't heard the term 'flooded suction', I'm guessing this is what would happen when the inlet / pipework / pump are below the waterline and no 'air lock' in between, with an essentially open outlet side and centrifugal pump the tendency would be for the pump to fill.
I hadn't considered the flow not being even, but of course you're correct. My thought has been to split the cooling circuit into two after the pump, for the port / stbd motors / ESCs, then feed the outlets to the port / stbd exhausts. I guess I'll see by eye whether the flow is equal. If required I can add a restriction (clamp) to the max flow side.
I think I'll test the whole cooling circuit in an existing (old) model, that would highlight any issues before building problems into the Aquarama.
After UKMikes comments about the limited capabilities of the smaller pump (which I agree with) I was thinking of looking at a hybrid solution to reduce the demands / reliance on the pump, just a case of plumbing really. At the end of the day I'd like a realistic flow of water through the exhausts when at rest / low speed, so I'd thought I would need a pump when there's no / low flow past a water pickup.
I could build in conventional water pickups in the propwash, then take a feed from this pickup to the pump... Use the pumped water for the ESCs / electronics, then rejoin the outlet side to the main water circuit at (or just before) the exhausts. I'm thinking this would offer some advantages:
1. I can get away with a lighter / smaller pump.
2. A quick blip of propwash would help prime the pump.
3. Once primed, the pump would cool the ESCs / electronics full time and give realistic exhaust flow.
4. As propwash increases the flow would get to the motors via a dedicated circuit.
5. I think the pressure increase on the inlet side when at speed would be (almost but not quite) matched by the back pressure at the exhaust outlet, so the pump would not get into a 'race' condition.
6. The electronics get full time cooling.
Hope the above makes sense.
Thanks again for your comments.
Best regards to all.
David.