Am I getting enough raw water flow?

[benzy]

Had a weird scare the other week when raw water simply stopped flowing whilst we were sitting on the mooring about the cast off. Stopped and restarted a while later and the same thing happened within 10 mins. There were tonnes of jelly fish in the water (big ones) and our theory is that one came too close to the thru hull inlet and got suctioned up and stuck, covering the hole.

Anyway, just to be sure, I replaced the impeller and installed a new raw water strainer and new clear piping. The jellyfish theory is tenuous so I wanted to rule out other possibilities!

Having installed this new gear, I can now see clearly the water flowing into the raw water system. I’ve done some testing (running the engine at about 1800 rpm for a good half hour and all seems to be fine.

However, I notice that while the hose on the inlet side of the strainer is full (ie no air in the line) the pipe on the outlet side leading to the engine is not “full” (hopefully my attached gif works). This is when running at 1600rpm.



I’m trying to figure out if this is sufficient flow for the engine?

I don’t have a temp gauge (just an alarm) so can’t monitor whether it is running hot or not.

The pipe internal diameter is 19mm (which is the minimum spec as per engine manual). The manual also says a minimum of 18 ltrs/min of flow at 1500rpm - but the exhaust outlet is right on the waterline so not practical to measure it accurately.

Can anyone offer some guidance on how else I could tell? My gut feel says that the pipe should be “full” of water. But not sure.

Thanks

[wingless]

The raw water strainer plumbing is all under suction from the impeller.

The only path for that suction should be the through hull.

If the inlet to the strainer is full of water, but the outlet also has air, then there is an air leak in the strainer. That air leak should be identified and corrected.

Note that the clear plumbing is clever for diagnostics, but it should be replaced w/ appropriate double clamped below-waterline marine plumbing when the issues are resolved.

Don't forget to inspect / clean the through hull strainer.

[sailorboy1]

hardy takes any water to keep engine "cool"