1995 370 sea ray
I have twin 8.1 engines and zf hurth 630 trans. 200 hours on engines.
I was out cruising around at all different speeds thru the day and all of a sudden at 1100-1500 rpms I get a constant beep with starboard motor.
If I decrease throttle beep goes away. If I kick it up to say 2000 rpm it will not beep. All runs perfect, just a beep at that RPM range.

So I tried it in neutral at that same RPM range, no beep! Only happens in fwd or reverse. So it seems like its a trans issue but it shifts fine. I checked atf gear oil and it seemed ok. Maybe a tiny bit low but maybe right in the middle. Temp sensor is good, it wasn't overheating.

What in the world would make it do a constant beep at just that rpm range?
Any other sensors? I know very little about the trans.


I just ordered the vesselview system so maybe I can pull a fault code & keep an eye on things more. I'm just stumped on what could cause this.

Any ideas what I can check or what it could be?

my guess would be water pressure issue, but there's better 496 guys on here than me

With a inboard I would look at the water pressure sensor. (edit agree with speedy)
Would suggest putting a scanner on the motor to see what is happening

I did order the vesselview whcih will show fault codes so hopefully it tells me something. It's $300 cheaper than a scanner so I went that route.
But is the water pressure sensor inline with the drive unit or is it a sensor on the engine?

ok I see the sensor is on or near the impeller/water pump but also on the water line going to the trans. I don't understand why it wouldn't beep in neutral though. It only does it in gear. It seems like the water pressure should be the same as long as I hit the same RPMs (whether in gear or not) ?

free wheeling an engine in neutral is not like an engine under load,

Were just guessing right now because there isn't enough info.

I appreciate the guessing. It helps me eventually learn and find the problems. I guess I need to wait and run the scan and see.
So far, a sensor seems like the most likely issue since the boat runs perfect.

when was the last time the impellers were replaced

On this engine not long ago. A whole water pump was put in maybe 20 engine hours ago

but I can run at 3500 rpm and it’s all good and also no guardian mode.