Hi Bill
My problem with The VST was that,
a) The salt water chamber was clogged up with a corrosion deposit that would not allow water flow ie no cooling.
b) The base of the fuel float chamber had rotted through from the salt water chamber allowing salt water to contaminate the fuel!
I am...
You are right to be surprised.
I had something similar, I put clear hoses from both T'stat outlets to the manifolds and could see hardly any water flow at 600 RPM however at 3000 RPM I could clearly see exhaust gas in the flow.
The water pickup tube in the lower outboard leg had been burnt...
Just a quick note, when I start my motor it idles at 650rpm the dashboard gauge remains at 10 volts, but as soon as I rev beyond 1000rpm it goes up to just over 13 volts, it has been like that for 25 seasons, so I have stopped worrying about it. :)
Well, after arranging to remove outboard leg etc. I Ran the motor again and realised that the noise had increased and was from the Circulating pump at the front. Renewed pump and all is well . :-)
Below is a recording of the noise from the rear of the engine. (admin needs to allow MP4 file)
I suspect it might be the gimbal bearing, but would like a confirmation.
Engine is 5.0 Gi PWTR with DP-SM outdrive with 725 hours.
Gimbal Bearing and UJ's greased and new bellows fitted before...
The SX and DP-SM drives (you don't say what you have) the grease nipple (zerk) is screwed into the female end of a plastic tube. The other end is just slightly tapered and is just glued into the gimbal housing.
The Plastic Nipple No.9 with the boat at rest is well below the waterline, so would not cause a lack of flow until the boat was on the plane.
I blanked off the outlet from the raw water pump and pressure tested via hose No. 18 to 15 psi with no leaks.
I ran 2 x clear tubes from T'stat housing...
How old is the motor? I had a similar problem that turned out to be a hole burnt in the dogleg tube between upper and lower units of the drive. It was sucking exhaust gasses as it runs inside the exhaust tube.
