strange noise
 

Just trying to figure out a strange noise I can only hear when I am rinsing on the hose wirring noise almost like the gears in the out drive not meshing properly hard to describe.
Took the boat to a certified merc dealer its a 1998 7.4 bravo1 tryed u joints and upper bearings same noise so we swapped it out with a known quiet bravo and guess what same noise.
You can not hear it when you lift the engine hatch only when you stand behind the boat running on the hose. noise starts around 1000 rpm and gets louder with rpm.
Any ideas? Thanks in advance this is diving me crazy!

A bad Gimble Bearing makes that noise.

put in a new one then thought maybe it was bad from the factory so put a second one in still same noise.

Does it make the noise with the drive removed? easiest way to know if it is the drive.

With that old of a boat it could be U joints not aligned properly. If the rear engine mounts sag as they get old it will cause the U joints be not align. Yes I know that the alignment tool says it is perfect but it isn't. level the bottom of the boat and then insert the alignment tool and see if it is level with the bottom of the boat. They must be parallel. I had to raise the back mounts with shims and then raise the front mounts to get mine right.

Often you can get some noise from the engine coupler and the yoke during idle especially if you have not greased it in a while.
There are two grease fitting at the rear of the motor sticking out of the engine coupler, if that is in need of grease it will give you some noise.
When you solve the issue post what the problem was.
Big Boys Toys

thanks great suggestion you would like to think the merc dealer would have tried this but i will hit it with some grease my self the funny thing is even sitting in the engine compartment with a mechanics stethoscope on the bell housing you still can not hear the noise

not sure what you mean by rear mounts rear is attached to the bravo transom assembly only the front is adjustable can what you are describing happen with this set up?

The rear mounts are built into the engine bell housing at the back of the engine. They are rubberized and can sag over time. I had to put shims under mine to get it aligned. If an engine is properly aligned the alignment shaft will be parallel with the bottom of the boat. The gimbal bearing can pivot up and down and you can get the tool to go in even though the rear mounts have sagged. If the rear mounts sag then you won't get the alignment tool to go in so you lower the front of the engine to get the tool to line up. In the process you tipped the gimbal bearing down to get it to line up with the engine. The problem is that the front of the engine output yoke is tipped up at the front U joint and does not line up with the drive input shaft when the drive is in the neutral trim position. This causes side loading of the U joints and that side loading transfers to the engine coupling making it burn out.

thanks I will have it checked going back in this week also I just greased the coupler and guess what same noise this is getting crazy