We have a 2000 226 with 7.4 mpi and Bravo 3. Today the trim gauge went nuts. it was bouncing all over the place - the outdrive wasn't bouncing around and the boat was flawless. I checked the screws that hold the sending units and they were tight. Also, I could be way wrong - when we shut the engine down the gauge read full "up" - it seems to me that when I shut everything off the gauge would read full "down". I check the connections on the drive pump and the gauge - all seem to be ok. We have Faria gauges Anyone have any ideas thanks in advance 3pointstar
Based on this page, it seems that the sender operates by varying it's resistance. If you have a multimeter, you might be able to isolate the sender from the gauge and determine where the issue is by testing resistance across the terminals (I believe the B+ and Signal terminals). If the multimeter and gauge jump around together, that would indicate a problem on the sender side. If the multimeter is consistent with drive position and the gauge is jumping around, it would indicate a problem on the gauge side. https://fariabeede.com/2-pages/prod_display.php?calledGauge=2_trim https://fariabeede.com/site_manuals/IS0016h.pdf
Your boat is 17 years old. If the gauge sending unit has never been replaced they are waaaaayy overdue and have been on borrowed time. It sounds like the gauge sender has water in it. It happens to all Merc drives. The kit with the senders is only about $75 but the outdrive needs to come off to do make this repair correctly. Here is a YouTube video of the process. There are also several videos showing how to make this repair without removing the drive but these are shortcuts and these fixes rarely last too long and they are not recommended by Mercruiser. I don't know when your outdrive was last pulled for service but if it were me I'd just live with it until the end of the season and if its been a few years since the bellows were changed or the gimbal bearing checked, that would be the best time to do this. I've done this repair myself several times and if not done properly you can have a leak where the cables pass through the Gimbal Housing. But as I said, if the drive has not been off and serviced for a few years it's a great time to change all bellows, replace the gimbal bearing, change those sending units and have the alignment done. I don't know what the shop manuals give for time to do this but I've done it in a day just taking my time. And you can buy a complete kit with bellows, senders, water hose, gaskets, etc. This is also a good time to change the lower shift cable as well. You will need a hinge pin tool and an alignment tool. If you decide to try this yourself I can loan you the hinge pin tool but you would need to rent the alignment tool. Shawn
My trim gauge reads "up" when the ignition is off. I have a Volvo though. Don't know if there is a difference.
One thing that happens with some older Volvos is that the hinge pin can back out crushing the sending unit. So the pin has to be screwed back in with some thread lock, and replace the sending unit. On mine, the threads were stripped, so a heli coil was placed in first, and then the pin. it took a few trys to adjust the sender so that it corresponded to the gauge, but worked great ever since. And I agree with @Mugsy- inspect and replace all the "consumable" parts while you are working back there.
