Page 1 of 2
356 AC trim tab question
Posted: May 17th, 2021, 9:38 pm
by V12diablo
So, I fired up both engines this weekend , tested the transmissions, and all seamed good. Tested the trim tabs on both sides and the did not seem to move down, the would move up slowly. Is there a procedure for testing these or is there anything I should be looking for. All this was down out of the water as the boat is still on blocks.
Jason
Re: 356 AC trim tab question
Posted: May 20th, 2021, 9:55 am
by bud37
Check the reservoir for fluid level first......
Re: 356 AC trim tab question
Posted: May 20th, 2021, 10:31 am
by Cooler
Most likely low on fluid. Make sure you bring a small ended bottle to fill. The fill tube on the res is real small. If they are Bennett's, they will self bleed when you fill and run up and down a few times. Put in full up position when you check level.

er
Re: 356 AC trim tab question
Posted: May 20th, 2021, 9:40 pm
by Viper
When you check the fluid level, check the colour of the fluid too. Should be a clear red ATF. If it's cloudy or pink, you likely have a leak that should be looked after prior to launch. Check the top and bottom of the tab actuators for an oily film/discolouration, it's a sure sign it's leaking if either of those areas look wet.
Re: 356 AC trim tab question
Posted: May 21st, 2021, 9:39 pm
by V12diablo
Where about is the reservoir? I looked under the bed in the aft cabin and under some of the hatch’s in there also but didn’t see it.
Jason
Re: 356 AC trim tab question
Posted: May 21st, 2021, 10:01 pm
by km1125
A friend of mine that had a 356 says "along the transom, underneath the aft cabin nightstand". Hope that helps.
Re: 356 AC trim tab question
Posted: May 24th, 2021, 10:22 pm
by V12diablo
So the reservoir was empty,almost completely. There looked to be a small amount of fluid in the bilge, but not much. Is it common for the fluid to leak. I cleaned everything, cycled the tabs several times and did not see any fluid leaks.
Jason
Re: 356 AC trim tab question
Posted: May 25th, 2021, 3:36 am
by mjk1040
Not common to leak fluid, you have an issue.
Re: 356 AC trim tab question
Posted: May 25th, 2021, 6:37 am
by Viper
Ya you shouldn't have any fluid in the bilge. Make sure the fittings at the pump and transom are tight and that the reservoir isn't cracked. Also, wrap your hand around each line and run it from the pump to the actuator fitting going through the transom. If you see any fluid on your hand, replace that line. As I mentioned above, you should also be checking the actuators on the tabs for leaks too.
Re: 356 AC trim tab question
Posted: May 25th, 2021, 10:13 am
by km1125
If you only found a small amount in the bilge, it is possible that more got pumped out of the bilge with bilge water? If not, then you might have two issues...a tiny one inside and a bigger one outside.
Operate them a bit at the dock and then go back by the tabs and see if there are any signs of oil in the water. If there is, you might be able to stop a leak just by grabbing the cylinder and tightening it a bit (not so much you break something!). There are a couple O-rings in those cylinders that can be replaced if that doesn't fix it. On a 356 I don't think you'd be able to do the replacements in the water but on some boats you can.