Steamin Rice

I have a 2002 boat with the ITS Bravo I XR drive on it. I have a mechanical trim indicator that has readings that go up to 8 on the indicator. How can I determine the max amount of trim that I can give the drive without damaging the drive? I'm guessing that there is no standard for readings on the trim indicator, so how do I determine the max trim level for my setup?

I believe that I need to look at the drive angle with the boat and see what that correlates to on my trim indicator. What is the max trim angle that is considered to be "safe" for a Bravo?

FloridianSon

For Bravo one and two( don't know about the XR) make sure that the trim-in limit pin is in the forward position(towards transom).This is the little spacer that is put in when they installed the rear bolt that holds on the two trim rams.When just useing the trim switch (not the up and out)at full trim the measurement should be 21-3/4" from the center of the bolt (at the transom) to the center of the bolt at the outher end of the trim cylinder.

Steamin Rice

Thanks for the info. On my setup I don't have a separate switch for trim, just one switch that moves the drive all the way up or all the way down. I think this is std with the HP transom assembly, right?

I'll take a look at it tonight and see if I can get a measurement like you described.

Mbam

More importantly is how high do you want to trim it? The maximum trim available is seldom the best performance unless the set up is way out of whack.

patrick22309

While we are on the subject, my trim guage/trim limit is not functioning, wires are rotted and will be replaced this winter. I currenly trim up until I fell the drive start to vibrate and then trim down just a bump until things smooth. Is this procedure OK to use for my Alpha?

Steamin Rice

Mbam, I hear what you're saying. On other boats that I have driven, the hull would let me know when I had too much trim and I would back off from there. I have put about 35 hours on this boat and am still finding out the best way to drive it. So far it seems to like a lot of trim and I haven't found a point where there seems to be too much trim. I want to continue giving more trim to see what happens, but want to be sure that I don't exceed the max available and damage my drive.

So far the highest that I've taken it is to around "6" on the mechanical indicator. The boat feels lighter and continues to pick up speed with more trim, so I wonder if I have found the amount of trim for the optimum performance in my boat.

blue thunder

I always consider optimal trim to be the max speed I can obtain, at a given rpm, without porpoising. If you trim until your boat starts to vibrate you either have a bad u-joint... or soon will if you keep doing it!!

BT

Mbam

The limit is actually supposed to be before the 2 thrust areas on the front of the drive are no longer supported by the gimbal ring. That is way too high for my taste. Most indicator cables have 3" of travel, so #8 would reperesent that much trim at the cylinder. Take a look and see where the drive sits when on #8. If you actually need this much trim for max speed there are a number of things you could optimize. If you post your max speed, RPM, drive ratio, prop pitch and style I will see if I can offer any hints. Also what kind of boat?

blackhawk

Maximum trim would be where maximum performance is.

mcollinstn

with your boat out of the water, have somebody trim the drive until the gimbal guides no longer are supporting the guides on the drive. Then back it back down until the guides overlap an inch. Take note of the drive indicator reading here and make a note that this is the absolute maximum trim position to ever be used while running. Any higher, and the drive will not be supported properly and the U-joints will be beyond the angle they are designed to transmit power.

Chances are, you have not yet trimmed to this position, but if you have and want more, then you need a prop with more bow lift OR you need to relocate some weight in the nose more rearward.