Bravo3 - Adjust Trim range...

[rbryn]

Is there anyway to adjust the drive trim's range of trim? We think that it's way out of line, we only get about 10 degrees of motion upward until it stops automically. Going down it goes and goes and goes but never stops autotatically - we usually stop as soon as we hear the tone in the trim change.

We noticed on a neigboring boat of the same make/model/year that they are able to trim thier drive all the way upwards until the prop just touches the water, on ours we can't get it closer than about a 1.5ft below the water line.

 

[Dick270da]

The rocker switch on the throttle/shifter is a 3 position switch. Down is down, up with light pressure is for trimming while running to prevent damage. It only allows partial movement up. Press the up position hard to raise the outdrive up fully for trailering. Once you arrive at your destination the outdrive should be lowered to let out water and ease the pressure on your bellows (shift & drive).

 

[mwph]

To answer your original question. Yes. This can be adjusted. However, In my opinion, this is not something that should be done by anyone not qualified to do so.

How are you measuring "about 10 degrees"? While trimming up until the prop touches the surface your neighbor is surely using the trailering function and this should never be done while the boat is running.

I'm not sure which switch you have. Mine, and some others use a seperate switch for trailering. If you have the three position switch that was mentioned earlier, make sure you know when the drive is entering the trailering mode.

Some very serious damage can occur if the boat is used while in the trailering position. This is why, again in my opinion, only someone qualified to do so should make any adjustments to the trim range.

 

[bartlett]

Do you have Smartcraft? If so you can customize your trim settings in the program.

 

[rbryn]

sorry... let me be a bit clearer... this is for drive trim while running (or more specifically when we are in shallow water).

We measured the 10 degree travel up/down while we were in the water with the engine off (me in the water, while the admiral hit trim up/down on the drive- engine off). There just isn't much distance moved before it stops (upward).

It's almost like there is a limiter on the drive that is set to low for the upper range, and to far for the lower range (which we can never reach because it never cuts off when moving to the down position).

I don't know if the limiter is set on the outdrive, or in the switch itself. I'm thinking its in the outdrive somewhere which means we'll need to have the boat hauled (we don't have a trailer) to check it out.

 

[rbryn]

Do you have Smartcraft? If so you can customize your trim settings in the program.

Nope, that's about the 3rd item on my to-do list - swtich to smartcraft guages

Engine supports it but we don't have anything using smartcraft yet.

 

[Henry Boyd]

The trim portion you are referring to sounds right. The adjustment range is actually quite small. I've never measured it but the 10 degrees you mention sounds about right for what I have observed on my BIII.

The BIII driveshaft spins all of the time when the engine is running. Even when the drive is in neutral. That means the driveshaft u-joint is under a lot of load at the extreme angle created in the trailer range. I know the Merc manual says that it is ok to go slowly with the drive in the trailer range. And if you have to, you have to. But that being said I would minimizing the amount of run time with the drive all the way up.


Henry

 

[Presentation]

Bryns, in addition to the trim-up button there is a second button called the trailer button. Only when the engine is off should you raise the trim beyond the trim-up limit.

With the engine off, look around the throttle area. It’s there somewhere. I’ve seen a second little rubber covered button half way up the throttles, a second switch at the top, a three position switch at the top, a separate switch at the bottom.

Be sure to but the trim back down before you start the engine.

 

[Great lakes pirate]

There is a shim block on the aft portion of the hydraulic rams. If it is removed and installed it can make the drive go further up or further down based on the orientation.

 

[garryowen]

sorry... let me be a bit clearer... this is for drive trim while running (or more specifically when we are in shallow water).

We measured the 10 degree travel up/down while we were in the water with the engine off (me in the water, while the admiral hit trim up/down on the drive- engine off). There just isn't much distance moved before it stops (upward).

It's almost like there is a limiter on the drive that is set to low for the upper range, and to far for the lower range (which we can never reach because it never cuts off when moving to the down position).

I don't know if the limiter is set on the outdrive, or in the switch itself. I'm thinking its in the outdrive somewhere which means we'll need to have the boat hauled (we don't have a trailer) to check it out.

i dont think you understand the operation of your trim unit on your boat


there is no degree measurement for the hight to raise the drive.

there is a trim sensor located on the left side of the gimbal ring.
there is another on the right that operates the trim gauge in the dash.
these black puck looking round plastic pieces are held on with 2 screws, one on the top one on the bottom. both are adjustable by backing out the screws enough to rotating the puck, the holes in the puck are slotted to allow this.

the one you are concerned with at this point is the left one. to check it you need to run the drive all the way down and then raise with your trim switch as you are doing.

what you are looking for to make sure you have the proper distance is-----Trim Limit Dimension 21-3/4 in. (552 mm)------

this is measured with a tape measured and is the distance from the center mounting bolt front to center mounting bolt rear on the lift cylinders. this is measured at the point the cylinders quit moving up when you have the switch engaged. if its to long the drive is raising to high and to short, not high enough, your problem. after you measure, loosen the two screws and rotate the puck till you are able to get the proper measurement on the lift cylinders when they stop, with the trim button.
the engine should be off while you do this. can be done in the water but much easier to do out.


this will give you enough trim and prevent you from over stressing the drive shaft u-joints and trimming out of the gimbal ring support and running.

 

[garryowen]

i cut a yard stick to the proper length, making a gauge to do this in the water.

you are working by feel and its easier for me to stick the yard stick on each end of the bolts and fell whether long or short till you get the right distance


you have to get into the water and be able to move around the drive. i dont think you can reach it from a swim platform or dock

 

[Henry Boyd]

There is a shim block on the aft portion of the hydraulic rams. If it is removed and installed it can make the drive go further up or further down based on the orientation.

Bad and dangerous advice! The Bravo service manual warns that that changing this shim around can create an unstable, and or, uncontrollable condition. This is what Mercruiser Service Manual # 28 has to say:

Some boats, predominantly deep-Vee heavy boats, will roll up on their side under certain
specific operating conditions. The roll can be either to port or starboard and may be experienced
while moving straight ahead or while making a turn. The roll occurs most frequently
at or near maximum speed, with the drive unit trimmed at or near full IN. While the boat will
not roll completely over, the roll may be sufficient to unseat the operator or passengers, and
thereby create an unsafe situation.
The roll is caused by stern lift. Stern lift can be created by excessive drive unit trim In. Under
these extreme stern lift/bow down conditions, instability can be created which may cause
the boat to roll. Weight distribution to the stern can reduce stern lift and, in some circumstances,
eliminate the condition. Weight distribution in the bow, port or starboard, may worsen
the condition.
The Trim-In Limit devices reduce stern lift by preventing the drive unit from reaching the last
few degrees of full trim under. While this device should reduce the rolling tendency, they may
not eliminate the tendency entirely. The need for the Trim-In Limit Insert, and the effectiveness
of them, can only be determined through boat testing and is ultimately the responsibility
of the boat manufacturer.
WARNING
It is recommended that only qualified personnel adjust the Trim-In Limit Insert. Boat
must be water tested after adjusting the device to ensure that the modified trim IN
range does not cause the boat to exhibit an undesirable boat handling characteristic
if the drive unit is trimmed IN at higher speeds. Increased trim IN range may
cause handling problems on some boats which could result in personal injury.
IMPORTANT: On Bravo One, Two and Three Models, the Trim-In Limit Insert , must be
properly positioned before installing the trim cylinder anchor pin in the following
steps.


Henry

 

[Presentation]

pffft Henry.

This guy did not need no silly trim thingy

This boat was rebuilt in front of my boat over the past winter.

 

[Presentation]

Us amateur recreational boaters came to the conclusion that the stepped hull boat had the drives too tucked in (down) at a high speed causing the boat to be bow biased as described by the Mercury bulletin that Henry posted above.

When they made a turn by the island in the photo, locally called boom island, the boat rolled.

 

[Woody]

Is there anyway to adjust the drive trim's range of trim? We think that it's way out of line, we only get about 10 degrees of motion upward until it stops automically. Going down it goes and goes and goes but never stops autotatically - we usually stop as soon as we hear the tone in the trim change.

We noticed on a neigboring boat of the same make/model/year that they are able to trim thier drive all the way upwards until the prop just touches the water, on ours we can't get it closer than about a 1.5ft below the water line.

sorry... let me be a bit clearer... this is for drive trim while running (or more specifically when we are in shallow water).

I don't know if the limiter is set on the outdrive, or in the switch itself. I'm thinking its in the outdrive somewhere which means we'll need to have the boat hauled (we don't have a trailer) to check it out.

All three of my boats worked like that.

As already said here there isn’t much movement. According to Mercruiser normal operating range for your drive is -2 to +14 degrees. The trailering range goes from there up to 51degrees. Avoid running your engine while in the trailer range. I think this is what you see the other boats doing in the shallow water. Before paying to have your boat hauled why don’t you get the neighboring boaters opinion as to whether yours is working correctly. Invite him on board and let him try it. He's got the same boat as you and he can get his drive up, right? It’s not clear to me that you know how to put your drive in trailer range…do you know how?

 

[Great lakes pirate]

My point was that the shim may be installed backwards.

 

[Lazy Daze]

Bryn, with a light load, can you get your RPM's into the max range? I think the range is 4800 to 5200 for your engine. If you can attain that, then don't even worry about anything else since trimming higher wouldn't be needed, anyways. Added to this would be, as mentioned, possible instability issues (although, in real world use, it's unlikely that a few more degrees would cause any problems at the speeds your boat goes).

Also, measuring from bolt center to bolt center as Gary mentioned is the best way to know if your drive trim/swing is within spec. You should be able to find this info in your engine manual, by the way, if you wanted to double check.

 

[rbryn]

thanks everyone for the feedback...

what you are looking for to make sure you have the proper distance is-----Trim Limit Dimension 21-3/4 in. (552 mm)------

Thanks Garyowen...thats part of what I was looking for. I know now the i'm within specs and that the limited range is normal. I'm measuring 20 1/2in right now in range.. just thought it would be more

It’s not clear to me that you know how to put your drive in trailer range…do you know how?

Woody - you are correct...I have no idea how to get it into trailer mode. I looked all over the throttle today and didn't see anything special. With the engine off, the 3 position trim switch on the throttle itself gave up no clues either... pressed all the way in it goes no further.

The trailering range goes from there up to 51degrees. Avoid running your engine while in the trailer range. I think this is what you see the other boats doing in the shallow water. Before paying to have your boat hauled why don’t you get the neighboring boaters opinion as to whether yours is working correctly. Invite him on board and let him try it.

Thanks for the advice. I would never dream of operating it with it that high - even for short periods due to the stress on the drive. My primary reason for asking was saving SeaTow a trip out when I drift over that sandbar and get stuck. Many times if we could have just lifted the drive a little bit futher we could have drifted off. It's definltly easier to push the boat off the sandbar when the outdrive isn't stuck in it

 

[garryowen]

:grin:rbryn; sounds like your good to go. i'm with you on not moving it if it's that close now.

to put your mind at rest , the measurement i quoted came from MerCruiser #28 Bravo Sterndrives

if you find your trailer switch, that sound like you will solve your problem. with out rereading the thread i will add this. you can run your drive in trailer position BUT AT A IDLE ONLY, FOR SHORT TIMES.

once in a while we raise ours like that to beach ect. just remmber, you are putting more angle on your drive shaft and u-joints, and the drive is out of the slides on gimbal support so you don't have any side support. all pressure is on the top and bottom and 2 side pins at this point.
i think someone mentioned this. better safe. happy boating:thumbsup:

 

[Ray McDaniel]

Do you have Smartcraft? If so you can customize your trim settings in the program.