Engine alignment questions, twin 4.3l

[cloud_master]

I replaced gimball bearings last season. Checked and adjusted alignment last year. Thought I had it pretty good at the that time. This year, I pulled the drive for annual maintenance, checked alignment, and found it off pretty noticeably. It's taking the grease off the top splines pretty good, and takes effort to bottom out the alignment bar. Before I go and start moving the engine again, i decided to do a bit of internet searching.

I found there is a procedure that you take the alignment bar, engage it into the coupler, and tap the end with a mallet in the four directions to "set the gimball". I did not do that upon installation. What is the point of this? I know the gimball bearing can move in the outter ring, but it was straight when installed. Isn't moving the angle of that bearing in the ring just masking the problem of alignment being off? I'm curious if this has something to do with why my alignment is off after running it for 30 hrs. I was getting a noticeable vibration from the port engine last year, and i'm guessing this has something to do with it.

 

[alldodge]

Smacking the alignment bar once in makes sure the bearing is centered on the alignment bar. I use my hand and not a mallet. Do this several times on all kinds of directions.

Then remove, insert and remove to see if it can be done with 2 fingers in/out

 

[cloud_master]

Smacking the alignment bar once in makes sure the bearing is centered on the alignment bar. I use my hand and not a mallet. Do this several times on all kinds of directions.

Then remove, insert and remove to see if it can be done with 2 fingers in/out

Wouldn't this mask the alignment issue then? Or does the alignment procedure still likely needed after this? Just trying to understand what could have changed since last year. Thanks.

 

[AShipShow]

Moving the gimbal bearing isn't changing your alignment, it's allowing the bearing to pivot in its case to align axially with the coupler... if the two aren't axially aligned, you'll never get your alignment bar in...

If things have changed since last year, it might be time to investigate your transom for rot.

 

[achris]

Wouldn't this mask the alignment issue then? Or does the alignment procedure still likely needed after this? Just trying to understand what could have changed since last year. Thanks.

That's the procedure for installing a new bearing. If you got the alignment right when you put the bearing in, then you shouldn't need to do it again.

If you have a strong grease pattern on the top of the bar, the front of the engine is high. Moving that way is unlikely under normal circumstances. Without knowing the year of the engines, it's difficult to say what might be the problem. Being a V engine with side mounts, the collapse of the rear mounts is less likely, but not unheard of.

The other possibility that shouldn't be ignored is a rotting transom..

I would adjust the engines in an attempt to get the alignment right and then check it again in a few months...

Chris.......

 

[cloud_master]

That's the procedure for installing a new bearing. If you got the alignment right when you put the bearing in, then you shouldn't need to do it again.

If you have a strong grease pattern on the top of the bar, the front of the engine is high. Moving that way is unlikely under normal circumstances. Without knowing the year of the engines, it's difficult to say what might be the problem. Being a V engine with side mounts, the collapse of the rear mounts is less likely, but not unheard of.

The other possibility that shouldn't be ignored is a rotting transom..

I would adjust the engines in an attempt to get the alignment right and then check it again in a few months...

Chris.......

Last year when i took out the old gimball bearing, i noted previous owner did not install it correctly, and had it not fully seated against the back lip. It was cocked in the bore as well. Alignment was way off after installing new bearing, and i assumed it was due to an alignment to a gimball bearing that was improperly installed. I believe, without jumping in the hell hole and double checking, i had to raise that engine last year to make alignment correct. So i'm not sure. Perhaps me not "setting the gimball bearing" had something to do with it, and something shifted. Or perhaps, i just went too high with the motor and made poor judgment on the alignment being good. Either way, since i just did alignment on my other boat and recently felt how i got that bar to go in and out, this port engine is out considerably.

I'll set the bearing, and then recheck. I'll likely just need to bring the engine back down. I'm curious what my stbd engine is; i'll be pulling that drive tomorrow.

 

[tank1949]

last year when i took out the old gimball bearing, i noted previous owner did not install it correctly, and had it not fully seated against the back lip. It was cocked in the bore as well. Alignment was way off after installing new bearing, and i assumed it was due to an alignment to a gimball bearing that was improperly installed. I believe, without jumping in the hell hole and double checking, i had to raise that engine last year to make alignment correct. So i'm not sure. Perhaps me not "setting the gimball bearing" had something to do with it, and something shifted. Or perhaps, i just went too high with the motor and made poor judgment on the alignment being good. Either way, since i just did alignment on my other boat and recently felt how i got that bar to go in and out, this port engine is out considerably.

I'll set the bearing, and then recheck. I'll likely just need to bring the engine back down. I'm curious what my stbd engine is; i'll be pulling that drive tomorrow.

check for transom rot too!

 

[Rick Stephens]

A few thoughts. A gimbal bearing is needed because the support for the drive shaft that bearing provides is not directly fixed to the engine and its coupler. If Merc had made a more substantial attachment they could have left out the gimbaling part of that bearing. If you install a gimbal bearing and shine a light through it at the coupler you can see how aiming it is important. Once aimed, it has no further effect on alignment. Gimbal bearings are very stiff and do not gimbal in use. So once set straight that particular function is no longer used.

Being they are a really tight fit, I personally used a 2 pound deadblow hammer to knock my alignment bar up down left and right while it was inserted into the coupler instead of my hand. I had first looked through the gimbal bearing with a flashlight and eyeballed it, and used the alignment bar to rough it into aim using it as a pry bar. Last time I actually changed alignment was when I changed to a different motor. It started off with it way out, naturally since I had just built the motor mounts. My alignment bar would just barely start into the coupler because the engine was too low in front. Too low in front angles the coupler splines downward onto the top front tip of the alignment bar.

A soft transom will allow the gimbal housing to sag. This moves the gimbal bearing and the driveshaft down, and also will show on the alignment bar as a too tall motor. One of the things you can do to check that is to stand on your outdrive and bounce up and down, hard, on it. The drive is designed to take a many times more pressure than that, so you can't hurt it. However a good transom will allow no movement of the gimbal housing at all.

The other way to check for a water softened transom is to drill some test holes in the transom wood, down low from the inside. Never seen a 2 engine bilge with much access down there though. At least not without pulling a motor. So the bounce test and figuring by virtue of how the alignment stays is going to have to be the clues you go by. Which is what Chris recommended in post #5.

Good luck!

Rick

 

[cloud_master]

Thanks for the info.

 

[cloud_master]

A little feedback on this. I aligned the port motor again, took about two turns motor down to get alignment. What i noticed is i'm pretty much back where it was last year. In counting the threads under the nut, its one thread less than stbd motor. So they are close.

 

[alldodge]

counting the threads under the nut

I would not do that, your working with fiberglass and the transom plate to motor mounts do not have the exact same distance from each other

 

[Rick Stephens]

I would not do that, your working with fiberglass and the transom plate to motor mounts do not have the exact same distance from each other

If you have the motor mounts now uneven height, the way it is taken back to even is to support the motor by the alignment loop on top and in the front of the motor. Unbolt the mounts from the stringers and set both sides to just barely touch. Then rebolt to stringer and do your alignment. Almost no mounting pads are perfectly even height. Not something any boat builder wastes a lot of measuring time on when motor mounts will need adjusting anyway.