I/O engine alignment, read the grease

Dave M.

New Member
TECHNICAL Contributor
Oct 9, 2006
874
Hermiston, OR
Boat Info
270 DA
Engines
7.4L, Bravo II
I will make a post about this. I did a quick search on the internet for engine alignment, and saw a comment that mentioned reading the grease. Since I had no better idea of how to judge which way to adjust me engine alignment problem, I decided to give it a try.

So, I took my new Merc alignment tool, put a piece of duct tape on the top half in the middle to mark the top, and stuck it in through the gimbal bearing into the coupler. Then I pulled it out and looked at the marking from the coupler splines. There were on the front half of the end of the tool mostly. Here is the top photo.

aligntooltop.jpg


And here is what the tool looked like on the bottom. You can see that the spines hit the bottom a lot more towards the middle of the tool, not at the very end.

aligntoolbottom.jpg


.This seemed pretty consistent with multiple checks, and with different engine crankshaft rotations. So I conclude that the tool, as it goes into the coupler, hits the spines at the top front of the tool, and as the tool is pushed down, the coupler splines drag on the tool away from the end of it. So it seems to me that the engine front end is too low. I have not yet adjusted it at all.
 
Is it possible that it is just a function of the weight of the tool?
When I had mine checked by a mech, his interest was that the tool was centered in the housing after engaging the splines.
Are you feeling any vibration?
 
No, I can try and move the tool around, it is tight when inserted.

I do think I have a small amount of vibration, it is not much. I think I can also hear it a little bit when I trim the drive up or down from where the shaft is straight. I may be imagining things. I am sure though that I am going to replace the gimbal bearing, it definitely is not as smooth as I would like it.
 
Reading the grease marks is a pretty effective way to judge engine alignment. Also, the tool should slide in and out of the splines very easily. It is most common for an out of alignment motor to be too low in front.
 
Dave - off topic - could you tell me the dimension on the diameter of the tool that enters the splines. I have two tools with slightly different dimensions so I want to verify. If I recall one of them is 0.995" dia.

Thanks - Mark
 
Sea Ray 300 said:
When I had mine checked by a mech, his interest was that the tool was centered in the housing after engaging the splines.
I did not understand what this meant. So I went out and started adjusting. I numbered the flats on the bottom nut, starting with "0" as the starting position. I went one flat at a time, 1/6th turn, each side, to see how it went. When I started, I could not fully insert the tool except in one crankshaft position. After 4 flats, one at a time, I could tell I was making progress, but it was slow.

At one full turn, I could insert the tool in all crankshaft rotations, and could also feel meaning of "centered in the housing". When you get really close, then you can feel the splines, but they do not keep the tool from sliding back out easily. When you are sort of close, the tool goes in all the way, but the splines put a drag on it so you have to tug it a bit to pull it out.

I stopped at 1 1/3 turns. The tool slides in and out quite well, except where a tiny bit of coupler skew wants to grab it from the side at some particular crank rotation (actually it is worst at my original crank reference mark). Then it is not totally smooth coming out, but more vertical adjustment won't fix that. You can see from the grease marks that the splines are the same top and bottom, just not the same left to right.

Boatrboy, I will go out and check and see if I can measure the shaft for you. Not sure I have a tool that is accurate enough, but will look.
 
Boatrboy
I only have a cheap plastic gauge to measure the shaft. But I measured it anyway. It seems to read 1.01". There is no way I can make the gauge read 0.995" on the shaft.
 
Sea Ray 300 said:
centered in the housing after engaging the splines.

Dave,
I hope that my reference to "centered" helped out a bit.

In following your thread, there's no doubt that you have aligned far more precisely than anyone. Possibly even the factory.

I'd bet that 9 out of 10 are out of spec, ever so slightly, possibly a couple of thousandths, and feel that the "neoprene" coupling is there to absorb these minor discrepancies.

That being said, I salute your precision and diligence. :smt038
 
Steve, thanks for the kind words, and yes, it was helpful :thumbsup:

I had hoped to get it out on the water for a test yesterday afternoon, but my outdrive trim still indicator does not work, and grandkids birthday party somehow took priority over the boat work. :grin:
 
Dave M. said:
Boatrboy
I only have a cheap plastic gauge to measure the shaft. But I measured it anyway. It seems to read 1.01". There is no way I can make the gauge read 0.995" on the shaft.

Thanks for the info!
 
It seems that tool should be renamed gimbal bearing alignment tool. Checking the grease marks can be useful but a better indicator is a 1'' broomstick. Here's what I do.
Insert the tool and give it a good knock with a mallet. Up, down, left, right to make sure there's play in the gimbal bearing (i.e not seized, properly greased). Then I center it to align the gimbal bearing. Then to check engine alignment I insert the broomstick. With my fingertips I slowly move the end in a full circle. If you crouch behind it at eye level you can see if you get a rough circle or if it gets kind of oblong in any direction. Adjust mounts and recheck. I think that's as precise as you need to get.
 

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