Gimbal Ring Wear - How Bad?

[Knot 4 Me]

Have a friend with a '96 303 SR-1 Formula with 7.4L's/Bravos. Boat has between 400 - 500 hours on it total. Motors were pulled a couple of years ago and built up to 465 HP by Baker Eng. At that time, Imco hydraulic steering was added. We pulled both drives yesterday to service them. While the drives were off the boat, I grabbed both bell housings and moved them both vertically and horizontally to see how much play was in the gimbal ring. On the starboard side, I could move the bell housing up and down quite a bit and you could hear it clunk. There was also slop in the side hinge pins where you could make them clunk. On the port side, I could not really move the housing up and down and there was just a little bit of movement in the hinge pins.

My question is two part. First, was my grabbing the bellhousing with the drive off and moving it around an OK method of checking the health of the gimbal ring. Second, how bad off does the starboard side sound? I did not attempt to mess with tightening the nuts on the u-bolt to see if it took some of the play out for fear of snapping the u-bolt. My friend asked how bad the starboard side was and my feeling is there is too much play but I wanted to get some expert opinions. Thanks.

 

[MOBILEMERCMAN]

First the up and down is set by the nut on the upper swivel shaft inside the boat. Usually when the distance increases and the ring falls it is from corrosion on the ring. Generally you need to remove the assy or cut the access holes to tighten. The clearance is something like .025. Maybe less I would have to look it up.

Second the hinge pins should have no play. Slight side to side parallel to pins only. None in and or out up or down.

The u -bolt torque is light at 23-25 lbs. That wont fix it.

When the ring settles it tends to mis align the cross bearings and adds a side load to the gimble and input bearings. When the hinge pins wobble loose a bell housing { the part the drive boats to } failure is immanent. I am sure you have heard the stories of drives breaking off and hanging by cables.
I would be most concerned about the hinge pins.

If your transom assemblies need major repair buying new assemblies are worth considering. They show up priced right from time to time

 

[Knot 4 Me]

Thanks for the reply, Jim. Yeah, I figured the swivel shaft nut is what set the up and down play. I didn't know if maybe the nut was loose, the washers have worn (13, 15 in the diagram), or if the housing itself has worn and that is where the extra play is coming from. You could really see the bellhousing move up and down when I pushed on it. Seemed way to loose to me. As for the hinge pins, yes I could move them side to side parallel but I could also feel up/down and in/out movement in them. If there should be zero movement in them, then you have answered my question that there is too much play. The scenario you describe above with the drive breaking off is what has me concerned. You mention input bearing load. I assume you are referring to the driveshaft input bearing?

Thanks for your help. I will recommend he has the starboard side addressed immediately. If the assemblies are in good shape, can the bushings be replaced to remove the play in the hinge pins?

http://www.mercruiserparts.com/Show...&bnbr=70&bdesc=GIMBAL+RING+AND+STEERING+LEVER

 

[MOBILEMERCMAN]

The bushings can be changed, but I have found the threads in the bellhousing are often the worn part. There are a few different bellhousing out there. The early with threaded hinge pins, the late with threaded pins and a inset Stainless washer, and the HP pins. The early the threads wobble and junk the bellhousing. Don't bother trying heli coils. Make sure you get the bellhousing with the washers. The second seems to hold up pretty well. The if the threads are good and the bushing whole is not egg shaped you can re bush with success.

On the gimble ring settling. I have found the ring erodes the swivel is steal and the ring is aluminum. .. I recently did a dropped ring. After drilling the access holes I was able to replace the upper swivel shaft and bushings and reuse the ring. I replaced the shaft because the seal surface was pitted and would not make a good seal surface and the seal was gone. If the ring and the bellhousing need replacement by chance a complete assembly may be better spent money.

 

[MOBILEMERCMAN]

This pic shows the late bellhousing with washer

http://www.mercruiserparts.com/Show...476.png&inbr=11296&bnbr=90&bdesc=Bell+Housing

 

[Knot 4 Me]

Thanks so much, Jim. I do want to double check the amount of hinge pin play. Can this be done with the drive on? Can I just grab the drive and start moving it around checking for play or will the tie bar and steering rams give too much resistance? Should the bar and the rams be removed first and then move the drive to check for play?

 

[MOBILEMERCMAN]

You can check it assembled . You just need to use more muscle. Take the pin covers off to see if it wobbles or moves in the bushing.

 

[Knot 4 Me]

Will do. Thanks again! By the way, the serial numbers are:

O.D. 0F814903 0F814906
TRN. 0F860644 0F860646

 

[Blue Thunder]

First the up and down is set by the nut on the upper swivel shaft inside the boat. Usually when the distance increases and the ring falls it is from corrosion on the ring. Generally you need to remove the assy or cut the access holes to tighten. The clearance is something like .025. Maybe less I would have to look it up.

.002-.010 on the gimble clearance setting.

I'm pretty sure the u-bolts are 50-55 ft-lbs not the 23 mentioned.

 

[MOBILEMERCMAN]

You are likely correct on the gimble clearance. I haven't taken the time to look . I thought it might be less. But I can assure you that cheap metal 3/8 u-bolt won't take 50 lbs. It was misprinted in the manual in the past. I have broken one before. No fun doing the ring install twice.

Sorry, I did not edit your post. I hit edit on my screen by accident.

 

[Blue Thunder]

I have always torqued them to 50. I just rebuilt two and they are at 50. Never a problem. The standard toque spec on a 3/8"-16 bolt, grade 5 is 35-40 so 50 does seem rather high unless it is a grade 8 strength. Then it would be close at 50-55. BTW, that is still the merc spec. I'll post it up.

 

[Blue Thunder]

Here you go..... ft-lbs and newton meters. Ubolts are 53ft-lbs. Maybe this spec is for new ubolts only or ones with no material loss due to corrosion.


Torque Specifications
DESCRIPTION lb-in. lb-ft Nm
Shift Cable Core Wire Anchor Screws 20 2.3
Hose Clamps 35 4
Trim Wire Clamp 95 11
Hinge Pins 150 203
Bell Housing Studs
Steering Arm Nut
50 68
Rear Engine Mounting Bolt 37 50
U-Bolt Nuts 53 72
Transom Stud Locknut 25 34
Pivot Bolt
Sterndrive Attaching Nut
23 30

 

[MOBILEMERCMAN]

Dave,
I know what the manual says. You are quoting it correctly. I have been round and round with this before. At some point you will break one.

 

[Blue Thunder]

No I won't because I won't go that high any more. I would recommend if you are only torquing them to 20ft-lbs you loctite the threads or use nylon inserts. You won't have enoungh fastener stretch at that torque for them to stay tight on thier own.

Thanks for the warning. I can imagine the aggrevation created if one of these snaps on a installed asembly

How you know my name?

 

[MOBILEMERCMAN]

No I won't because I won't go that high any more. I would recommend if you are only torquing them to 20ft-lbs you loctite the threads or use nylon inserts. You won't have enoungh fastener stretch at that torque for them to stay tight on thier own.

Thanks for the warning. I can imagine the aggrevation created if one of these snaps on a installed asembly

How you know my name?

Dave,
I put red loctite on everything. If you contact Mercury they will likely recommend 23-25 lbs. It is the only mistake in their manuals I am aware of in over 25 years.

I checked your profile.

We appreciate your input. Thanks

 

[Knot 4 Me]

I didn't mess with the nuts on the u-bolt due to the age of the boat and knowing it really wouldn't solve anything but could create a big problem. I would think those nuts really shouldn't be messed with after initial assembly. Anyway, thanks to everyone for their help. The boat goes into the shop at the end of the week to have our friend who is a certified Merc tech take a look at it and if need be, pull the motor(s) and replace what is necessary.

 

[MOBILEMERCMAN]

There are two ways to attend to it. You can service it with out pulling motors.

 

[Blue Thunder]

Dave,
I put red loctite on everything. If you contact Mercury they will likely recommend 23-25 lbs. It is the only mistake in their manuals I am aware of in over 25 years.

I checked your profile.

We appreciate your input. Thanks

Ok, Jim. Thanks for the poop on the ubolts. I still wonder why yours fail and will consider that further. My guess is corrosion or unequal/improper torquing. The surface prep of the torque surface and lube applied to the threads (or lack of) makes a world of difference in actual torque values Where do they snap? At the threads?

 

[MOBILEMERCMAN]

It has a number of years ago. it broke at the threads. It was not brand new but looked good. It is just stainless. A friend of mine broke one too. The Race boat I used to run had broke on at one point. It had the lower number torque value etched on near the nuts to ensure no one broke another one.

 

[Blue Thunder]

It has a number of years ago. it broke at the threads. It was not brand new but looked good. It is just stainless. A friend of mine broke one too. The Race boat I used to run had broke on at one point. It had the lower number torque value etched on near the nuts to ensure no one broke another one.

Good info, thanks.