1996 OMC Cobra / Volvo SX gaskets

[Lpgc]

Yes, you need to remove the drive again. This time I would make a cart for the drive. Set up the height so you can trim the drive horizontal and you can raise/lower the front of the trailer so the drive sits on the cart. Then you'll find it's very easy to remove and re-install. On the engine mounts I would try to get both sides at equal height, then adjust both up or down until the alignment tool slides right in. With grease on the end of the alignment tool, if you see deeper spline marks on top of the tool, raise the front mounts. You don't need to mess with the rear mounts.

The nuts on top of the motor mounts are meant to be lock nuts to prevent the lower nut from moving.

Thanks. I'll try to get around to removing the drive again over the next few days. The main reason I'm concerned about the rear mounts is because I removed and refitted this engine a couple of years ago, I remember having some confusion about how the rear mounts fit together.

When I've removed the drive will it be OK to leave it on it's side without dropping the gear oil? I'm thinking too much gear oil might move up to the upper end of the drive but it'll be months before I use the boat again so even if that happens the oil will drop back to where it's supposed to be when I reinstall the drive.

The top nuts on the front mounts are locking nuts, the nut(s) below don't seem to be locking nuts... But there are 2 nuts below on the port side and only 1 nut below on the starboard side - maybe the starboard side dropped if the 2 nuts below are supposed to be torqued together to lock each other?

 

[Lou C]

Agreed Horigan's way is the best way. Build a cart, or modify a motorcycle jack to make the drive R&R easier, then get the alignment right, then you're good and won't have to worry about stressing the coupler due to the alignment being off.

 

[Lpgc]

A cart would be best but I didn't struggle when I used the ratchet strap. I'd need to buy/make the cart so I'll probably try using the ratchet strap again next time. Another thing I like about the ratchet strap is it has a bit of elasticity, making it possible to make minor angle adjustments just by slightly pushing on the drive.

 

[Lpgc]

I removed the drive again, it took some effort to remove it.

The alignment tool still slides in easily and is still giving equal spline witness marks.

I changed the engine coupler when I rebuilt the engine a couple of years ago because 1. I thought the splines in the coupler might've been a bit worn and 2. The rubber in the old coupler wasn't seated against the rear of the unit in one area.

I still have the old coupler and tried putting the end of the alignment tool through it, it's not a tight fit on the alignment tool but witness marks do change a bit if I put some sideways force on it when I push it in and pull it out. Then I tried the old coupler on the drive input shaft splines, that is a much tighter fit. So I'm not convinced that checking alignment using the alignment tool is likely to give accurate results because it doesn't seem tight enough in the coupler splines to give accurate enough results. Even if I put a lot of sideways force on the alignment tool going into / out of the old coupler it's difficult to see much difference in the witness marks.

I read somewhere that it could be possible to have the engine out of alignment but it seem to check OK using the alignment tool because the alignment tool only goes through the gimble bearing and into the coupler (and the gimble bearing axis can move) which is only 2 points, where-as it's different for the drive because the input shaft of the drive also has the rear fixed in one position where the shaft enters the drive at the other side of the Ujoints which is 3 points. Do you think this could be what's happening in my case? I'm thinking maybe it would seem to line up OK using the alignment tool anyway because as the engine moves while I'm adjusting its height the gimble bearing can just tilt to allow the alignment tool to go through it and into the coupler? If so, is there another test I could do such as check the position of the rear of the alignment tool relative to the 6 drive mounting studs?

 

[Lou C]

You raise some very good questions but I don’t know the answers to most of them not having had to adjust the alignment on my boat. I would however, rotate the engine 90* from where you started and continue to where you were at the beginning (0*, 90*, 180*, 270* and 360*) and check again, Do this till you end up where you started checking alignment each time. I would be surprised if it was the same all 4 times it can be checked.
The other thing is that I/Os use what’s called a double cardan u-joint assembly, this allows somewhat more movement than if it were a simple single u-joint driveshaft.

 

[Lou C]

I can't wait to hear your theory behind the mystery of how it unwound itself!

 

[Lpgc]

I think it must just be engine vibration that made the starboard front engine height adjuster nut wind down.

I haven't rotated the engine manually but did crank it using the starter motor before I removed the drive, so chances are that the coupler had rotated to a different position compared to when I fitted the drive.

I've just posted this (below) as a comment on one of Michael Romer's YouTube engine alignment videos, would appreciate your and other iboats forum users thoughts on this too...

I rebuilt and refitted my engine a couple of years ago (1995 Ford 5.0 OMC Cobra / SX collaboration), obviously I removed and reftted the drive at that time. I recently fitted a new gimble bearing, alignment checked OK using the alignment tool and checking spline grease witness marks but it was difficult to refit the drive. I intended on testing the boat with the new gimble bearing one time before winterising but decided just to winterise instead. Working on the engine during winterisation I noticed the starboard side front engine mount had wound down so the engine was sitting low starboard front.. which begged the question why did alignment check OK and how did I manage to refit the drive. I wound the engine height adjuster nut back up but decided to remove the drive and check alignment again, it still checked OK despite having just raised the front starboard side of the engine over an inch. Then as a test I partially inserted the alignment tool and used it to adjust the bevel angle of the gimble bearing, as expected the alignment tool wouldn't fit into the coupler. So I adjusted the bevel angle of the gimble bearing again and now it slots into the coupler again no problem. Seems to make a bit of a mockery of the alignment process? But I have noticed that when the alignment tool is all the way in it seems like the angle of the alignment tool through the gimble HOUSING (metal hole that the gimble bearing goes in) points down at the rear. If the shaft points down towards the rear won't it mean that the shaft will be too low at the rear for the U joints to be in line? It seems I could adjust the engine front mounts to various positions, then by adjusting the bevel angle of the gimble bearing the alignment tool would fit OK with minimal resistance... But do we also need to be concerned about the angle of the shaft through the gimble housing? Should the alignment tool be parallel with the walls of the gimble housing? I am thinking that if it isnt parallel then the drive input shaft rear of the U joints will never be inline with the shaft forward of the U joints... Is that correct and if so would it be a problem? Since my alignment tool seems to point slightly down at the rear when it is inserted through the gimble bearing and into the coupler, should I lower the engine at the front (and partly insert the alignment tool to adjust the bevel / gimble angle) so that the alignment tool fits easily through the gimble bearing and into the coupler when at the same time the alignment tool is parallel with the walls of the gimble housing? It occurs to me that the big difference between the alignment tool and the drive input shaft (other than the alignment tool not having splines or U joints) is that the alignment tool only has to align with 2 components (the gimble bearing and the coupler) while the actual input shaft has to go through the gimble bearing, into the coupler and is also has to be at a fixed position at the rear so that's 3 points versus 2 points. It's a lot easier to get 2 points aligned than 3. How much do we need to be concerned about that 3rd / rear point also being aligned?

 

[Lpgc]

Since my last post 1hr10minutes ago I've refitted the drive!

This time it went on really easy, I moved the drive over to the back of the boat, got the input shaft through the gimble bearing, got the gear shift cable into its hole, used the ratchet strap to lift and align the drive, it slid right in no problem at all.

Before fitting it I spent a bit of time rechecking alignment and moving the angle of the gimble bearing using the alignment tool. But I don't know what made the biggest difference between this time when it went on easy and last time when it was a struggle... It could be because I raised the engine at starboard front / maybe had the Ujoints in a different positon / maybe because by moving the axis of the gimble bearing it helped free it off or align it better / maybe a combination of things.

I'm happy alignment is OK now but I would still be interested in answers to what I said in my last post about whether the input shaft has to be aligned at 3 points not just 2 points.

As it stands now the front engine mounts are set to the same level as they've been for at least the last couple of years and iIrc I didn't change the position when I refitted the engine a couple of years ago. But the locking nuts on top are almost as high as they could go before the nylock would come off the top of the stud... So I couldn't really get the engine any higher at the front even if it needed it unless I changed/modified the engine mounts.

I had another scare when I used the tilt/trim to lift and lower the drive... When the drive was at the lowest position the trim guage read it was half way up. I used the tilt/trim to lift it all the way up and shut it off when it squeeled as usual, then thought I'll test the gauge by lowering it fully again. When the drive got to the bottom it made a short squeel sound but then stopped working, pressing the trim buttons had no effect. I checked the 2 pin trim connector on the engine (which I've had a problem with before) but that seemed OK. Eventually found that the circuit breaker on the engine had tripped, reset it and the tilt/trim works again.

 

[Lou C]

Interesting questions!
The basic alignment is lining up the gimble bearing to the coupler which as you say is 2 points that have to align. Now of course there’s the other end of the driveshaft which terminates in the upper gear housing of the outdrive. I think the issue of a 3rd point of alignment is why the driveshaft uses a double cardan ujoint design rather than a single ujoint design, the double cardan tolerates greater angular offset of the driveshaft than a single ujoint design. This is because any angular difference between the end of the shaft in the coupler and the end of the shaft supported by bearings in the upper gear housing is split between the 2 ujoints in the double cardan design to the offset of each joint is half of what would be seen with a single ujoint design. This allows the driveshaft to run relatively smoothly even with much greater angular changes that are required for steering and trimming the drive. Double cardan designs are often used with lifted 4x4s for this same reason; lifting a 4x4 puts the driveshaft at more extreme angles vs the flanges at the differential housing and 4x4 transfer case.

 

[Lpgc]

Interesting questions!
The basic alignment is lining up the gimble bearing to the coupler which as you say is 2 points that have to align. Now of course there’s the other end of the driveshaft which terminates in the upper gear housing of the outdrive. I think the issue of a 3rd point of alignment is why the driveshaft uses a double cardan ujoint design rather than a single ujoint design, the double cardan tolerates greater angular offset of the driveshaft than a single ujoint design. This is because any angular difference between the end of the shaft in the coupler and the end of the shaft supported by bearings in the upper gear housing is split between the 2 ujoints in the double cardan design to the offset of each joint is half of what would be seen with a single ujoint design. This allows the driveshaft to run relatively smoothly even with much greater angular changes that are required for steering and trimming the drive. Double cardan designs are often used with lifted 4x4s for this same reason; lifting a 4x4 puts the driveshaft at more extreme angles vs the flanges at the differential housing and 4x4 transfer case.

I can see how 2 U joints are much better than 1... But still for things like driveshafts on cars with independent suspension CV joints are used these days instead of U joints (or even 2 U joints) - I think the reason for that is because even 2 U joints cannot act fully like a CV (constant velocity) joint, they may allow steep angles between input and output, be able to handle a lot of torque and off-plane (input and output might be parallel but not in line) situations better than CV joints but won't keep velocity the same as well as a CV joint, and while a CV joint doesn't need to move in/out when compensating for being slightly off alignment I don't know if a double U joint would need to move one end in/out at the same time as compensating for misalignment.