4.3L mount failure scenarios

[RobertGary1]

I have a 4.3L in my 2003 185. I assume the mounts are similar to automotive mounts in that if they collapse the engine drops. Wouldn't that break the coupler? So even if you checked alignment twice a season you're still just one random mount failure away from a coupler failure? Or is there some other mechanism I'm not seeing that keeps this from commonly happening.


Curious how common coupler failures are.

-Robert

[706jim]

While a collapsing mount won't "break" a coupler, it will cause rapid wear due to the side load on the splines. This is a good reason to periodically check drive/coupler alignment as coupler replacement usually means pulling the engine.

[businessgetmoney]

Every boat mount i have seen are solid studs with a nut on bottom passing through block mount, then nut on top. They arent a rubber cased mount like automotive. Cant see any way they could ever fail. I think a stringer would rot and pull out before the mount would

[MonteVista]

Every boat mount i have seen are solid studs with a nut on bottom passing through block mount, then nut on top. They arent a rubber cased mount like automotive. Cant see any way they could ever fail. I think a stringer would rot and pull out before the mount would

+1
I don't see how this is possible. If anything minor changes may occur over time and you should be checking the alignment each time you pull the outdrive off for maintenance. On the other hand, having gone through that just recently I can tell from experience that a perfectly aligned engine/drive improves engine performance.

Good luck

[Pcpete]

Engine mount failure, if it happens is most often collateral to some other event. Like has been said, when the drive is off for service, check the alignment. I had a pair of 4.3’s on my previous boat. In the 15 years I used them I never had to adjust the alignment. The only problem I had with the gen 2 alphas was the ujoint bearing caps were not properly lubricted before installation, no zerk permanently lubed style, and they had to be replaced after 900 or so hours.

[driz]

Every boat mount i have seen are solid studs with a nut on bottom passing through block mount, then nut on top. They arent a rubber cased mount like automotive. Cant see any way they could ever fail. I think a stringer would rot and pull out before the mount would

Oh that 4.3is special. My 90 has those fluid filled mounts. Something to do with vibration abatement. They don’t look the strongest for sure. Mine are backed up with slightly over length cables with balls or slugs on both ends threaded through plates, one on each side. I recall GM having a similar loop style rig in response to powerful V8 mills snapping motor mounts. I guess they kept they kept engines from wandering too far, tugging on throttle linkages and sending people for a wild ride.

[RobertGary1]

Thanks for all the responses! Any recommendations on where to get the alignment tool? I see a lot out there with a lot of variability in price. Some come in kits with tools to replace the bellows and gimble but I'm not assuming I'll need those.

-Robert

[MonteVista]

It is a simple, splined hub. The one I had used had a T-sghaped handle bar for easier use but that is not essential. Look at the attached video. The idea is to be able to insert/remove the tool in/out without needing to apply too much pressure in either direction.

https://www.youtube.com/watch?v=x-g6fFYtDLw

Good luck,

[builderdude]

The mount base is insulated from the stud with some type of rubberized urethane, yes they do wear down over time.

[RobertGary1]

Is this $32 + free shipping alignment tool too good to be true? Are there good and bad versions of the tool?

https://www.ebay.com/itm/Alpha-Bravo-OMC-Engine-Alignment-Tool-For-Mercruiser-boat-Marine-USA-made/270940004316?hash=item3f15485fdc:m:m0E5R7VHJskc84tUwPuwYaQ:sc:USPSPriorityMailLargeFlatRateBox!77070!US!-1&vxp=mtr

-Robert

[builderdude]

Looks just like the one I use.

[706jim]

You could make one on a lathe. Probably take about an hour by the time you machined it and cleaned up. Easily worth $100 if you farmed it out. So to me, this is a good deal at thirty bucks.

[RobertGary1]

Should the tool have splines on the end? These don't. How do they fit into the coupler?

-Robert

[builderdude]

No splines needed, it fits into the ID of the coupler splines.

[MonteVista]

No! It should have splines. The whole point of the alignment tool is for it to act as the horizontal shaft from the drive unit going into the coupler. It should be an exact image of the horizontal shaft, in terms of number of splines, their thickness, etc. As you insert the alignment tool, it will go deeper and deeper into the coupler and if the coupler and the gimbal bearing are perfectly aligned there won't be any friction around their inner surfaces and the tool will go in/out easily. Otherwise, the tool will go into the coupler at a slight angle and friction will make it harder to insert or retract. That is how you can tell if alignment is good.

Good luck