Oh dear... noisy engine... possibly engine alignment

[nigel]

Oh dear... noisy engine... bad alignment?

I just finished replacing the manifolds on my 4.3L s. Whilst they were off, I torqued-up the rear engine mounts and did a load of other maintainance on everything else I could reach at the back of the engine.

Starting up one of the engines now there is substantially more noise than there should be! - You can't hear it with the hatch open really, but when closed it sounds like the exhaust is -much- louder than normal. Actually I don't think it is, or I'd hear it with the hatch open - The noise seems to be more a vibration of the whole of the rear of the boat which you can dampen by standing on various panels...

Now... I -suspect- I might have now mis-aligned my engine. The rear mounts were quite loose on that engine. Putting the proper torque on these mounts will have shifted down the drive coupler, I'm guessing/wondering...

So my question is - has anyone had a badly aligned drive? What kind of noise would I expect to hear?! - Will I have damaged anything, given I ran the engine for 40 mins? - but didn't go anywhere - only at the dock.. Or has anyone any other ideas what I could have done?

Cheers,


Nigel.

 

[fwebster]

A misaligned coupler makes a rumbling noise. You need to figure this one out before you run the engine anymore. Changing a coupler is an expensive repair since the engine must be removed from the boat to do it

 

[nigel]

Thanks Frank.. Would you expect it to be pretty loud? - I think I'll get the boat liftied out and pull the drive - so I can get an alignment tool in there...

What kind of noise /how would I know if I'd wrecked the coupler?

I've also got a watery + oily leak down there somewhere I've had for a while... Can't work it out though.. Not related, I don't think, as its done this for a couple of years and I'm putting off the engine-out job..

 

[BonBini]

Is it possible that you were cranking on the alignment jack bolts? I would think alignment would have to be off a long way to make the noise you describe. It does sound like pulling the outdrive and checking alignment is the thing now to do. That way you can check and service the universal joint too. Might be a good idea to do both engines, that way your done with it.

Hope all turns out well.

 

[fwebster]

Nigel,

You didn't mention the water leak !

IF you have had a water leak from an un-explained source for a while, you most likely have a bellows leaking and now, a rusty gimble bearing since the water works its way from the bellows thru the gimble bearing and into the boat. All you will see inside is a slow seeping under the drive so it is difficult to identify the source of the leak. My bet is that when you lift the boat out of the water you will find a crack or hole in the bellows. And, a bad gimble bearing makes a horrible and sometimes loud rumble when the engine is running.

If all you did was tighten the top nuts on the motor mounts, that should not have changed the alignment sine the nuts under the bottom control the height of the engine. So, now with the leaks, I doubt you have a coupler problem, however, the drive has to come off to service or replace the bellows and gimble bearing, so I would realign the coupler while you have the drive off.

Good luck with it..........

 

[wakeup 19]

May also want to check the flappers in the exhaust line, they can make some noise.
When you turn the steering wheel does the sound change? If so it is most likely gimbal and you need to change that as well as bellows as previously mentioned. Try mirrors for areas you can't reach. I had a leak in the "bullhorns" that caused me some issues as well. lots of light as well. Good Luck

 

[nigel]

Thanks for your replies...

I changed the gimbal bearings last summer and the bellows were fine.. I also wonder if I have a leak in the bullhorns or gasket but what makes me think its something else is that there is always oil in there.. When I changed the manifolds I checked the flappers and they too were fine.

I don't think its an exhaust issue though as its no noisier or quieter if I open the throttle or close it off - the noise level depends on the engine speed..

What are the alignment jack bolts, by the way? - I was pretty confident I was torque-ing down the rear mounts.. Are there other alignment bolts than the front engine mounts??

Cheers,


Nigel.

 

[nigel]

I also meant to add... it only leaks when the engine is running - the rest of the time its dry as a bone...

 

[BonBini]

"What are the alignment jack bolts, by the way"

rep: Your forward eng mounts have a threaded rod incorporated so one can raise or lower the engine as needed when aligning. Frank referred to these same bolts when he mentioned...."If all you did was tighten the top nuts on the motor mounts, that should not have changed the alignment sine the nuts under the bottom control the height of the engine".

It was a little difficult for me to fully grasp what you did with your first post description.

What I'm gathering now is: you snugged up the rear engine mounts at the flywheel to transom plate area. Then fired up the engine and had this noise/vibration that is consistent with engine speed. Not knowing if the vibration was pre existing to the engine mount service or not. The water/oil leak issue is a whole other problem.

Some others have mentioned the Gimbel Brg area and I have to agree with. If raising and lower the drive changes the noise/vibration then your in the right area. Also if greasing the Gimbel Brg when its running changes the symptoms the I would think the Brg must be the culprit.

I'm sure you know when the drive is raised all the way up in trl mode It Will Vibrate and Rattle like a MOFO. Just Sayin!

Hang in there......

 

[nigel]

I dropped the front mounts down a turn this morning before starting up and I percieved the sound to be quieter... didn't rev it up though to check at decent revs in case I was making it worse.

Anyway - gently drove over to the crane and got lifted out. I've taken the drives off this afternoon and both UJ bellows are dry as a bone and bearings appear OK.. So next plan is to just perfectly align everything and see how it goes when I drop it back in.

Actually that engine is somewhat higher on the left than the right - always has been - one front mount was missing for a few years before I noticed! Rear mounts, although now tight, are not evenly high relative to the transom bits either (which I guess is good given the block isn't 100% level or I'd be bending the motor!)..

The drive came away from the bell housing very easily - shaft not stuck in the coupler at all.. But how can I tell if the coupler is still in good condition and not just all floppy on the back of the engine now? - and hence even if misaligned not stopping the shaft coming out easily?

The leak - might - be the power steering cooler, actually - As its the port engine and the steering pump isn't doing anything, I'm wondering if I can just bypass the cooler and feed the outlet of the pump back into the inlet <- anyone know if I can do this? Does the pump itself generate significant heat when not under load?

Cheers for your thoughts once again...


Nigel.

 

[BonBini]

nigel: There is an alignment tool that inserts from the gimbel bearing end. Checking the tools fit with the engine in several different rotations will not only check engine alignment but also check the couplers runout. The other area of the coupler that needs to be inspected is the drive splines. Look closely at your shafts for spline wear and look up into the coupler too. A dummy shaft is handy to hand check for sloppy coupler splines, but just isn't something the average boater has laying around.

I think if I were you at this point and something wasn't jumping out at me, I’d fire the engine up with the drive off and see how it sounds. Although the engines water pump will be fine running with no water for a short 10 secs, I probably would pull the belt anyways... just a thought.

Edit: Make sure your not missing some sort of fiber washer or some type of dampner componant from those rear mounts you originally tightened!

 

[nigel]

Any one know how much rotation there can be in an engine against the rear mounts before its a problem? - Both my engines were not very horizontal in the engine bay and they are also (now) not aligned 100% with the angle of the transom plate... So one rear mount sits slightly higher than the other.. even when torqued down.

Is this critical? - I can rotate the engine at the front mounts to get the rear mounts to be -about- the same - measuring with the not-so-accurate feeling-round-the-back-with-my-fingers method.. That good enough? - Or do I need a hoist on the front to take all weight off the front mounts to do it properly? (which I don't have to hand..!)

I can align the coupler perfectly but am worried about uneven stresses on the mounts.. Obviously the rear mounts flex a bit with the engine torque..

Cheers,


Nigel