Engine shaft alignment

[timjet]

I was out the other day and while doing my post run inspection I found my port engine mount not looking right. The first picture shows the 2 locking nuts about 1/2 " above the mounting plate. I don't know how long it had been like this, maybe since I bought the boat 3 years ago I can't say.

Thinking this does not look right I tighten the nuts so they were tight against the mounting plate, the second picture shows how they are now.

I ran the boat for about 2 engine hours with no issue. Then when I tried to use the boat 6 weeks later I could not get above 1500 rpm and got heavy black smoke. Back at the dock I did some diagnostic work and eventually determined that the shaft would not turn easily. The diver that I hired said the prop shaft where it enters the hull does not go into this hole through the center but is off to one side slightly. There is a standard stuffing box on the shaft just inside the boat. He also said he could not turn the shaft while he was under the boat, but with difficulty could turn the shaft if he grabbed the prop to do so. The other shaft he said turns easily.

So I'm thinking that when I tighten those engine mount nuts I did something to mess up the alignment.

Any suggestions on where to start to fix this?

The third picture shows the stuffing box.

Thanks guys.

 

[sunchaser]

I suggest you engage a GOOD yard experienced at shaft alignment. Willy nilly adjusting mounting bolts is not a good idea.

 

[Phil Fill]

Shaft alignment are done with the boat in the water. So if you do not know how too do an alignment its best to hire someone. Most diesel mechics know how. I always am there to watch and learn how its done. Its not that hard. At least I would loosen the bolts up so the shaft turns like the other one.

 

[Shoalwaters]

Tim, I suggest you remove the 6 bolts that hold the shaft flange to the motor flange. Persuade the shaft backwards by about 1/4" unitl it clears the lip on the motor flange that holds it centered. The flanges will either remain aligned (sharing a common axis) when you separate them, or the shaft flange will spring "sideways" because it was being forced into alignment. At least you now know if you have an alignment problem or not.

 

[Brooksie]

Find out how to do a proper alignment or hire someone before you do some permanant damage to your driveline or hull.

In reviewing your first picture, the lower nut (under the plate) should have been raised up, not the upper ones tightened down. As a result you are seriously out of alignment. Also, you are better off with the double nuts under the "plate" and an elastic nut over it. Things fall down not up.

 

[Nomad Willy]

Aligning an engine to a shaft is'nt complicated. But it requires patience and considerable time w wrenches.

How to =
Adjust the engine mounts (all 4) so that when the propeller shaft is centered in the stern tube or stuffing box hole the shaft flange is parallel to the flange on the end of the gear. That's all there really is to it.

BUT,
Raising or lowering the engine is easily done. Yawing the engine is not so easily done but fortunately yawing the engine is not usually needed if the alignment was good after the engine installation and has not been changed. It most likely won't need adjustment. But if you do use 2 corner mounts as jacks and raise the whole engine up by running the lower nuts up. Then run the other corner mount lower nuts down. Now those corner mounts can be loosened from the engine beds and moved around limited only by the clearence in the mounting holes. Hopefully that will be enough to bring about the necessary change in lateral position to get the engine aligned. With loose engine bed screws I have in the past used a drift and hammer to "tap" the base of the mounts over. If the upper nuts are loose you can easily lever the engine up a bit and tap the mounts this way or that.

First align the engine so the gap (feeler gauge) is the same at the top and bottom of the coupling flanges. Then check the sides. Usually they will be the same. Then if the shaft is centered in the stern tube or stuffing box you're good. Remember that when you adjust at one end of the engine you'll change the height of the gear flange and if you adjust all 4 mounts up or dn the same you'll change the height of the gear flange. Think ahead before you change adjustment and see if your change accomplished what you thought it would.

Engine mounts should be changed from time to time. Consult w their maker for life expectancy. Some are amazingly short .. like Yanmar. You'd think they were trying to make more money selling engine mounts.

If you need or want to change engine mounts use corner mounts to jack the engine up. Adjust another corner mount down and use the top nut to pull that corner down. The opposite corner will be high enough to remove the engine mount completely ... and insert a new one. Takes some time but it's not difficult depending on space available to see what your'e doing and swing your wrenches.

What probably happened to you timjet is that the lower nut became loose and vibrated down. Then when you tightened down the top nut you changed the adjustment radically. I'd check your other mounts carefully for damage .. especially the mount on the other corner.

 

[timjet]

What probably happened to you timjet is that the lower nut became loose and vibrated down. Then when you tightened down the top nut you changed the adjustment radically. I'd check your other mounts carefully for damage .. especially the mount on the other corner.

Thanks Eric and all who participated. Yes I hope you're right that the bottom nut vibrated down and I threw it out of alignment when I tighten down.

I hope this out of alignment issue is the cause of my severe smoking and low rpm issue. It has to be fixed for sure but at the same time the engine ingested some salt water, so I'm trying to track down the cause of the smoking.

My adventure with this issue is fodder for another tread. Some lessons have been learned.

 

[C lectric]

Tim,
The photo , 1st, shows 4 threads of the stud above the twin nuts. Jack it back up to that level. That should get you back very close to the original setting. It will still need to be checked fully for alignement as pointed out but at least that should free up the shaft bind and unload the other mounts.

As Eric suggested you will need to check the other mounts, particularily the opposite unit.

 

[RickB]

It has to be fixed for sure but at the same time the engine ingested some salt water, so I'm trying to track down the cause of the smoking.

Ahh, the rest of the story.

 

[Trawlerpeople]

My dad used to say "if you change something and bad things start to happen, put it back the way you found it".