Bent strut and drive train maintenance

[tiku]

Hi!

I decided to tackle some drive train maintenance this haul-out season. On the to do list are:

-changing stuffing box hoses
-dealing with bent strut
-replace strut bearings
-etc...

I ran into a problem with my port engine and more specifically with the strut. As you can see the axle is not really in the center and the bearing has worn quite heavily.

Another clue as to something is wrong is where the axle enters the hull. There is an area, roughly 10 cm long where I have nice shiny metal. In other words the axle is touching the hull. Lightly but still, it's not right.

The props are off (it was another battle, read more from the blog) and the starboard strut is fine and the bearing shows no uneven wear but I'll change it anyway.

Tonight I disconnected the coupling from the transmission and I was wondering if the axle is going to shoot to some direction due to the bent strut but no, it seems to be dead on.

As you can see, we are talking about picture perfect alignment here.

So this leads me to wonder how is it possible? The strut is bent, I can see it with my eyes and the axle is eating into the strut bearing but still the coupling end shows no misalignment and during the season there were no vibrations.

Should I proceed with the strut? Drop it off and have it straightened or buy a new one? Or am I killing the drive train softly if I just reassemble it "as is" after doing the maintenance.

Logic says to go the long way, but I'm wondering why the axle is not showing any misalignment in the coupling end?

To my knowledge there is no bearing in the "axle tube" and my stuffing boxes are of the hose type so they don't really offer support...

 

[Larry M]

Have you pulled the shaft to make sure that it is straight? And how does the shaft look at the front of the strut/cutlass bearing? I'd pull the shaft then do an alignment check with string or laser from the coupler through the strut.

We had a bent strut on our sailboat. It was easier/cheaper to repair than to replace since a replacement would have to be cast.

 

[tiku]

Not yet, the coupling flange is waiting for tomorrow in a bath of release oil. It was enough trouble today to punch out the locking pin, undo the bolts and get the flanges separated. I will drop the shaft anyway and have a closer look at it.

To me the front of the strut/bearing does not look as bad as the rear, I will get a better look when the shaft is out. It's just that I was so sure that there would be a huge misalignment issue, but no....

In case anyone is wondering, in Volvo's setup the pin goes through the axle and can be punched out with a 6mm punch...

 

[obthomas]

Use a spacer just smaller in diameter than the shaft and recouple the flanges with longer bolts and make up the bolts and press the shaft out of the coupling.

 

[RickB]

Use a spacer just smaller in diameter than the shaft and recouple the flanges with longer bolts and make up the bolts and press the shaft out of the coupling.

Another word for spacer is socket.

 

[psneeld]

just because the shaft is aligned with the motor doesn't mean a thing if everything is not in the right place for the struts, stuffing tube, etc....

First line everything up roughly then before aligning the engine...see just how much resistance is on the shaft from the cutlass bearings...if a lot...then the strut may have to be realigned.

 

[C lectric]

Also get the shaft itself checked. It could have a small bend from whatever bent the strut. Maybe not but find out.

 

[bglad]

You may be able to use a large pipe wrench to straighten the strut into alignment so when you install a new bearing it won't be in a bind. Before you do too much you need to make sure you can put the engine where it needs to go after you realign the strut and propeller shaft in the hull. Aligning the prop shaft in the log is nice but doesn't really help anything. Especially if the engine can't be moved to mate up with the shaft coupling without hitting the hull bottom, stringer or deck.

 

[Tom.B]

We are doing much of the same maintenance this winter too. We have already diagnosed a bent shaft and we plan on a complete replacement. I certainly wouldn't say that a bent strut isn't the problem, but IMHO, that's a pretty hefty piece. If you have yet to do it, you might want to have a pro come help you diagnose it before you start going at it with brute force.

 

[Forkliftt]

Great approach

Use a spacer just smaller in diameter than the shaft and recouple the flanges with longer bolts and make up the bolts and press the shaft out of the coupling.

Sounds like an easy way to get the coupling off of the shaft. Why not temporarily refasten coupler to marine gear and rotate by hand while watching shaft at the strut?

 

[RT Firefly]

Greetings,
Mr. tiku. I fully agree with Mr. Tom B. regarding not using brute force (Large pipe wrench-Mr. bglad's suggestion) to straighten your strut. Go gently my brother. It could very well be that a professional WILL use brute force but if any damage to the hull or fasteners is done it will be the pro's responsibility NOT yours. Maybe a course of action would be to remove the offending strut and use some sort of hydraulic press to straighten. So, when you stuff your strut you can strut your stuff.

 

[psneeld]

Sounds like an easy way to get the coupling off of the shaft. Why not temporarily refasten coupler to marine gear and rotate by hand while watching shaft at the strut?

Easy until you bend or break the flange on the back of the tranny...that's expensive unless you repair it yourself.

I always recommend cut off a solid coupling if it doesn't come off easy without too much force...and replace with a split coupling. Requires a machine shop to do but they check your shaft for being straight also.

 

[bglad]

You certainly wouldn't be wrong to hire a "pro" but the parts are fairly light weight and the amount of force required to love them back in shape may likely be less than you think. I base my assessment of the equipment size by the fact it is a VP cone clutch transmission, four bolt coupling flange and guessing 1.5" shaft. The strut barrel is not much larger than the shaft so relatively light. I wasn't figuring the force required would fall into the "brute" category.