Finally got shaft aligned after engine rebuild within .005"

This was not easy. Ended up needing the front engine moved over to the left about 1/4 inch, so needed to plug and drill new holes. I kept thinking move the back over, but that just did not work out.
It has been out of alignment for years.
I was aligning it last year did what I could with it, and i kept thinking the shaft was bent for years. It might actually be bent a little, but if so, it is bent .005"

Then it is not just aligning the coupler faces, the shaft needs to be centered in the shaft log as close as possible. I found propping up the shaft with some wood blocks so it is centered helped me a lot, and also using a come along to lift up the engine so the motor mounts would slide over.

I think it was running before with at least 10 thousands out of alignment which was ok if the engine ran real slow. Since I almost always just run it low rpm, I never noticed much troubles, but last year, doing some high speed runs, I noticed the shaft gong crazy bouncing around some vibration and engine blowing some blue oil smoke, so early spring I hauled it up and rebuilt the motor.

What would you think having a coupling alignment way off your symptoms would be?

I removed my engine to replace the fuel tanks and rebuild the keel/bilge. When I re installed the engine, I found I could not get the alignment correct, no matter what I did the front of the engine was not low enough. I came to realize the alignment was never correct for 35 years (1500 hrs) and that is one reason why the transmission needed rebuilding. Shaft is OK (This is a new to me boat)

I jacked up the engine, removed the engine mount and started to remove stringer material to allow the front of the engine to lower to the needed position. Unfortunately, I found the stringers were rotted and needed replacement. That is now done and I will soon be drilling 8 new holes. I made templates for location, but will rough in the engine first to make sure I am in the ball park. My takeaway is many original installations may not be correct and low speed operation hides a lot!

yes, these trans are 2.57 to 1 , so shaft speed is lower, so definitely could hide issues.
Since I mostly go slow, I never noticed a problem.

I ended up filling all the holes and drilling new ones. For filling I used wood skewers with PL premium poly construction adhesive. The come along and crowbar and a 4x4 really helped a lot with alignment to slide the mounts around.

The reality is a lot of boats are running around with misalignment. Especially the older Chinese built boats. Which can be hard to get into and/or keep in alignment without some re-engineering.

That is why I recommend using a coupling like these: Marine Transmissions, Velvet Drive, Paragon, marine transmission parts, <marine transmissions>

Not a cure all by any means. But they will cut down on vibrations and protect your transmission.

Sounds familiar...In 2007 I had my 40' trawler repowered by a "reputable" Seattle boatyard. Because I were replacing the original engine with the same model the yard decided not to haul the boat -- big mistake! After installing the new engine they could never get the shaft alignment correct and held to the argument that "all boats have some vibration...so just live with it". And I did for many years until I finally decided it was time to find the problem and fix it. Long story short, after hauling and carefully inspecting every component of the drive line -- from prop to transmission -- it was discovered that the drive shaft was not centered in the log and was laying low (directed downward). After centering the shaft and raising the engine a bit on her mounts, everything came together! Because the boat was repowered in the water the original mechanics couldn't/wouldn't remove the shaft seal for fear of flooding. I wrote to the owner of the Seattle boatyard describing what had occurred back then but never got a response. My boat now runs smooth and is even a tad quieter

Finally got shaft aligned after engine rebuild within .005&quot;

Capt.Bill11 said:

The reality is a lot of boats are running around with misalignment. Especially the older Chinese built boats. Which can be hard to get into and/or keep in alignment without some re-engineering.



That is why I recommend using a coupling like these: Marine Transmissions, Velvet Drive, Paragon, marine transmission parts,



Not a cure all by any means. But they will cut down on vibrations and protect your transmission.

Click to expand...

I often wonder how much vibration is "normal". On my little Yanmar at about 1500 rpm I get a pretty good vibration going when in gear. Not rattling my beer bottle type vibration but noticeable for sure. I only notice it when speeding up or slowing down since that's not an rpm I run the boat at. Do I add this to my list of worries? ?

Funny how some pros sit back and giggle about absolute alignment on engines with soft engine mounts. You can see where the shaft slides in and out of the packing gland from idle to full power. And people are worried about a few thousandths alignment?


Sure, strive for perfect...no doubt most fall way short.


Engines develop vibration from much more than alignment...so unless those are all solved...finding perfect alignment is throwing darts.

When I first got the boat, I replaced all 8 mounts from Bushing's INC.
They sold direct to me.
I originally had 5/8 studs, I went to 3/4 studs for the reason you stated about the engine moving around under load. It is stiffer now than it was. I had to drill the mount engine holes bigger.

I dont know if being out of alignment how it affects the boat under power. How far out etc... but they all say got to be close to perfect.

The flexible couplers should help take up misalignment. Seems to me you could be a lot off with one of them and not have a problem.