Engine Alignment

[jviss]

Regarding strut alinement. I made up a metal slug that fit snugly in the cutlass bearing and was a little longer than the cutlass bearing. I then bored a 30 caliber hole in the center along the axis. In this hole I slipped a laser tool for bore siting a rifle. If the laser is good enough to hit the bullseye at a hundred yards it should be good to hit the center of the hole in the trough hull where the propeller shaft goes a couple feet away. I believe the strut and cutlass bearing are adequately aligned.

That's excellent. I was thinking the same thing, I have a laser cartridge in 5.56x45. I was thinking of aiming it from a slug fitted into the cutless bearing and shining it through the packing nut, but same idea.

So, I guess the strut is straight. A mystery why the alignment is off so much. It must have been built that way, though.

 

[Dan Anthony]

I just read RJM's post. I already have shims under my mounts, these shims are easily removed. Perhaps I could fabricate a shim and using countersunk bolt heads bolt the shim down and then have holes drilled and tapped where they I think they should be. The shims already under my mounts are thick enough I could recess a regular lag bolt head below the surface. That may indeed be easier. Thank you. I'll noddle this idea a bit.

 

[Ralph Johnstone]

What else could it be???

I'm assuming (what else can I do ?) that the bend was aft of the shaft log so it's even more likely that a misplaced sling caused the bending. @Dan Anthony had the bend removed before he started the alignment job so with all the work the machine shop did, everything related to the shaft was true when he started. From that point on , he should have been looking at a textbook alignment with no problems. Didn't happen that way.

I still believe there is something else rotten in Denmark which has not yet been detected. I'll see if I can draw out the dimension for the hole locations as Dan has given above. I'm a picture kind of guy.

 

[Ralph Johnstone]

When I first removed the original mounts they were bedded with what I believe was 4200.

Ahah! So there IS something rotten in Denmark.

There is no way I can see the Hunter assembly plant using 4200 or any other sealant/glue under the mounts. This is the work of an amateur. A future alignment job could not be done without a lot of additional removal. Come to think of it, what if the 4200 started to set before the amateur alignment was complete. OUCH ! The use of a sealant does not affect the alignment in any way but when I see this, I've got to wonder what else this person may have got up to on the engine before it was hammered together and the bill presented. I always come back to the same old mantra, "the prop coupling was destroyed when you got the boat and I've never heard of that before"

My mounts had nothing under them and are sitting on what looks exactly like 3/8" Starboard which sits on the stringers.

I still encourage you to pump the previous owner for any information you can get about work done on the engine by previous mechanics.

I did some more research. Per the Yanmar 3GM30f data sheet the front engine mount hole should be 192mm from the face plane of the crankshaft v-pully.

Could you post any material you have on this as I'd like to draw this up to see how the longitudinal differences affects the alignment ? Thanks.

 

[MikeHoncho]

This is what I used to get around sheard lag bolts when I was changing my motor mounts and replaced the starboard shims with aluminum. It worked great. Maybe something like this will work for you rather than moving your engine placement.

Brilliant!

 

[Screen Saver]

Firstly, Like everyone else here, I highly doubt Hunter put this in the wrong place, but strange things have happened . Hunter did put the jig for my water tank filer in the wrong place, drilled it through the deck even and then realized, filled with epoxy and attempted to redo the Deck pattern and made a bad job of it.. Fact, and in factory my boat.

Back to your problem
At the beginning you stated: the flange more or less fell off in your hand the key was worn etc. So this establishes one of two things for certainty.

Either the alignment was out before you started, or the nut on shaft came lose. You did not mention whether the flange bolts were wired and or tight, whether the shaft had its locking tab on the nut. If the nut holding the flange came lose even with good alignment, I would expect the results you saw. However if the alignment was out before you started I would expect the flange bolts would have suffered, ie would have been lose, perhaps elongated their wholes. I’m going to assume (tell me if Im wrong) the flange bolts seemed in order.

Hunter getting it wrong in the factory ( I cant say it is impossible given my earlier statement) but that and no one having found or fixed it before now I would say is my absolute last option..

In spite of matriculas effort and detail you have shown and I apologize for the suggestion but I would be going for a self-inflicted wound.
I am struggling to understand “But the side to side wasn't even close, it was off by 1/4" “
and “In this hole I slipped a laser tool for bore siting a rifle. If the laser is good enough to hit the bullseye” for strut alignment. I don’t doubt you, I just don’t understand why the bullseye was not also ¼; or more… out.

In my own case I doubt I could get that much out by adjustment if I wanted to, which is effectively what your experiencing in reverse.

If the alignment was out prior to disassembly by ¼” I would expect the ware on the cutlass to reflect something near or at least indicative, with the ware on one side for example. Was that visible. But if the nut came lose on the coupling I would not expect any specific directional ware.

Also “When I first removed the original mounts they were bedded with what I believe was 4200. I saw no evidence that the mounts had ever been moved from where the factory put them. I've looked hard.”

Again not doubting you, but I have trouble accepting it has been out ¼” or so badly from new. How many hours are on the engine?

Any idea how many miles it has done ?

Do you know why the survey said to replace the old mounts, do you still have them, could it be these are different somehow by ¼” It seems some engine mounts differ between front back port and starboard. I have no idea what yours should be, or the differences, and assume you put back new ones for what you had and the way you had, but that doesn’t mean they were right when you started of course.

Also “All the original shims under the mounts are in the right place” So I don’t know your setup, and yep different boat model etc, but do you know why there are shims there in the first place. My mounts are adjustable as I assume most if not all are and yours look to be also.

Apologies if I have missed something obvious.

 

[RoyS]

I think you should take another look at your strut. Struts are easily damaged by your prop snagging a line streaming from your boat or from entanglement with a lobster pot. Or, as you mentioned, striking a log. It is possible that it is bent or displaced or perhaps someone replaced it with a different model or mis-aligned it upon re-installation. While aligning your shaft to the engine keep rotating your shaft by hand to check for binding in the strut bearing or interference with the stern tube. I suspect that the original builder utilized a custom jig to drill the motor mount holes in the stringers. Such a jig would utilize an unbroken shaft that ran the full length of the (not yet present) motor, through the stern tube, and on through the strut. Using that jig it is hard to imagine that the motor mount holes could be so misaligned. Something has changed and the strut is the most vulnerable of all the components.

 

[Dan Anthony]

Thank you everyone.
The new mounts are exactly like the original mounts. They should have been a direct drop it. The 420 sealant I mentioned was just at the bolt hole. Not completely bedding the motor mount. And like the photo
plastic (starboard) shims under the mounts.

We left off with the engine and prop shaft alinement slightly out of tolerance (.005") gap on one side of the flange. To get even this close I had to force and distort the motor mount rubber.
Yesterday I had some time. I loosened all 8 lag bolts holding the motor mounts to the stringers, gave the engine a good side to side shake. All four motor mounts moved freely. I started the alinement process again and once again ended up in the the same place, to get things aligned I had to stress the rubber mounts.
I removed the lag bolts from the front starboard mount. The base of the mount snapped aft a good bit. With this mount loose the engine was able to move enough to get the alinement much closer. But I still had to force the engine. So I removed the lag bolts from the aft starboard mount, its base snapped aft a little. With these two mounts loose I easily got the engine positioned. I marked the location of the base bolt holes then loosened the vertical alinement nuts and rotated the motor mounts so I could see the marks. The locations marked on the front mount were 9/16" aft and 1/8" inboard of the original bolt holes. The rear mount hole marks were just slightly aft of the original bolt holes but far enough aft I could not get the bolts back in. I also noted, which I had noticed when I replaced this rear starboard mount, the bolts were on an angle. The bolts were very much tilted aft, head pointed to the stern. These bolts appeared to have been badly installed. I saw absolutely no evidence of previous damage or relocation. So I cut some dowels, glued them up, and tapped them into the original bolt holes. I drilled new holes and reinstalled the mounts. A mere 7 hours after I started I had an engine aligned with the prop flange with a gap not exceeding .002", with force I could get the .0025 feeler gage in, the .003 gage simply would not slide in. The motor mounts are nice and relaxed and straight.

I then started the engine and shifted into forward, while tied to the dock. At first I though I had forgotten something because I could not tell it was in gear. Then I saw the stern dock lines were tight and there was prop wash. I went down to the transmission flange, felt and listened. No undo noise and no vibration. I had the boat out today and it is very smooth and quite.

Thank you everyone. I consider this project successfully completed. I know its a low probability that Hunter would make such an egregious s error but that's the only thing I can determine happened.

 

[MikeHoncho]

I just dealt with what I thought was going to be a bent shaft after hitting a small log. I had a sound that was like something was rattling on the inside of the hull during specific RPMS. I switched out the damaged prop for a not damaged, previously used one. The sound got alot worse. I dove on it a couple times and realized that the shaft was not bent but was aligned at the very bottom of the shaft log and any distortion (hard steerage under heavy throttle and a bent or out of balanced prop) caused the shaft to rub/rattle on the log causing what I was hearing. Rewind about a year earlier and I changed out the motor mounts and aligned the motor to the shaft to within 1 or 2/1000th . What I did not know is the packing nut on the end of the old shaft hose had been lowering and lowering over the decades what I was using for a alignment reference was a lot lower than it should have been. The hose is really stiff and difficult to move around. Conveniently (not) the new mounts were almost maxed out vertically so I had to replace the stack of shims with a 1/2 thick aluminum block, lower the motor down and raise the shaft up (using a wood clamp) about 3/16 of a inch. Just enough for clearance and no more noise. Moral of the story, using the shaft for alignment only gets you part way there when changing a bunch of stuff.

 

[Ralph Johnstone]

I consider this project successfully completed.

Just goes to show that clean living and an in depth "understanding" of shaft alignment can overcome almost anything. Glad the insertion of new bolt holes corrected the alignment and relaxed the mounts.

 

[jviss]

I consider this project successfully completed.

Thank you for following up and congrats on a figuring this out and remedying it. Also, thank you for the detailed account as you went along!

jv

 

[MikeHoncho]

Thank you everyone.
The new mounts are exactly like the original mounts. They should have been a direct drop it. The 420 sealant I mentioned was just at the bolt hole. Not completely bedding the motor mount. And like the photo
plastic (starboard) shims under the mounts.

We left off with the engine and prop shaft alinement slightly out of tolerance (.005") gap on one side of the flange. To get even this close I had to force and distort the motor mount rubber.
Yesterday I had some time. I loosened all 8 lag bolts holding the motor mounts to the stringers, gave the engine a good side to side shake. All four motor mounts moved freely. I started the alinement process again and once again ended up in the the same place, to get things aligned I had to stress the rubber mounts.
I removed the lag bolts from the front starboard mount. The base of the mount snapped aft a good bit. With this mount loose the engine was able to move enough to get the alinement much closer. But I still had to force the engine. So I removed the lag bolts from the aft starboard mount, its base snapped aft a little. With these two mounts loose I easily got the engine positioned. I marked the location of the base bolt holes then loosened the vertical alinement nuts and rotated the motor mounts so I could see the marks. The locations marked on the front mount were 9/16" aft and 1/8" inboard of the original bolt holes. The rear mount hole marks were just slightly aft of the original bolt holes but far enough aft I could not get the bolts back in. I also noted, which I had noticed when I replaced this rear starboard mount, the bolts were on an angle. The bolts were very much tilted aft, head pointed to the stern. These bolts appeared to have been badly installed. I saw absolutely no evidence of previous damage or relocation. So I cut some dowels, glued them up, and tapped them into the original bolt holes. I drilled new holes and reinstalled the mounts. A mere 7 hours after I started I had an engine aligned with the prop flange with a gap not exceeding .002", with force I could get the .0025 feeler gage in, the .003 gage simply would not slide in. The motor mounts are nice and relaxed and straight.

I then started the engine and shifted into forward, while tied to the dock. At first I though I had forgotten something because I could not tell it was in gear. Then I saw the stern dock lines were tight and there was prop wash. I went down to the transmission flange, felt and listened. No undo noise and no vibration. I had the boat out today and it is very smooth and quite.

Thank you everyone. I consider this project successfully completed. I know its a low probability that Hunter would make such an egregious s error but that's the only thing I can determine happened.

that awesome! before fixing my problem, I installed a Brunton Autoprop and that thing would clunk going into gear both forward and reverse. I thought it was just the larger mass of the prop and the moving parts (blades) adjusting. This was after installing the new mounts. After getting the shaft more centered in the log the clunk when away and I have a hard time telling it is in gear it is so much smoother. Its amazing how things work better when they are aligned right.