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Old 29-03-2016, 05:58   #31
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Re: easiest way to change engine mounts

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Originally Posted by Sandero View Post
You may have to "twist" the engine to get the couple plates to perfectly align. The mounts will have at least one slotted hole so it can be rotated.

The alignment can be tricky especially if you have removed all the mounts and have the engine suspended or resting on a soccer ball.

The method I described above essentially gets the engine back where it was... BECAUSE YOU NEVER ACTUALLY MOVE IT VERY MUCH. This saves you lots of headaches and alignment problems.

When changing one mount at a time... the remain 3 can EASILY support the engine... but as mounts are "soft" it WILL drop a bit hence the blocking/shims. Also couple alignment is a much simpler process since the engine is basically in the same place... with only new mounts.

I can't say the system I used will work for every motor installation. It worked for mine and I don't see why others would not be similar enough for this system to work.

If you don't HAVE TO suspend the motor.... or support it on soccer balls... then the method described is the way to go... actually easy peasy just takes time and the right tools.
Excellent !

Now I know why am returning to CF.
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Old 29-03-2016, 06:19   #32
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Re: easiest way to change engine mounts

Apologies for the typos and synatax errors... I didn't proof before submitting...

Vibration at certain revs can be from any number of causes... I assume this vibration ONLY occurs when the shaft is turn and prop spinning. If the vibration occurs in neutral then it has nothing to do with the prop or the shaft.

The vibration can be caused by other causes of imbalance... and who knows... it could be a faulty mount which can lead to the engine shifting a bit and SEEM like a shaft/prop issue and it's just an coupling alignment issue.

You need to first run the engine with no prop and see if the vibration occurs... assuming the mounts are reasonably OK. If they are old... you certainly can change them... you might have a sheared bolt on the mount and can't see it until you take them off!

Once you have the engine back on new mounts run it and see if there is vibration... If not do the alignment. Hopefully you can get at the engine mount alignment bolts without having to take bits off the engine which I have to do...

I strongly advise to NOT remove all mounts at the same time and support the engine on a soccer ball... WHY??????????????????? Mounts should dis assemble, brackets come off the engine... you don't need to raise it and might not even have the room to raise it. I didn't

Good luck.... tell us what the vibration was from..
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Old 29-03-2016, 06:53   #33
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Re: easiest way to change engine mounts

I'll of course change the mounts one at a time, I see no advantage of trying to do more than one at a time.
Mounts appear to be old, I wouldn't be surprised if they aren't original to the boat, so they need to be changed, and if new mounts and an alignment doesn't fix the vibe issue, then I'll check shaft run out with a dial indicator. I hope the yard did check for straightness when they had it out as that is just too easy to do, and I would hope be SOP, like checking a head you have off to see if it's flat before you put it back on.

It only vibrates in gear, it is a drive line vibration, it's worse in forward than reverse, I assume due to the gear ratio, reverse spins slower than forward.
Real simple system, it can only be a couple of things, I thought worn Cutlass, but that was replaced
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Old 29-03-2016, 07:47   #34
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Re: easiest way to change engine mounts

Sorry if this has been covered... don't forget to check prop for balance.
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Old 29-03-2016, 09:50   #35
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Re: easiest way to change engine mounts

I just did an an alignment on my engine and would like to mention some observations.
My engine had some vibration but what was most annoying was a knock at certain rpm after disconnecting the flange I noticed very little misalignment from a clearance around the flange stand point which made me think I would not be doing much good, but after sliding the prop shaft back far enough to disengage the centering part of the flange there was a significant height difference, by holding the shaft in the center position in relation to the shaft log it was obvious that the engine had settled slowly over the years By raising all the mounts about a 1/2 inch and then engaging the centering part of the flange and making final adjustments I was able to totally eliminate the noise. Yes it still has certain rpm that have the shakes but it's a Yanmar
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Old 29-03-2016, 09:58   #36
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Re: easiest way to change engine mounts

each one is different, but will use the same approach to each.

I like to use a nylon come along and just lift each side.

Leave the nuts on the top of the studs when lifting to keep the engine from coming all the way off.

measure from the beds to the hard mount and get the new installation as close as possible for final alignment. keep you side to side in the grove where the old ones were. If painting the beds, don't forget to mark this on the old mount to know where they were sitting before.

The first thing you do is unbolt and slide apart the shaft coupling. If you have a long shaft, make sure to support the shaft at the same height it was before unbolting. coat hanger, wood, etc.

When I can, I will unbolt the hard side from the engine, that way don't have to raise the engine over the stud, but that is about 50/50 on access or bolt condition.

Take your time and use common sense. Especially take your time on final alignment.
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Old 29-03-2016, 10:29   #37
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Re: easiest way to change engine mounts

Quote:
Originally Posted by Sandero View Post
Apologies for the typos and synatax errors... I didn't proof before submitting...

Vibration at certain revs can be from any number of causes... I assume this vibration ONLY occurs when the shaft is turn and prop spinning. If the vibration occurs in neutral then it has nothing to do with the prop or the shaft.
I disagree with that as a blanket statement.

I have dealt with a couple long shaft boats where idle vibration is the result of the shaft. Primarily when the owner has switched to a PSS packing in lieu of traditional packing assembly. The PSS allows the vibration to continue to the cutlass whereas the traditional would take up some of the vibration. Harmonics change drastically and the shaft is allowed to vibrate in longer motions/waves. That would translate into changed harmonics over the RPM range as well.

Add a worn cutlass to the mix and it only gets worse over time.

Easy to determine. Disconnect and hang the coupling, then start the engine and see if the idle vibration has lessened.

Harmonics are not fun. I switched out combinations of DF mounts 3 times once before I got it where I wanted it over the RPM range I liked to run at and move the natural sweet spot. But there are so many factors to check prior as far as the overall condition of everything, including things you would not think of like a lift muffler rattling where the owner thought it was vibration and mounts.

If we are talking about a Yanmar, it is more likely the mounts as they do not last as long as others like R&D, but they do a better job on a wider range for harmonics in my opinion.
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Old 30-03-2016, 02:37   #38
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Re: easiest way to change engine mounts

I once had to re-position the engine on its mounts when I was way out in a gunk hole with no access at all to special tools, jacks, or anything. (Had managed to get the stern warp wrapped around the prop, and bent the shaft bracket to one side - so new angle on shaft required new angle of engine to avoid mangling the shaft and coupling.) So, what to do? Easy! Put several turns of rope from engine to main boom (protective wrap over boom first), then use the topping lift to lift the boom and engine. Plenty of strength and purchase for the task. Obviously, this wouldn't work if you can't take a rope (or chain) directly up-and-out from the engine.
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Old 30-03-2016, 18:20   #39
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easiest way to change engine mounts

OK they are done.
First a soccer ball will work just fine, if I had gotten a decent pump. Pump I got was a piece of crap and the hose on it busted. If I had gone to the hanger and gotten my bike pump, it would have worked.
What I did was go to Lowe's to get a 2X4 to use as a pry bar, and got a 30" crow bar. Chose a 1X3 piece of red oak Instead as it would fit better and Oak is strong. Just pried things up, took the old mounts out and used my calipers to measure distance between the two nuts and set the new same, oh and outlined the edge of the mount before loosening with a Sharpie so new would go back the same.
Had to remove alternator and water pump">raw water pump to get the forward port side mount in and out, or maybe it could have been done with them in, but a whole lot easier to remove.
Alignment was perfect or as much as I could measure anyway which made me suspicious that somehow I didn't understand how to measure, but it's such a simple thing, how could you get it wrong?

Anyway just ran it up and no vibe at all, even at full throttle, so I guess that engine alignment I paid for wasn't done.

I'll take her out tomorrow and run her hard and see if vibe is truly gone or not, but I was getting 3350 RPM at the dock in forward, so I believe it's gone, before the vibe would start at 2300 RPM.

I believe if I had the patience the shim method of pieces of wood under the pan would have worked well too, I just went the primitive Pete method and pried it up and held it there until I got the old out and then new in.


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Old 30-03-2016, 20:25   #40
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Re: easiest way to change engine mounts

Glad to hear of your success.


S/V B'Shert
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Old 30-03-2016, 20:30   #41
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Re: easiest way to change engine mounts

11 years ago Cbreeze had a resonance about 2200 RPM with the Autoprop installed. New set of motor mounts solved the problem. FF 2015 and a similar problem surfaced. Problem is at much lower RPM. New mounts sitting on the galley counter. None of these problems show with the factory prop.

That AP must be twice the weight of standard and the polar moment of inertia must be many times. The Yanmar mounts have a low resonance frequency (note the engine movement while the engine spools down after shutting off). The rubber in the mounts is completely loaded in shear. That huge hunk of bronze will just point out any weakness in the drive system.
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Old 30-03-2016, 20:33   #42
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Re: easiest way to change engine mounts

Awesome! !!!

It was just crap mounts then with the vibe. ... you know. ... like a broken one in a car, but these weren't. ...

Soft or worn-out so they let the engine move out of alignment at your wiggly speeds. ....

Multiple crossed fingers to be completely resolved!

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Old 31-03-2016, 02:40   #43
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Re: easiest way to change engine mounts

That's a good result... aside from not supporting the engine on shimmed wood as you took them out one at a time... this was basically.... as far as I can tell how I changed the mounts one at a time...

All's well that ends well.
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Old 31-03-2016, 05:31   #44
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Re: easiest way to change engine mounts

It is of fundamental importance to have blades taking the same pitch, so you need a central gear to sync them.
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Old 01-04-2016, 15:31   #45
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Re: Easiest way to change engine mounts

so i have new mounts installed, not a bad job. lined the shaft up with tranny plate. don't know if i was just lucky but after 30 minutes of small adjustments to new mounts just slipped into place. 5" disc, so 1/1000 per " to gap the 2 plates and it just seems to fit. Now here's the question, all seems to work well, fits good, I can now turn the prop shaft by hand behind the tranny, outside just 2 fingers to turn the prop. Could not do this before, does this sound right to someone who knows what they are doing? also, when i installed the new mounts, i measured the bolts length to the old ones and the motor ended up 1/2 inch higher, i am assuming because the new rubber doesn't crush like the old ones (prob 30 years old). so question is, have i forgotten anything or is there something else i should be checking? boat is on the hard, will try this weekend to run it and see how much vibration but looking for any issues i can expect.
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