engine mounts, diagnosis?

[dial-a-monkey]

Yanmar 3jh4E 1100 hours 8 years old with yanmar 100 & 150 mounts.

Is there any way to check if my engine mounts need to be replaced? If they have gone 'soft'?

They have not collapsed, the space on top of the rubber is more than a finger and the same on all 4.

Revving the engine in neutral above 2200rpm most of the vibration smooths out. When in gear there is a lot more vibration which is why I'm concerned.

I found on the internet some yanmar mounts have lasted 15! years despite the recommended service period of 4 years.

There is more fore and aft vibration in gear than 6months ago but it is still smallish.

Dragging the propeller in neutral shows some vibration which I wonder if this means the prop shaft is bent?

Engine Flange alignment is within .03mm and I just replaced the propeller cutlass/sleeve bearing.

I read that the engine bracket+mounts should not move more than 3mm when revving hard from neutral to max rpm and then the same in reverse

Any input would be very much appreciated especially considering the price of OEM engine mounts

 

[Mrnotming]

is there any sound accompanying the vibration?like a tak tak tak?
how would you describe the vibration? Is it like a wheel unbalanced in a car?
Sometimes even with a minimal clearance as you you have checked (all around the periphery of the half coupling),the shaft may have come to bear unfairly on the actual stern tube, ie no longer concentric.So if the mounts can be adjusted easily, decouple the half coupling, support the shaft so that it is central in the tube.Not easy afloat, but it shoud be possible to apply directional pressure to the shaft and settle on a fair position without any binding.Chock off the shaft so it cannot fall or move, and then manoeuvre the engine little by little until the flange measures equally all around, i.e. top, bottom and both sides should trap the gauge with the same pinch effect.
bolt up the flange, tighten the mounts without disturbing the set.
If the problem has gone away, you have done a good job.
If the shaft proves to be bent, these suggestions will be useless except they will have to be performed after the shaft has been fixed.
There could also be a chunk out of a prop blade, so perhaps stick head underwater first?
Hope its the minor matter of centrally aligning the shaft in the tube(not a lot of clearance here sometimes), and folk have been known to remove a bearing behind the stuffing box,if the shaft length is shortish and supported well at the outer end.
Again I am presuming a length of rubber reinforced hose between stuffing box and actual stern tube, thrust perhaps being taken by the gearbox.If a plummer block supports the stern tube, these recommendations are thus useless as well!

 

[dial-a-monkey]

Thanks for the suggestions.. Hmm interesting suggestion about the shaft not being correct in the stern tube..when I unbolted the half coupling I noticed it tended to align lower than it would be when the couplings are joined.. But this I didn't make sense as I would not expect the mounts to raise..or the mounts on the lighter front of the engine to drop..I have a dripless Volvo stern gland so checking if the shaft is centered won't be possible as I'm in the drink at moment..the last time I had the prop off the shaft was very slightly high in the stern tube.

 

[dial-a-monkey]

There isn''t any obvious metallic noise but good idea I check..I have checked the prop several times looking for anything odd but nothing is obviously wrong, once by sticking my head under while motoring with a diving mask..

 

[Daydream believer]

I was worried about my forward engine mounts -having run over 3500 hours in 13 years.
So I have bought one mount as a a spare in the hope that if I had a problem one would break first ( It would be very unlucky for 2 together) & I could replace that which would get me home then I could sort the problem
I have a saildrive

 

[Mrnotming]

Ah! A saildrive, different story altogether!

 

[dial-a-monkey]

Another suggestion that might be helpful for others with a similar question :Get someone to turn on the engine while you watch the engine mounts, if there is a problem with a specific mount it should be obvious.

 

[Birdseye]

Yanmar 3jh4E 1100 hours 8 years old with yanmar 100 & 150 mounts.

Is there any way to check if my engine mounts need to be replaced? If they have gone 'soft'?

They have not collapsed, the space on top of the rubber is more than a finger and the same on all 4.

Revving the engine in neutral above 2200rpm most of the vibration smooths out. When in gear there is a lot more vibration which is why I'm concerned.

I found on the internet some yanmar mounts have lasted 15! years despite the recommended service period of 4 years.

There is more fore and aft vibration in gear than 6months ago but it is still smallish.

Dragging the propeller in neutral shows some vibration which I wonder if this means the prop shaft is bent?

Engine Flange alignment is within .03mm and I just replaced the propeller cutlass/sleeve bearing.

I read that the engine bracket+mounts should not move more than 3mm when revving hard from neutral to max rpm and then the same in reverse

Any input would be very much appreciated especially considering the price of OEM engine mounts

More likely than soft is that they have become delaminated from the metal bits. Put a crowbar under the sump and lift the engine enough to see if daylight appears between rubber and metal. If not then sometimes one mount sinks a bit more than the others leaving the engine effectively supported by 3 mounts. So slacken off the nuts and then use the crowbar to lift the front of the engine and see if gaps appear on one side but not the other.

 

[sailorman]

I bought my Nanni look alike from http://www.avindustrialproducts.co.uk/silent-marine.htm well under 1/2 price for the same thing