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Old 24-05-2020, 10:10   #1
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Ok to reverse orientation of Yanmar mounts?

I’m trying to align my motor and need to move it ever so slightly to port, but the sideways slots on two mounts are already maxed out. A really easy solution would be to rotate those two mounts 180 degrees so the slotted holes are facing aft instead of forward. The mounts look symmetrical for/aft but I keep reading that they need to be oriented a certain way (without knowing what that way is). Right now all the slotted holes are facing forward. Does anyone know if I can just rotate them 180 degrees to get the range of motion on the slotted hole that I need? Thanks Click image for larger version

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Old 24-05-2020, 10:17   #2
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Re: Ok to reverse orientation of Yanmar mounts?

I don’t know, but it’s what I would do.
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Old 24-05-2020, 10:28   #3
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Re: Ok to reverse orientation of Yanmar mounts?

Good day,

Not sure if this will be of any use to you but when I recently replaced all of my motor mounts, twin engine catamaran with Yanmar 2gm20 engines, one engine had the slots facing forward and the other engine had them facing aft. The boat was built in 1993 and I am near certain they are the original motor mounts and they did not appear to cause any problem due to their mounting orientation. They just wore out due to age.

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Old 24-05-2020, 10:33   #4
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Re: Ok to reverse orientation of Yanmar mounts?

I don't think the rubber cares, orient them how ever works.
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Old 24-05-2020, 16:05   #5
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Re: Ok to reverse orientation of Yanmar mounts?

Quote:
Originally Posted by Cheechako View Post
I don't think the rubber cares, orient them how ever works.
What he said. It may matter swapping fwd & aft mounts as some have different hardness but rotating 180o is no issue
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Old 25-05-2020, 08:50   #6
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Re: Ok to reverse orientation of Yanmar mounts?

[QUOTE=Compass790;3147425]What he said. It may matter swapping fwd & aft mounts as some have different hardness but rotating 180o is no issue?

Yanmar has denser mounts on the side that compresses with torque load.
Not fore and aft.
If the OP needs more side to side movement they can lengthen the slots or reposition the mounts and drill new holes.
I'd suggest you dowel those previous holes, before redrilling.
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Old 25-05-2020, 09:07   #7
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Re: Ok to reverse orientation of Yanmar mounts?

- You don't specify which model Yanmar?
- In any event there is no problem ( apart from time and effort ) with rotating each mount 180 degrees.
- NB Many small Yanmars use mounts of different durometer ( rubber stiffness ) front and rear mainly because of the engine assembly weight distribution.
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Old 25-05-2020, 13:02   #8
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Re: Ok to reverse orientation of Yanmar mounts?

Hi, it's not a problem, I did it on my 2GM20 and it still going fine after 5 years. The orientation they are talking about is the fact the fore and aft mounts, although they look the same are in fact two different strengths of mounts, to compensate for the difference in weight and vibration levels between the fore part of the engine and the aft part.You don't say which model Yanmar you have but the 1GM10 the mount values are front 70 and rear 50, for the 2GM20 and 3GM30 its front 100 ,rear 75, and 3HM its 100 front and rear. The values are imprinted in the rubber on the sides of the mounts.
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Old 25-05-2020, 13:05   #9
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Re: Ok to reverse orientation of Yanmar mounts?

[QUOTE=Boatyarddog;3147848]
Quote:
Originally Posted by Compass790 View Post
What he said. It may matter swapping fwd & aft mounts as some have different hardness but rotating 180o is no issue?

Yanmar has denser mounts on the side that compresses with torque load.
Not fore and aft.
If the OP needs more side to side movement they can lengthen the slots or reposition the mounts and drill new holes.
I'd suggest you dowel those previous holes, before redrilling.
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That is incorrect, I am quoting from the Yanmar official Operating Manual. The different values are fore and aft.
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Old 25-05-2020, 14:51   #10
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Re: Ok to reverse orientation of Yanmar mounts?

[QUOTE=Martkimwat;3148059]
Quote:
Originally Posted by Boatyarddog View Post

That is incorrect, I am quoting from the Yanmar official Operating Manual. The different values are fore and aft.
You are right. I have just replaced them on my 2gm20f.
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Old 25-05-2020, 15:44   #11
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Re: Ok to reverse orientation of Yanmar mounts?

[QUOTE=Martkimwat;3148059]
Quote:
Originally Posted by Boatyarddog View Post

That is incorrect, I am quoting from the Yanmar official Operating Manual. The different values are fore and aft.
I believe the 'side to side' difference is applicable to the horizontal cylinder models. The OP is only talking a 180 degree flip of the same mounting, so it should be fine, after all, I don't believe they are not imprinted as to which end is fore or aft.
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Old 25-05-2020, 16:22   #12
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Re: Ok to reverse orientation of Yanmar mounts?

There are different durometer mounts for different locations, but that’s irrelevant he’s not charging the mount location, merely loosening the top nut and spinning them 180 degrees, so the aft port mount is still the aft port mount etc.
Unless I’m confused what he is asking.
Torque would seem to be the logical answer, on mine the harder mounts are on the starter side and I assumed the starter and heat exchanger made that side heavier.
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Old 25-05-2020, 16:33   #13
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Re: Ok to reverse orientation of Yanmar mounts?

Quote:
Originally Posted by a64pilot View Post
There are different durometer mounts for different locations, but that’s irrelevant he’s not charging the mount location, merely loosening the top nut and spinning them 180 degrees, so the aft port mount is still the aft port mount etc.
Unless I’m confused what he is asking.
Torque would seem to be the logical answer, on mine the harder mounts are on the starter side and I assumed the starter and heat exchanger made that side heavier.
I made the same assumption re 180o rotation

However I should have said SOME yanmars have harder rear mounts or said nothing as it doesn't apply to what he wants to do

It's seems logical on our Yanmar to have harder rear mounts as they support the gearbox weight. YMMV
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Old 26-05-2020, 04:05   #14
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Re: Ok to reverse orientation of Yanmar mounts?

Just went through that same issue a few months ago on a 1989 Morgan 50 with a 75hp yanmar turbo diesel ( forget model #) and there is some controvercy within the forums on the different hardness of mounts being used front and back or side to side. YANMAR CLEARLY! specefies it is 1 hardness on port side and and a diferent hardness on Starbord side. This is mainly on the turbo models and is requird to absorb th torque of the engine when shifted and throttled. Get them wrong and it won't be long before you replace them again. Your anser is YES you will most likley have to put them with slots vacing diferent directions there is a difference in holes to center of mount bolt. It makes no difference how they face slot wise but it does make a difference if your engine requires the 2 different mounts ( they all look alike but have diferent weight rating.) be sure you get the right ones on the proper sides or they eventually will rip out the rubber from engine torque. I used the R&G mounts, they are a much better quality mechaniclly bonded with heavy aluninm base and s.s. cap (not glued to steel like yanmars) and are direct replacement mount, cost is about the same as yanmar but a far better built mount.
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Old 26-05-2020, 07:41   #15
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Re: Ok to reverse orientation of Yanmar mounts?

For the the 3GM model, the different hardness is fore (75, I believe) and aft (100). As I recall, I don't think there was any difference in the orientation for each one and could have been flipped 180, as needed.
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