Yanmar 2gm engine mount rubbers

[Sanfelice]

Hello fellow top hatters

I have an inboard yanmar 2gm 15hp and the rubber inserts in the engine mounts are gone. I'm wanting to replace them and just wondering if anyone has had any experience with doing this.

I have cracked all the nuts and am wonder if I will need to disconnect the shaft from the back to be able to lift the engine over the mount bolts.

[lockie]

You must disconnect the shaft coupling otherwise you'll also be dragging the prop shaft up. Unless it's been disconnected in the last year or so, don't be surprised if corrosion makes difficult. If so, spray the threads liberally with penetrant and wait a day or so, and use sockets or rings spanners so you don't strip them. I ended up using a ring spanner on the bolt-heads, braced against the hull, and for the nuts a socket with water-pipe cheater (extender) on the handle. Use lots of Lanox when you reassemble so it's less corroded and easier to undo next time.

Cheers, Graeme

[Sanfelice]

Cheers Graeme for the quick response.
I'll do that.
I have managed to free the shaft from the engine. This is not a fun job at all... got three of the 4 mounts off the last one is being a prick of course

[Phillip]

So your engine mounts are gone!

"Why" is the real question?

If you have engine mounts that have failed you MUST check the polyflex connector between your gear box and the shaft if you have one.
They do work harden and really only last between 5 and 10 years.

I've just been through this exercise and the polyflex was that bad that i've been chasing mounts [3 sets] and a prop shaft and the previous owner ? sets and one prop shaft also.
But I have replaced the polyflex connector and its been a lot better in fact "problem solved!"

You may also have to replace the cutless bearing on the prop shaft. Has yours been knocking?

[Sanfelice]

Hi Phillip
Yes the gutless bearing does need replacing but as you can see from the photos the rubber inserts seem to have almost melted. I'm not sure when they were put in last but it could easily be between 5-10 years. It didn't have a polyflex connector. I did notice that there was only 3 bolts on the shaft to gear box connection that should have 4 and they were pretty much finger tight which is a worry! Do you think this may have a effect on the general wear of the rubber?

[Phillip]

Can you post a photo of your gear box to prop shaft connection and your prop shaft back to where it exits the hull?

I'm not an engineer but I do think if one bolt was missing, there lays 'one' of the causes of your problems.

[lockie]

Philip;

Where did you learn about the work-hardening? Polyflex told me this does not happen. If it actually does, I'll definitely replace mine!

Cheers, Graeme

[Phillip]

I've just done mine last October.

In fact after talking to the previous owner I found that he had spent thousands [ripped off] getting a new shaft, cutless bearing and engine mounts back in around 2000.

Since I've owned Seaka I've replaced three sets of engine mounts and one shaft and two cutless bearings.

All of the work [new shaft, cutless bearing, engine mounts] was done before they discovered that the polyflex connector was causing the engine to flop up and down!!!!!!

That was the cause of all the problems!!!! Seems that the connector had been in since the new engine install around 1995.

Since I replaced it all up in Mooloolaba on the way home to the Camden Haven Inlet [Laurieton] I've had no problems at all and is it soooo quiet now!!

[lockie]

Ok Phil, thanks for that, very interesting. I have replaced Shakti's mounts and cutless and have done the alignment 4 or 5 times, and have been greatly disappointed by the lack of improvement in smoothness.

I spoke to a local supplier (Luxfords) who confirmed and said yes they can harden over a very long period of use.

Interestingly my disk is the red one, which has a torque rating of 496 Nm. This is about 7 times the required torque (the 2GM develops 32 Nm max times 2.21 gearbox ratio = about 70Nm). So it is too stiff by a huge factor according to the Polyflex data, and I suspect it is not much better than a metal-to-metal connection.

Polyflex also list a green disk listed rated at 230Nm, which is about 3 times actual torque. That's still pretty stiff, but presumably would provide improved flex and isolation. if I do get around to replacing it that's the one I'll buy. Just out of interest Phil, what disk did you put in?

Now back to the topic with apologies to the OP for this (to me) most interesting hijack!

Cheers, Graeme

[Phillip]

I'll have to find the polyflex book for more details, but it was engineered for my 10hp Nanni.
Its red.