Drivesaver question

[Peter]

I'm thinking of addind a 'Drivesaver' between the trans flange and the prop shaft flange.
Does it move the prop back a distance equal to the Drivesaver thickness? My prop already seems pretty far back, maybe I should get the shaft shortened.
Lots of room for zincs anyway :-)

[Tim]

I'm thinking of addind a 'Drivesaver' between the trans flange and the prop shaft flange.
Does it move the prop back a distance equal to the Drivesaver thickness?

Yes. Most Drivesavers are typically 1" thick, so your prop will move back that distance.

Given the length of exposed shaft you already have, I would recommend having the shaft shortened. Fortunately, this is easy to do at a machine shop.

Regular Drivesavers are fine, but for the Yanmars with their soft, rubbery mounts, this kind is even better. I have a Yanmar part number of 104214-05450 for my coupling, but a quick search of Marine Diesel Direct doesn't bring up any hits for this part. Check with your Yanmar dealer to see if these couplings, or similar, are available. It's got heavy steel plates on either side of a hard, sacrificial rubber insert, and helps allow the engine to shake on its mounts the way they do without affecting shaft alignment or overly wearing the packing or Cutless bearing. This is also 1" thick.

[Peter]

I'll check with the local Yanmar guru for a Yanmar-built unit. I'm going to renew engine mounts also. Is it best to stick with Yanmar mounts or is there an aftermarket set that works better?

So I should shorten the shaft so that, with drivesaver installed, there should be room for the zinc plus 1/8" clearance on either side of the zinc.
With the prop hanging out there so far from the cutless bearing, shaft support is not optimum.

I guess I'll shorten the front end of the shaft, as there is only a simple cut and two set screw dimples to make, and the keyway slot to lengthen. I can get it checked for straightness at the same time.

Thanks, Tim!

[Tim]

Is it best to stick with Yanmar mounts or is there an aftermarket set that works better?

It's smart to replace your mounts, since the old ones lose their properties gradually over time.

The Yanmar mounts are unique in their softness, and "wiggliness". These properties seem to me to be important to calm the shakiness of the Yanmar engine at idle speeds. I would stick with the Yanmar mounts. They work well.

On the 2GM20F, the forward and aft mounts are different, with different moduli of elasticity, so be sure to use the proper ones in the proper place. You should have two marked "75", and two marked "100". They install counter to logic--I believe the 100s go forward, and the 75s aft. Or if it seems more logical the other way, then it's vise-versa. I can't recall exactly. In any event, check to be sure which go where first.

[Peter]

Good mount info, Tim, but my Yanmar is an older 2GMF 13 hp. Does the same info apply?
Thanks.

[Tim]

I don't know for sure. Changes in the Yanmar models were incremental, and I wouldn't be at all surprised if the mounts were the same. The GMF series is very similar to the later GM series, and the stock mounts I have seen in use seem to be the same...but I wouldn't assume so without checking first.

[Peter]

Finally got the engine out today and am ready to order new mounts and a flexible coupling. I'm sticking with stock Yanmar mounts.

I came across a reference to a Yanmar 104214-85450 flexible coupling that may fit.

Another reference was to a post of Tim's.
Tim, can you shed some light on this? I'm looking for the bolt circle size.
According to one distributor this is the correct part.

Thanks!

[Tim]

The 104214-85450 should be the correct part number for my coupling. My earlier post in this thread contained a typo that I only just noticed.

I don't think my coupling is as large as 6-5/8", but there's another flex coupling of that size, # 124770-85400.

I will try and get aboard the boat today to check out the bolt circle for you. I'd kind of like to determine the proper part number for my own purposes, too.

[Quetzalsailor]

There's a dandy Forum for your Yanmar. Here's the address: http://www.freeboards.net/index.php?mfo ... _post&st=0

The Yanmar guru is excellent.

[Peter]

I don't think my coupling is as large as 6-5/8", but there's another flex coupling of that size, # 124770-85400.

At first I thought the 104214-85450 was that size, too, but closer examination on my distributor link shows it to be 5 1/4". That would appear to match the one in your picture, Tim.
My 4-bolt circle is 78mm (3.07") If yours is the same looks like I might be in business with the # 104214-85450. It's listed on Torreson's site.

Quetzalsailor, thanks for the great link .... another source to mine :-)

[Tim]

My shaft coupling is 4" outer diameter, so I suspect the 3.07" bolt circle that you measured is the same as mine. I didn't have a good way to actually measure mine.

The flex coupling is 5-1/4" in diameter, which matches the 104214-85450 part number that I have in my records.

[Peter]

Thanks for checking, Tim!