Flexible or hard motor mounts for 3 mount Uiversal M35

A previous owner of my 87 Ericson 34 installed a Universal M35 using a 3 mount bracket. This engine replaced a standard 25 hp Universal. The bracket and mounts were the listed part numbers seen in the M35 parts book. A few years back while working on what was suspected to be a transmission problem (turned out to be a feathering prop prop problem), my mechanic said the mounts were too soft and could cause a transmission problem if the engine moved forward/backward,. I dont recall whether he meant they were worn or simply too flexible

He replaced them after he contacted an "official site" who said the mounts should be "hard" . Previous to the replaced mounts, the engine caused no harmonic rattles and was especially smooth. But after the new mounts were installed the engine now causes various harmonic rattles in various places in the boat at varying speeds. (Prop shaft and cutlass bearing were replaced last year and had no effect on the rattles)

I cannot tell if the mounts are identical to those originally used - cant see a part number. But the mounting holes are the same as original and they appear to look the same.

Are the M35 listed "flexible" mounts for this engine proper or are harder mounts preferred? Was it possible to get similar but harder - less flexible - mounts that looked the same? Or was it more likely that the original mounts were just worn and the standard mounts are expected to cause rattles?

Should I expect harmonic rattles?

After replacing the transmission on our boat I had several more vibrations and harmonic rattles than previously. The mechanic had done the engine alignment and said he had brought it to .004 of an inch, as if that should be fine. When I did some subsequent checking, the specs call for closer to .002. I redid the alignment myself and got it to .002 after much effort, and it did make quite a difference, getting rid of most (though not absolutely all) of the vibration.

If you haven't checked/redone the engine alignment, I would suggest that might be a place to look.

Frank

Frank, thanks.

Yes I am now at .004 also.

Were your vibrations variable based on engine speed? Mine dont exist at crusing speed, only at low to intermediate speed.

Since the vibrations occurred immediately after the new mounts were installed, it seems to me that hard mounts exacerbated any minor alignment problem.

Beyond the issue of alignment - important as that is - my question is whether "soft" or "hard" mounts are best and are there preferred mounts made currently.

My frustration is that the mounts are designed for several engine weights but look the same. See for example http://www.go2marine.com/product.do?no=85481F See the engine weights but the mount dimension is the same.

The M35 is 335 pounds. So would there be more vibration to the hull using the mount designed for 150 - 450lbs versus 450 - 750lbs I would think so. I have a feeling I have the mount designed for a heavier engine and thus vibration. for sure if there was no cushening at all there would be lots of vibration.

I don't know about the soft vs hard motor mounts. But when my alignment was at .004 I noticed vibration at various speeds. I could temporarily get rid of the vibration in most cases by varying the boat speed, but gradually the vibration became more apparent, leading to another change in speed, etc. This was very annoying, so I decided to tackle the alignment, and was pleased with the amount of difference it made. I still get a small amount of harmonic vibration around 4 knots, but no other vibration at higher or lower speeds, and even the 4 knot one isn't bad.

The universal engine spec indicates alignment should be at .002.

Good luck in sorting solving it!

Frank

FWIW I installed new engine mounts from Bushings Inc. www.bushingsinc.com The part number on one of the existing mounts was one of theirs, but not the correct number, according to their documentation. My engine was listed in their data and they had a recommended part number. Torresen had the best price, had them in stock.

I was able to get the alignment to within 0.002 after much aggravation. The vibration is all but gone but there is the occasional harmonic buzz from the pushpit gate, etc. Very smooth underway. You might want to call Bushings Inc. and get a recommendation.

Lastly I would assume that mounts are made in varying durometers for different engine weights, mount configurations, etc. Again, a recommendation can't hurt. The technology and specs could have changed enough that the old part number has been superseded.

RT

Problem solved

I talked to the manufacturer of the Universal mounts and Torrensen Marine (and others). My problem is that the mechanic installed gasoline engine mounts for gas engines up to 800 lbs. Westerbeke continues to recommend for the 335 lb M35 a DF D2205-2 engine mount either with 3 or 4 mounts. Always understand what your mechanic is doing and installing.

By the way Westerbeke itself was of no help. They listened but gave no real understanding or even sympathy.

I found the problem by seeing the marked mount number on the installed mounts. I also had the paper work for the proper mounts on the initial 1976 initial engine installation. However it is not easy to decode it because the Universal parts list shows a universal part number, not the actual mount number.

No wonder I had vibration.

So what are you going to do now? Is there any chance the mechanic will acknowledge that he used the wrong part, and install the correct ones at no extra charge?

Good luck!

Frank

Not a chance. His approach was stiff is better for the transmission and there is no changing some people.

I've ordered the mounts and will install them with some assistance.