Yanmar Engine Mount Replacement

[reflectionsv37]

In 2001 I had a new Yanmar 3JH3E engine and ZF Hurth HBW150 V-drive transmission installed in Reflections when I was in Panama. The dealer in Panama made a few errors and originally placed the 200 size mounts on the rear of the engine and the 150 mounts on the front of the engine. By the time I reached New Zealand my cutlass bearing was worn out and my new prop shaft was bent.

I was fortunate to find a knowledgeable dealer in Opua who immediately recognized the problem. First the mounts should have been matched side for side rather than fore and aft but the orginal installation only had mounts on the engine, nothing supported the transmission. This allowed the engine to move upwards at the transmission when placed under load and that was the cause of the cutlass bearing wear and the eventual deformation of my new prop shaft.

The NZ dealer moved the mounts to the correct location and added additional mounts to support the transmission. I now have 3 mounts on each side. 200's on one side 150's on the other side. I have had no further problems with cutlass bearings or bent prop shafts.

Unfortunately, after that change, I've been living with much more vibration in the boat. Much worse than when the engine only had 4 mounts. It was necessary to fiberglass addition supports to the hull to support the motor mounts for the transmission which I suspected induced some of this vibration.

After 4500 hours, it's past time that I replace the motor mounts and would like to do something about the noise at the same time. Since the different mounts, 200, 150, 100 are based on the weight they support, does it make sense that I might be able to change the 200 mounts to softer 150 mounts and change the existing 150 mounts to 100 mounts? Having 3 mounts on each side gives more support for the engine. Switching to softer mounts on each side might reduce some of that vibration while still supporting the engine and transmission with the same weight bearing requirements.

Anyone have any thoughts on this?

[NoTies]

Do you have 2 or more shaft bearings? Do you have a flexible coupling? How long since basic engine alignment was checked?
Psst, off to Aneityum again in 10 days. How are the Solomons treating you?

[GordMay]

See ➥ ENGINE MOUNTS

And ➥ Flexible Mounts

3JH2 series and 3JH3E
A&C 100
B&D 150

[reflectionsv37]

The prop shaft is only 4' long so there's just one cutlass bearing.I've been advised to avoid a flexible coupling with the V-drive. It is not an issue with alignment. It's just vibration from the engine whether it's in gear or not. I think the mounts are just too stiff for the weight of the engine. ANd the Solomons were a great place to spend cyclone season!!

And to GordMay. I've got another sheet that shows some different things when the 3JH3E is installed with the HBW150 V-drive. It shows either mounts on the front of the engine and on the transmission(4 total) or mounts on the both the front of the engine, rear of the engine and the transmission(6 total).

I'm going to do some experimenting when I get ready to change these. I'm going to remove the mounts on the rear of the engine and see if that helps with the engine vibration. If it does, it would be a confirmation that my mounts are too stiff. Having 6 mounts makes for a nice secure installation and I suspect Yanmar may have sent the 200 and 150 mounts due to the additional weight of the V-drive. I think switching to a softer set of 6 mounts makes sense.

Thanks for the replies!!

[NoTies]

Hey Gene, I've just done an install and alignment on the same engine & Vee drive in Vila. Mounts on engine only. Another thing to check is that one or two of the mounts aren't loaded up by the other mounts. If you have to back the adjustment nuts more than about 16th" before they run free then that mount is loaded and will transfer vibration.

[foggysail]

Picking a motor mount correctly involves a little work. All mounts that I am aware of are rated for the load weight. Further, you should have their attenuation curves that are directly related to the frequencies that need to be damped. Another gutcha here is that the mounts, vibration isolators have their own set of resonances which if not properly selected will result in greater vibrations.

To make all these concerns even worse, the mounts have to be rated not only for their load bearing capacities which are vertical forces, they must also be rated for the horizontal forces that will be applied to them as the propeller propels the boat forward.

The very worst example of motor mount installations are those that have adjustable heights. With those things, who knows how much horizontal forces the mounts are being subjected to....think of a fulcrum.

My old 30' Hunter sailboat had a factory installed 12HP single cylinder diesel whose pistion operated horizontally. The vibrations at particular frequencies caused my lifelines to resonate and they were vibrating over 6 inches at the mid points. I was able to get rid of most vibrations by replacing the mounts but you have to match the vibration characteristics along with both the vertical and horizontal force limitations to the engine's vibration frequencies and the horizontal forces resulting from propelling the boat. Not simple, just trying to get the engineering data on the mounts is a job in itself. Good luck-- I recommend replacing with the originals and hope for the best.

Foggy

[reflectionsv37]

Peter!!!

It took me awhile before I figured out who you were! LOL! Small world!

Way back, when I arrived in NZ, David the Yanmar guy came out to check on the boat. He had seen the prop shaft & cutlass bearing problem before. We were in a slip and had me put the boat in gear and we could watch the V-drive rise 1-2 inches when we gave the engine some throttle. That's why he said mounts needed to be on the transmission. Since the others were already in place we kept them.

I'm going to do a quick haulout at Liapari to replace a slightly worn cutlass bearing and throw some paint on a few bare spots. They tell me we'll be doing lots of motoring in Indonesia, so I want I don't want any problems, but I won't be changing the motor mounts here. I'm going to have Noel check the alignment and I'll take a look to see if any of those mounts are loaded up.

Was this a new install you just did? What motor mounts came with the engine? 200 & 150 or 150 & 100. My engine was much, much quieter when mounts were only on the engine, but I knew something was wrong when the cutlass bearing wore out in less than 6 months. I took my new prop shaft to put it on a lathe to see if it was straight. There wasn't really any need for that. It was bent badly enough it wouldn't even roll when laid on a table!

After 2 weeks, Gizo finally got a delivery of propane today which is what we've been waiting for. We'll start heading back towards Honiara tommorrow morning so I may be away from the internet for 2-3 weeks.

Thanks for the help and tell Susan we said hi!!!

[reflectionsv37]

Thanks foggysail!

When I get ready to do this, I have quite a few things I'm going to try. In this situation, the noise and vibration is pretty much constant at all engine speeds. It's just vibrating through the hull and I want to reduce or eliminate that when I replace the mounts. The first thing I'm going to try is to remove the rear engine mounts and see if the noise is reduced. That will give me an indication if the mounts are too stiff. If it doesn't quite down, it may be the glass work to add the mounts to the transmission that caused the noise in which case, there may not be much I can do about it. Nothing like owning a boat to keep your mind active and hands busy!!!

[NoTies]

The install is an existing engine that we overhauled. Looking back I see what you mean about the weight of the Vee drive. I think you're going down the right track. Check mounts for loading then if that doesn't produce results try removing the aft engine mounts.
We used 200 & 150s which were original equipment with the engine.
PolyFlex in Australia make well regarded engine mounts with direct replacements for Yanmar mounts, might be worth researching.
Susan asked me on the phone tonight if I was getting a new mailing address!!! I've been up in Luganville for a month and Noumea for 2 weeks before that for refit work on some island traders. Fly home tomorrow after completion so all good until weekend after next when I disappear to Aneityum to recover drifting dinghies and some jetty maintenance.

[reflectionsv37]

Thanks Peter!!

Make sure you check on those drifting dinghys in Aneityum! I hear it's a real problem there!! LOL! Were going to get underway today. Should have internet again in a couple weeks!

Gene

[foggysail]

Reflections--

Just another tidbit--- vibration isolators...and that is what motor mounts essentially are are rated by attenuation curves. If I remember correctly the rating are in DBs. My point, don't rate an isolator be how it feels, get the attenuation curves if possible.

[Suijin]

My Valiant 40 has the same transmission, and it's not supported, hasn't been for 27 years. It weighs 44 lbs, which is chickenfeed compared to the engine itself. I really think your problem is the mounts supporting the tranny, not those under the engine. The fact that the whole system moves when under load doesn't to me mean you need more points of support, it means that the existing mounts under the engine are not properly selected and installed. I would ditch the tranny mounts before I started taking off engine mounts.

I'm no expert, but I'd think that six fixture points, two of which were added "ad hoc", would introduce a whole pandora's box of harmonic chaos over four mounts under the engine alone.

[Kasala]

I have the same engine and transmission in a Coast 34. The engine had 5000 hours on it when we bought the boat and had cruised continuously for 12 years. The engine is mounted with four mounts on the engine itself with the 100/150 series mounts on their respective sides. I believe this compensates for the rotational pressure caused by the engine's torque. Right from the start the engine had noticeable vibration issues at certain speeds and when I watched the end of the shaft while under way (visible at the coupling) there was significant shaking. When I replaced the cutlass bearing (the original was badly worn) the vibration got much worse. I figured out the the engine was out of alignment laterally but due to the way the shaft mates to the transmission by the coupling going through the output shaft (V drive!) the normal way of using feeler gauges to check alignment was useless. There was sideways pressure on the shaft even though the engine was square to the coupling. When I jimmied the engine into alignment laterally and then aligned it on the mounts to square the coupling the vibrations went away. Could this be your problem? Cheers Doug

[delmarrey]

Originally Posted by reflectionsv37

In 2001 I had a new Yanmar 3JH3E engine and ZF Hurth HBW150 V-drive transmission installed in Reflections when I was in Panama. The dealer in Panama made a few errors and originally placed the 200 size mounts on the rear of the engine and the 150 mounts on the front of the engine. By the time I reached New Zealand my cutlass bearing was worn out and my new prop shaft was bent.


Anyone have any thoughts on this?

This is why I went with one of these >>>>
V V V
V V
V

.

[Kasala]

Sweet! Having had a backwards engine with a V drive for five years now it is something I would avoid in the future. The space allocated for the engine in the coast 34 can accommodate a smaller Yanmar (30HP) the right way round but the 3JH2 needed to be installed backwards. The shaft is under the engine and is quite long leading to lots of flex if it is not dead true. The Yanmar mounts are apparently quite soft which should insulate the vibrations but, if the engine is not dead true, allows quite a bit of flexing of the entire drive train. Before I resolved the lateral displacement issue the harmonics traveled right through the boat at certain speeds. Needless to say that the output seal on the transmission weeps while all this is going on. I could also say that the stuffing box is almost impossible to access. The exhaust hose can rub against the shaft as it passes under the engine where it is also exposed to any drips. With proper alignment and regular attention the installation is usable and the Yanmar engine itself has been trouble free. I love everything else about this boat but the engine installation has always been a challenge. I have resorted to over pitching the prop a couple of years ago which has given me a good 6 knot cruise at 2500 RPM but in theory has deprived me of the max HP as the engine will no longer achieve max RPM. Ironic as I am probably back to the HP range of the smaller engine which would have been a better fit. Yes, I am aware of the problems associated with over propping but in this case it is the lessor of evils. At 2500 RPM the engine is in the heart of its torque range, runs smooth and quiet and there has been no evidence of carbon build up. Specific fuel consumption has actually improved slightly. Piston and bearing mileage should also benefit from this. Time will tell. Congrats on your arrival in SF. We had a great time there a few years ago. Doug